PR-437
Horticulture
Faculty
Sharon Bale
Paul Cappiello
Win Dunwell
Richard Durham
Bill Fountain
Bob Geneve
Dewayne Ingram
Robert McNiel
Technical Staff
Shari Dutton
June Johnston
Sharon Kester
Kay Oakley
April Satanek
Dwight Wolfe
Farm Staff
Darrell Slone
Janet Pfieffer
Dave Lowry
Students
Steve Elkins
Bailey Hale
Philip Gonsiska
Jenny Heringer Vires
Reed Pirain
Delia Scott
Agricultural Economics
Faculty
Tim Woods
Agricultural Engineering
Faculty
Richard Gates
Richard Warner
Students
Erin Wilkerson
Agronomy
Faculty
Timothy Phillips
A.J. Powell
Entomology
Faculty
Monte Johnson
Daniel Potter
Michael Potter
Technical Staff
David Held
Students
Tyler Eaton
Jerome Gels
Philip Gonsiska
Michael Rogers
Plant Pathology
Faculty
John Hartman
Lisa Vaillancourt
Technical Staff
Paul A. Bachi
Julie Beale
Ed Dixon
Bernadette Amsden
Students
Jennifer Flowers
Fanny Moine
UK Arboretum
Director
Marcia Farris
Grounds Manager
Susan Capley-Vinton
Students
Kevin Abell
Michael Coy
Ryan Pfieffer
Delia Scott
Kris Stone
This is a progress report and may not reflect exactly the final outcome of ongoing projects. Therefore, please do not reproduce project reports for distribution without permission of the authors.
Mention or display of a trademark, proprietary product, or firm in text or figures does not constitute an endorsement and does not imply approval to the exclusion of other suitable products or firms.
The faculty, staff, and students in the UK Nursery/Landscape Program are pleased to offer this 2000 Research Report. This is one way we share information generated from a coordinated research program involving contributions from several departments in the College of Agriculture. The report has been organized according to our primary areas of emphasis: production and economics, pest management, and plant evaluation. These areas reflect stated industry needs, expertise available at UK, and the nature of research programs in neighboring states and around the world generating information applicable to Kentucky. If you have questions and/or suggestions about a particular research project, please do not hesitate to contact us.
Although the purpose of this publication is to report research results, we have also highlighted below some of our Extension program and undergraduate and graduate degree programs that are addressing the needs of the nursery/landscape industries.
Extension programs targeted to Kentucky's nursery/landscape industry include highly visible activities and some more subtle ones. The statewide and area educational conferences and seminars are probably the most visible. Publications, videos, slide sets, newsletters, articles in state and national industry magazines, newspaper articles, radio spots, and television programs are important, visible elements of our Extension program. However, training for county Extension agents so they can more effectively serve our clientele, the Plant Disease Diagnostic Clinic, soil-testing and interpretative services, and problem diagnosis and solving services are more subtle activities. We are delighted to see that the outreach capacity of the Arboretum on the UK campus increases each year for the industry and consumers.
Although there are many facets of the Extension program conducted by the team of subject matter specialists and county agents, our Home Landscape IPM Program and County Extension Agents for Horticulture are highlighted this year.
A home landscape integrated pest management (IPM) Extension program has been initiated by Richard Durham and William Fountain, Department of Horticulture, John Hartman, Department of Plant Pathology, and Monte Johnson, Department of Entomology, with funding from the Kentucky IPM Program and the UK Nursery/Landscape Fund. The overall goal of this project is to increase awareness in the general public regarding integrated pest management practices appropriate for the home landscape. During the first year, radio scripts have been developed and are being released to county agents for use in local radio programming or modified for release in newspaper columns or as factsheets. An Internet site <http://www.uky.edu/Ag/Horticulture/landipm/index.htm> was developed to highlight the program. An instructional video will be released in January 2001 for use in county and multi-county meetings and in Master Gardener training. The initial emphasis for this program has been trees and shrubs but will be expanded to encompass other aspects of the home landscape, including herbaceous plants, fruits and vegetables, and turf. This IPM Extension program has the potential to draw favorable attention to Kentucky landscape industries and help expand the market through consumer education.
The number of County Extension Agents for Horticulture has increased from three to 17 in the last decade due to the significant demand for horticulture educational programs at the county level. Each of the 120 counties has Extension agents for Agriculture, Family and Consumer Sciences and 4H/Youth Development who are cooperatively funded by state, county, and federal funds. Several of the general agriculture county agents are excellent horticulturists and have served our industries well for many years. Additional agents, such as those specializing in horticulture, are funded entirely by the county. The horticulture agents are primarily located in counties with a large population center, and they target a major portion of their programming to consumers, primarily homeowners. A portion of their time is invested in the educational programs and service support for commercial horticultural industries. Although educational opportunities and the size of each horticultural commodity differ among counties, the commercial landscape horticulture industry is important in each of these counties.
It is important to note that the County Extension Agents for Horticulture are part of the team of faculty, staff, agents, and students addressing horticultural opportunities through education and research. You see many of them working at the KLI Conference and Trade Show and other events. However, I wanted to introduce them to you again here. They are:
Boone County—Michael Klahr
Campbell County—David Koester
Daviess County—Annette Meyer
Fayette County—Candace Harker
Franklin County—Edie Greer
Hardin County—Amy Aldenderfer
Henderson County—Thomas Brass
Hopkins County—Amy Fulcher
Jefferson County—Donna Michael (KSU)
Jefferson County—Vacant
Kenton County—Don Smyers
McCracken County—Kathleen Keeney
Nelson County—Robbie Smith
Pulaski County—Beth Galloway
Shelby County—Tim McClure
Warren County—Michelle Johnson
Woodford County—Patricia Savage
The Department offers areas of emphasis in Horticultural Enterprise Management and Horticultural Science within a Plant and Soil Science Bachelor of Science degree. Following are a few highlights of our undergraduate program in 2000:
The Plant and Soil Science degree program has more than 110 students in the Fall Semester of 2000, of whom almost one-half are Horticulture students and another one-third are turfgrass students. Six Horticulture students graduated in 2000.
We believe that a significant portion of an undergraduate education in horticulture must come outside the classroom. In addition to the local activities of the Horticulture Club and field trips during course laboratories, students have excellent off-campus learning experiences. Here are the highlights of such opportunities in 2000.
A complete list of students and student activities can be viewed at <www.uky.edu/StudentOrgs/Horticulture>.
The demand for graduates with a M.S. or Ph.D. in Horticulture, Entomology, Plant Pathology, Agricultural Economics, or Agricultural Engineering is high. Our M.S. graduates are being employed in the industry, the Cooperative Extension Service, secondary and postsecondary education, and governmental agencies. Last year, there were seven graduate students in these degree programs conducting research directly related to the Kentucky nursery/landscape industry.
Graduate students are active participants in the UK Nursery and Landscape research program and contribute significantly to our ability to address problems and opportunities important to the Kentucky nursery and landscape industry. For example, graduate students as well as undergraduates presented research results at the Southern Nursery Association's Research Conference in Atlanta, and several will present posters summarizing their work at the 2001 Kentucky Landscape Industry Conference and Trade Show.
Production and Economics
Passion flowers, members of the genus Passiflora, are among the most beautiful and exotic flowers in cultivation. They are rarely grown outside of botanic gardens and arboreta. Species and hybrids of passion flower range in size from less than ½ inch to more than 6 inches in diameter and come in every color (2). Although a couple of selections of passion flower reach the commercial markets in the United States on occasion (usually P. x alto-caerulea or P. vitifolia), many attractive species and hybrids have commercial potential to be marketed in a fashion similar to other tropical vines like Bougainvillea and Mandevilla. Most passion flower hybrids and cultivars are easily grown from cuttings. The limitation to commercial container production of passion flower is controlling the vigorous growth of the vines that can grow a foot or more per week.
There has been limited research on height control in passion flower. Sanderson et al. (1) evaluated several chemicals as foliar sprays and drenches for height control in Passiflora edulis and P. caerulea. They found significant reduction in height with several materials especially ancymidol on P. edulis, but no height control on the more vigorous vines of P. caerulea. Bonzi (Paclobutazol, Uniroyal Chemical Co. Middlebury, CT) can be an effective chemical used to control height in a wide range of container-grown plants. The objective of the current study was to evaluate height control in container-grown passion flowers (all with P. caerulea parentage) using Bonzi as a container drench.
In the summer of 1999, a variety trial with more than 50 species, hybrids and cultivars of passion flower was conducted at the University of Kentucky Arboretum in Lexington. Among the best performers based on plant habit, flower number, and quality were P. `Blue Bouquet' (P. caerulea x P. amythestina), P. `Sapphire' (P. caerulea x P. edulis) and P. x violacea (P. caerulea x P. racemosa). These plants were selected for further evaluation for container production.
In late February, two-node cuttings of each selection were treated with IBA (1,000 ppm in talc) and stuck in Oasis rooting cubes. Cuttings were placed in an intermittent mist bed (5 sec. every 10 min.) with bottom heat (75°C). After two weeks, cuttings were well rooted and moved to 6-inch plastic containers with a peat/bark medium (Scott's 360 Metro mix). Bonzi treatments were applied two weeks after transplanting at 0, 2.5, 5.0, 10.0, 25.0, and 50.0 ppm. Solutions were prepared according to label specifications, and 4 ounces were applied per container. Plants were evaluated after 0, 7, 14, and 21 days for total vine length and number of nodes. Greenhouse conditions were maintained with day/night temperatures of 65/55°F and fertilized with a 100-ppm fertilizer solution (Peter's 20-10-20) at each watering.
Significant height reduction was attained with Bonzi at 25 and 50 ppm, with greatest control at the higher concentration (Table 1). At 21 days after treatment with 50 ppm, there was a 28 and 33% reduction in height for P. `Blue Bouquet' and P. `Sapphire', respectively, compared to untreated plants. Regardless of concentration, no reduction in plant height was observed with P. x violacea (data not shown).
| Table 1. Mean height (cm) of Passiflora 'Blue Bouquet' and P. 'Sapphire' treated with six concentrations of Bonzi evaluated at 0, 7, 14, and 21 days after treatment. | |||||
| Cultivar | Bonzi [ppm] | Days after treatment | |||
| 0 | 7 | 14 | 21 | ||
| 'Blue Bouquet' | 0 | 38a | 60a | 93a | 125a |
| 2.5 | 37a | 55a | 86a | 122a | |
| 5 | 37a | 56a | 87a | 120a | |
| 10 | 40a | 59a | 88a | 122a | |
| 25 | 37a | 55a | 77b | 104b | |
| 50 | 35a | 50b | 68c | 91c | |
| 'Sapphire' | 0 | 20a | 31a | 50a | 69a |
| 2.5 | 19a | 29a | 49a | 70a | |
| 5 | 20a | 28a | 50a | 73a | |
| 10 | 17a | 28a | 47a | 71a | |
| 25 | 19a | 27a | 43b | 60b | |
| 50 | 18a | 26a | 35c | 46c | |
| Means within a column for each cultivar followed by the same letter are not significantly different as determined by Tukey's test at P = 0.05. | |||||
These data are the first to indicate that height reduction can be achieved in passion flower plants derived from P. caerulea. In the study by Sanderson et al. (1), there were no treatments that reduced plant height in P. caerulea. Bonzi was not used in their study, but flurprimidol, which has a similar mode of action to Bonzi (paclobutrazol), failed to impact plant height in P. caerulea at the concentrations tested (2 and 4 ppm). In the current study, similar concentrations of Bonzi also showed no effect on plant height, but concentrations above 25 ppm did reduce plant height in two of the passion flower selections with P. caerulea parentage. However, P. x violacea plants were not affected by concentrations of Bonzi up to 50 ppm.
It should be noted that passion flowers bloom on new growth at each node. For this reason, height reduction as a result of fewer nodes would be undesirable. Bonzi treatment had no affect on the number of nodes produced in any of the passion flower selections (data not shown).
Plants of P. `Blue Bouquet' and P. `Sapphire' showed slight to moderate leaf cupping at all concentrations of Bonzi evaluated. The leaves were not unattractive or necrotic. All plants grew out of the height control and leaf cupping after approximately one month after Bonzi treatment. No floral buds were observed during the 21 days of examination, but all plants initiated flower buds in the month following treatment.
Although 28 and 33% height reduction was significant in this study, plants were still larger than would ideally be desired for greenhouse or nursery production. Perhaps multiple Bonzi treatments possibly at higher concentrations, or Bonzi coupled with cultural practices such as reduced fertilization or pruning, could be used to further reduce plant height. Although not all cultivars were responsive to Bonzi at the rates tested, it does suggest that height reduction is possible and that, when Bonzi is used as a cultural tool, a wide variety of passion flower selections could become profitable nursery plants.
Production and Economics
The North American pawpaw is a temperate member of the mostly tropical Annonaceae or Custard Apple family. Pawpaw has commercial value both as a small landscape tree and as an orchard fruit crop (4). It is also the source of several novel botanical and medicinal extracts (5). Nurseries commonly propagate pawpaw from seed or chip budding. Seed propagation of pawpaw is important to the nursery industry as a source of seedlings for both ornamental and understock production. Currently, chip budding is used to propagate superior fruiting cultivars. One problem with budding is the propensity for pawpaw understocks to sucker and potentially compete with the desired cultivar. Cutting or tissue culture propagation would be a desirable way to establish pawpaw cultivars on their own roots. The objective of our research program in pawpaw is to develop propagation methods for seedling and clonal establishment of plants for commercial production.
Fruits were collected from six sites in Kentucky during the fall of 1996. Seeds were cleaned and combined into one seed lot. Stratification of seeds occurred in rolls of moistened germination paper at 5°C in darkness. At 7-day intervals for 14 weeks, one set of 50 seeds was moved from stratification to germination conditions and germination percentage determined after 14 days.
To determine the pawpaw seeds' ability to withstand drying, 50 fresh seeds were slowly dried at approximately 25°C. At 3-day intervals, seeds were weighed to calculate the approximate change in seed moisture content. Seeds at various moisture contents were stratified for 120 days at 5°C as previously described.
Storage life was determined in seeds extracted from fruits after macerating the pulp and floating off the fruit flesh. Seeds were washed, surface sterilized using a bleach solution, rinsed, and stored in hydrated TerrasorbTM (hydrophilic polymer) at 5°C. Seeds were not permitted to dry out prior to storage. At various times during storage, stratified seeds were surface-sterilized with 10% bleach solution and rinsed three times with sterile deionized water prior to germination testing.
In all germination experiments, seeds were placed in three sheets of germination paper (30 x 38 cm, Anchor Paper Co., St. Paul, MN) moistened with approximately 250 ml of deionized water. Ten seeds were placed between the second and third sheet of rolled paper. Rolls of seeds were placed in 0.5 mil polyethylene bags. Germination was conducted in a 25°C growth chamber in darkness. Fifty to 100 seeds were evaluated per treatment.
Softwood cuttings were taken from either mature or seedling stock plants. Cuttings were stuck in a peat-lite medium and placed under intermittent mist (5 sec every 10 min) with bottom heat 75°F (25°C). Cuttings were treated with a quick dip using IBA at 0, 1000, 5000, or 10000 PPM dissolved in 50% ethanol.
Establishment of tissue cultures was attempted from seedling, mature, or rejuvenated explants. Mature explants were taken from new growth on established, fruiting trees. Rejuvenated explants were from root suckers from mature plants. Tissue culture conditions were MS medium with 5 to 10 
M BA and 1 to 3 M NAA. Photoperiod was 16 hr at 20 mol× sec-1×m-2 of light provided by cool white fluorescent bulbs. Culture room temperature was 25°C.
Pawpaw seeds have a small rudimentary embryo embedded in a large ruminant endosperm (3). A small proportion (12%) of the seed population used in this study germinated after removal from the fruit. The remaining seeds required 8 weeks of chilling stratification to satisfy dormancy (Figure 1). In addition, pawpaw seeds displayed a moderate form of recalcitrance. Seeds lost 50% viability when dried from their initial 37 to 25% moisture. Total loss in viability was between 15 and 5% moisture. There was no significant effect of light on germination. For germination, pawpaw seeds should be stratified for 100 days at 5°C. Seeds stored cold (above freezing) and moist retain good viability for two years (Figure 2).
Figure 1. Germination percentage of pawpaw seeds after stratification at 5°C.
Figure 2. Germination percentage in two seed lots of pawpaw after storage.
Anatomical studies of pawpaw seed revealed a small, linear embryo that does not change in length during cold or warm stratification (2). Cotyledons grew through a specialized channel of cells extending above the cotyledon tips but never emerged from the seed. The time required for the development of the cotyledons delayed seedling emergence more than 50 days. The cotyledons appear to be haustorial and translocate storage material from the endosperm to the growing embryo. Seedling development could be divided into four distinct stages, including radicle protrusion, hypocotyl emergence, epicotyl elongation, and seedcoat abscission.
More than 1,000 softwood cuttings were taken from mature flowering trees throughout the spring and summer. All failed to form adventitious roots. However, seedlings up to 2 months old showed a capacity to root. Cuttings treated with IBA (10,000 ppm) rooted at 75% and averaged two roots per cutting (Figure 3). Seedlings beyond 2 months old lost the capacity to form roots. These data suggest that strategies to revert stock plants to a more juvenile state (like tissue culture or mound layering) will be required before a reliable method for cutting propagation can be obtained.
Figure 3. Root formation in seedling cuttings treated with 10,000 ppm IBA.
The effect of juvenility on explant performance was seen with the inability of explants from 26 mature sources to respond in culture. Of the 551 mature explants, 72% were successfully disinfested, but only 4% survived in the culture environment (1). Most of the mature explants turned black and lost tissue integrity. The explants that were alive did not respond in culture and produce axillary shoots or adventitious buds. Only the small percentage of explants from mature sources that survived showed some tissue proliferation after approximately 7 months in culture.
In contrast, 88% of seedling explants showed expanded shoots (> 3 cm) and were suitable for subculture after 6 weeks (Figure 4). For explants from root suckers, axillary shoot elongation began in 42% of the explants after eight weeks. Although explants from root suckers did not respond as rapidly or at the high percentages of the seedling explants, these explants did respond in culture and would produce clones of the donor plant.
Figure 4. Shoot formation from seedling and rejuvenated explants of pawpaw.
Production and Economics
Bottlebrush Buckeyes are under investigation for rootability in a layering propagation system. Forty plants were planted during 1995 and were mistakenly bushhogged during the fall of 1998. Many new stems arose from each initial plant. During the summer of 2000, the plant rows were mounded to a depth of 18 inches with aged sawdust. The rows are on drip irrigation with daily application.
Each month 10 random plants are being chosen for propagation. Three branches are selected on each plant. The sawdust is removed to within an inch or two of the ground. A lateral slit about 1 inch long is cut about halfway through the branch. No. 3 Hormex rooting hormone is introduced into the slit. The branch is then re-covered with sawdust. Plants will be treated monthly for nine months over a period of one year. During the months of December, January, and February, no treatments will be made because of weather. Initial response after 60 days is that rooting is occurring at the point of treatment. More information will be available after the year-long cycle is complete.
Pest Management—Insects
According to the U.S. Department of Agriculture (USDA), we are facing an "impending pollination crisis." Both wild and managed pollinators are disappearing at alarming rates, due to habitat loss, pesticides, and parasites such as tracheal mites. As one of the objectives aimed at solving this problem, the USDA and other concerned scientists have highlighted the importance of evaluating the potential hazards of certain insecticides that are applied in areas frequented by pollinators. Such sites include nurseries and landscapes in which flowering plants or weeds are grown.
Merit (imidacloprid) is a persistent, systemic insecticide that is widely used to control pests of woody and herbaceous ornamentals, as well as white grubs in turf. Because imidacloprid is inherently toxic to bees, it could potentially harm pollinators if translocated to the nectar or pollen of flowering ornamentals in plant beds or within flowering weeds between nursery rows. The same exposure is important for nectar-producing plants sold for butterfly gardening. However, hazards of an insecticide to a nontarget organism are determined by degree of exposure, as well as inherent toxicity of the pesticide. We investigated the possible nontarget effects of imidacloprid on bumblebees that foraged on flowering clover in turf.
Fifteen field plots containing flowering white clover were grouped by initial clover density in five replicates. A pair of plots were sprayed with the wettable powder formulation of imidacloprid, one receiving post-treatment irrigation and the other not. A third plot was left untreated without irrigation as the control. After treatment, field cages were placed over each plot, and a commercially acquired hive of bumblebees was placed into each. Bumblebee foraging was monitored daily for 28 days after treatment. At the end of that period the hives were collected and frozen. Each hive was dissected, and hive health was measured by comparing the weight of the hive, the total bee biomass, and the queen. Also the numbers of brood chambers, adult workers, and honey pots were counted. Experiments regarding the hazards imidacloprid poses to butterflies are still in progress.
Wettable powder applications of imidacloprid that were not irrigated into the soil had an adverse effect on hive health. The numbers of brood chambers, workers, and honey pots, as well as the worker biomass and hive weights, were significantly reduced on nonirrigated imidacloprid treated plots relative to control plots. However, there were no differences between those treated plots receiving post-treatment irrigation and control plots. This work suggests that following applications of imidacloprid with irrigation will greatly reduce the exposure to the bumblebees. Moreover, the rate at which imidacloprid is translocated to either the nectar or pollen of a flowering plant is in too low a concentration to have any toxic effects.
Understanding ways to better reduce the hazards of pesticides to pollinators lends itself to more environmentally friendly management practices in nurseries. This work indicates that bumblebees that feed on the nectar or pollen of an imidacloprid-treated plant are at a lesser risk of insecticide poisoning if treatments are followed with adequate irrigation. These data reiterate the need for post-treatment irrigation, not only for increased efficacy against grubs but also for reducing exposure to pollinators. This knowledge helps protect a useful tool for nursery pest control against potential claims of post-treatment pollinator poisoning.
| Table 1. Mean comparisons between irrigated and nonirrigated imidacloprid-treated plots and control plots. | ||||||
| Control | Irrigated | Nonirrigated | F-stat | P-value | ||
| Weight (g) | hive | 86.44 ± 13.72 | 80.61 ± 5.29 | 39.60 ± 26.80 | 11.81 | 0.0041 |
| workers | 7.22 ± 2.02 | 7.97 ± 0.86 | 3.25 ± 1.30 | 18.63 | 0.0010 | |
| queen | 0.71± 0.09 | 0.70 ± 0.13 | 0.70 ± 0.06 | 0 | 0.9995 | |
| Numbers | adults | 55.40 ± 14.04 | 48.60 ± 8.76 | 21.80 ± 4.71 | 13.23 | 0.0029 |
| brood chambers | 28.60 ± 8.53 | 25.00 ± 7.35 | 3.60 ± 1.52 | 18.65 | 0.0010 | |
| honey pots | 24.00 ± 5.87 | 24.20 ± 9.55 | 6.80 ± 9.42 | 6.37 | 0.0222 | |
| dead bees | 0.0 ± 0.0 | 1.00 ± 1.41 | 13.20 ± 4.71 | 15.52 | 0.0018 | |
Pest Management—Insects
Since its accidental introduction around 1916, the Japanese beetle, Popillia japonica Newman, has become the most destructive pest of landscape plants in the eastern United States. The adults feed on about 300 plant species in 79 families, including woody ornamentals, herbaceous perennials, and field and garden crops with annual control costs amounting to hundreds of millions of dollars.
Associational resistance occurs when a plant is protected from herbivory through being associated with (e.g., growing near) other plant species that may produce masking or repellent odors that interfere with a pest's host location behaviors. For example, potato beetles, which orient upwind to the odor of solanaceous plants, are repelled by some non-host plants. Perhaps the most familiar application of this concept is companion planting in gardens.
Osage orange is a native species with a long history of economic use and a rich folklore concerning its alleged pharmacological properties. The fruits, or hedge apples, contain natural compounds that prevent spoilage and are reportedly toxic to herbivores. Also, the fruits are allegedly repellent to cockroaches and other household pests. Ginkgo, a deciduous gymnosperm native to eastern China, is notably resistant to diseases and insect pests, including the Japanese beetle. The fruits, which are actually tan, plum-like, naked seeds, have a fleshy covering that is distinctively pungent. Hedge apples and ginkgo seeds are both present in July, during peak flight activity of adult Japanese beetles. Red cedar (Juniperus spp.) shavings, commonly sold as animal bedding to control animal odors, are alleged to be nontoxic repellents for German cockroaches and fleas. There have been few evaluations of the use of cedar volatiles against insect pests that do not readily feed on cedar.
Our objective was to evaluate whether the volatiles from ginkgo and hedge apple fruit or from cedar shavings could protect flowers and leaves of roses and perennial hibiscus from attack by Japanese beetles. On 19 July, fresh hedge apples and ginkgo fruit were collected by hand from plantings around Lexington. Cedar shavings used for animal bedding (Premiere Pet™ Aromatic Red Cedar shavings) were purchased. In the laboratory, an average weight of a single hedge apple fruit was calculated and then an equivalent mass of cedar and ginkgo was determined to standardize each treatment by weight. In an attempt to simulate bruising and increase volatility, the fruit treatments were placed in a -20°C freezer for 2 hours before beginning the test. All treatments were placed separately in nylon mesh bags as follows: 1 hedge apple fruit per bag; 4 ginkgo fruit per bag, and approximately 430 g of cedar shavings per bag.
On 20 July, we placed potted flowering rose, Rosa `Ultimate Pink', and rose mallow, Hibiscus moscheutos `Hinpink' plants on the old driving range at the University Club of Kentucky (Lexington), an area with a high population of Japanese beetles. Plants were placed parallel to the prevailing winds and spaced about 1.5 m apart to reduce interactions among treatments. To ensure similarity among plants in a replicate, the plants were graded by number of open blooms and then assigned to the replicates. Four separate areas of the driving range were used, one for each replicate. Each plant was bordered by four plastic fenceposts set at cardinal directions. Each plant received four total bags of each treatment, one per post. Bags for a particular treatment were tied to the posts at bloom height. Empty nylon bags were tied at bloom height to posts that were surrounding control plants. Each treatment was replicated in four separate locations on roses and only three locations for the hibiscus treatments.
During the afternoon and evening of 20 July, the number of Japanese beetles on each plant was counted by a single observer. Additional counts were made during the morning and afternoon of 21 July, with the final count in the morning on 24 July.
Although beetles were present on most of the rose plants, there were not enough beetles for comparison on hibiscus plants at any observation period. Therefore, only data from the rose evaluations are presented. Roses bordered by hedge apples had significantly more beetles than control rose plants during all observation periods except for 6 p.m. on 20 July (see Figure 1). Plants bordered by cedar shavings also had high numbers of beetles. After only one day in the field, those plants with cedar shavings were not significantly different from those with hedge apples. However, plants with cedar were only significantly different from controls during the last two observations. Plants bordered with ginkgo fruit were never significantly different from control plants.
Figure 1. Number of beetles present over time on blooming rose plants surrounded either by fruit of ginkgo or hedge apples, or by cedar shavings.
The rose plants bordered by hedge apple and cedar also had the most foliar and floral damage at the end of the study. Across all four replicates, the rose plants bordered by cedar had 1 to 15% defoliation, and two of the four plants had no blooms. Similarly, the roses bordered by hedge apples had 5 to 15% defoliation with no intact blooms on any plant. The control and ginkgo-bordered roses had little to no defoliation or flower feeding.
Past work has demonstrated that Japanese beetles exploit feeding-induced plant volatiles as kairomones, which accounts for aggregative behavior within trees. In addition, blend complexity generally increases beetle response. Therefore, the increased attraction to the cedar and the hedge apple may be a response to an increase in the complexity of the volatile blend. The increased beetle number over time is typical of the response of the beetles recorded in other studies where beetles respond to kairomones produced by plants with fresh beetle damage.
The use of non-host odors to mask or repel insects has been used for some pests as an exclusionary control method. Our objective was to identify potential non-host odors that would protect susceptible plants from attack by the Japanese beetle. However, we found that the use of non-host fruit or plant parts increased the number of beetles recruited and the overall damage of roses that were to be protected. This study suggests that the use of masking odors may not be a viable means of protecting plants and may even increase a plant's susceptibility to Japanese beetles.
Pest Management—Insects
Tiphia wasps are the dominant group of parasitic insects that attack white grubs. This wasp burrows into the soil, where it locates a host grub. The wasp then stings the grub and attaches an egg. Upon hatching, the wasp larva consumes the host grub and then spins a cocoon in the soil where it will overwinter and emerge the next year as an adult. In certain areas, up to 60% of the white grub population may be parasitized, while in other areas, very little parasitism occurs. Little work has been done on the biology and conservation of these wasps. The focus of our research is to study the biology of Tiphia wasps and then apply this information to conserve and increase the benefits received from these wasps.
During 2000, we determined that two species of Tiphia are common on golf courses in Kentucky. Adults of Tiphia vernalis, a species introduced for control of Japanese beetles, were active from May 4 to June 1. Tiphia pygidialis, a native species that attacks masked chafer grubs, were active from August 1 to September 14. Yellow pan traps were effective for monitoring early-season activity of T. vernalis, whereas both species could be monitored by spraying a 10% sugar water solution on the turf. Weekly sampling of the natural grub population showed that both Tiphia species parasitized primarily third instars. Parasitism of masked chafers averaged 15% at two golf courses but was as high as 37% at some sites.
Cues used by Tiphia to locate grubs below ground were examined by use of an "ant farm," positioned horizontally to allow observation of wasp behavior in the soil. Wasps were found to locate their victims by following species-specific scent trails left by the grub as it moves through the soil. Wasps showed an even stronger response to frass from their host grubs. This is the first study to show how Tiphia wasps locate grubs underground. Ovipositional behavior of each wasp species was also characterized. Both T. vernalis and T. pygidialis deliver a paralyzing sting and then manipulate the body of the grub in preparation for oviposition. Then, the female laboriously scrapes the grub to thin the cuticle where the egg will be laid. T. vernalis lays its egg on the underside of the grub, whereas T. pygidialis lays its egg on the back of the host grub. Eggs hatch in 3 to 5 days. Larval development is completed in about 21 days, after which a cocoon is spun. No-choice tests were conducted with several grub species to study the range of grubs that each wasp will attack. When offered Japanese beetle, masked chafer, or May beetle grubs, T. vernalis parasitized only Japanese beetles. Tiphia pygidialis were tested with the aforementioned grub species, plus two additional exotic species, European chafer and Oriental beetle. In general, only masked chafer grubs were attacked. In one case, however, T. pygidialis parasitized and completed larval development on a third-instar European chafer.
The relationship between the developing larval Tiphia and its host grub was examined in the lab. Shortly after being parasitized, grubs quit feeding on grass roots and will move down into the soil profile to depths as much as 20 cm. We speculate that Tiphia wasps manipulate juvenile hormone levels in parasitized grubs, causing them to prematurely descend. Hemolymph was collected from normal and parasitized grubs to test this hypothesis. Our experiments show that once parasitized, grubs may no longer contribute to turf damage. Persons monitoring for the presence of parasitized grubs should look deeper in the soil where parasitized grubs will be found.
Dilute sugar water sprays were applied to turf in an attempt to attract Tiphia wasps and increase parasitism of grubs. Although large numbers of wasps were observed feeding on the sprayed grass blades, no grubs were parasitized in the sprayed turf. In the surrounding, unsprayed turf, however, up to 37% of the grub population was parasitized. This indicates that sugar sprays applied near, but not directly on, grub-infested turf may increase the rate of parasitism. Floral resources have been shown to enhance performance of parasitoids; therefore, 20 species of flowering perennials were planted and monitored to determine if they attract Tiphia wasps. No wasps were found on these plantings. Since sugar water sprays did not attract any wasps when applied around these floral resources, it is believed that no wasps were present in this area.
We will continue to study the basic biology of these two wasp species in 2001. Additional tests will be conducted to determine if planting of wildflowers, use of sugar sprays, or other tactics can increase parasitism by Tiphia. Studies on the impact of turfgrass insecticides, including newer chemistries, on the performance of these wasps will be undertaken. Such information, together with our studies of the wasps' seasonal activity, will increase awareness of the benefits of Tiphia wasps in golf-course IPM programs.
Pest Management—Diseases
Plant disease diagnosis is an ongoing educational and research activity of the UK Department of Plant Pathology. We maintain two branches of the Plant Disease Diagnostic Laboratory, one on the UK campus in Lexington, and one at the UK Research and Education Center in Princeton. Of the more than 4,000 plant specimens examined annually, about 40% are landscape plant specimens (1).
Making a diagnosis involves a great deal of research into the possible causes of the plant problem. Most visual diagnoses involve microscopy to determine what plant parts are affected and to identify the microbe involved. In addition, many specimens require special tests such as moist chamber incubation, culturing, enzyme-linked immunosorbent assay (ELISA), electron microscopy, nematode extraction, or soil pH and soluble salts tests. Computer-based laboratory records are maintained to provide information used for conducting plant disease surveys, identifying new disease outbreaks, and formulating educational programs.
After the hot and dry 1999 growing season and a relatively mild winter, the 2000 growing season in Kentucky reverted to near-normal precipitation and temperature levels. Although soil moisture levels were still short from the previous drought, normal to above-normal rain in spring and early summer eased the drought. Indeed, July was characterized by below-normal temperatures and above-normal rainfall. This trend continued into the late summer in eastern Kentucky regions, but hot, dry weather returned in the western parts of the state.
Thus, with mostly normal rainfall, much of the 2000 growing season was favorable for foliar diseases of landscape plants. Drought still influenced plant health, however, because some vascular wilts, canker diseases, and tip blights began the year before during the drought stress.
Deciduous tree diseases. Above-normal rainfall in April got foliar diseases off to a good start. Cedar rust (Gymnosporangium juniperi-virginianae, G. clavipes, G. globosum) infections were widespread. Rust-susceptible crabapple leaves showed significant cedar-apple rust spots, and hawthorn fruits and shoots were heavily infected with cedar-quince rust. Flowering crabapple scab (Venturia inaequalis) was very active, and most susceptible flowering crabapples were defoliated from scab by mid-summer. The maple, dogwood, ash, and sycamore anthracnose fungi (Kabatiella, Discula, and Apiognomonia) were also very active because of the early wetness. Dogwood anthracnose was confirmed from Harrison County for the first time. An apparently new anthracnose disease of yellowwood was found on trees in several Kentucky landscapes. Sourwood leaf spot (Cercospora oxydendri) was serious in some locations. Dogwood powdery mildew (Microsphaera, Phyllactinia spp.), a disease which has become important in recent years, was fairly serious in many landscapes. Crabapple powdery mildew (Podosphaera leucotricha) was widely evident. Bacterial leaf scorch (Xylella fastidiosa) was easily detected visually on red and pin oaks in late summer. Drought stress the previous season appeared to have made this disease much worse. Previously infected trees seemed to show accelerated rates of decline. In addition to branch dieback, increased numbers of large, mature pin oaks in most Kentucky urban areas are dying from bacterial leaf scorch. Bacterial leaf scorch was also diagnosed in sugar maple and London plane. Botryosphaeria canker (Botryosphaeria dothidea) of various woody plants and Hypoxylon canker (Hypoxylon atropunctatum) of oak, probably exacerbated by the previous year's drought, were more noticed. Verticillium wilt (Verticillium dahliae) appeared on maple, redbud, smoke-tree, and magnolia; in the latter case, symptoms were visible in previous years' wood on young, recently planted trees. Ash yellows, a phytoplasma-caused disease, was more observable in landscapes this year.
Needle evergreen tree diseases. Maturing Austrian and Scots pines continue to die from tip blight (Sphaeropsis sapinea) and pine wilt nematode (Bursaphelenchus xylophilus). The drought of the previous year seemed to exacerbate these diseases. Although the drought occurred in summer last year, many needle evergreens such as pines and spruces retained their foliage and did not turn brown and die until winter or spring this year. White pine decline (linked to high pH, compacted soils with high clay content, or with root disturbance) continues to take its toll.
Shrub diseases. Black root rot (Thielaviopsis basicola) of holly, inkberry, Japanese holly, and boxwood remains a problem. In addition to the usual outbreaks of black spot (Diplocarpon rosae) and powdery mildew (Sphaerotheca pannosa), roses this year had additional problems with rose mosaic virus and with the devastating rose rosette disease.
Perennial and annual plant diseases. Black root rot (Thielaviopsis basicola) of annuals such as petunia, lavender, and pansy was a problem in many flower beds in spring and again in fall. Southern blight (Sclerotium rolfsii) was more commonly observed this year on hosta, phlox, and echinacea. Stem rot (Rhizoctonia solani) also affected many landscape flowers, especially impatiens, vinca, lily, and petunia. Peony, especially tree peony, was afflicted with leaf spot and blight (Cladosporium paeoniae) and iris with leaf spot (Heterosporium iridis). Bacterial blights (Pseudomonas and Xanthomonas spp.) were observed on chrysanthemum, impatiens, geranium, and several other flowers. Poinsettia scab (Sphaceloma poinsettiae) outbreaks were noted.
Landscape lawn diseases. The usual spectrum of turfgrass diseases appeared throughout the growing season. Perennial ryegrass gray leaf spot (Pyricularia grisea) was fairly serious this year.
The first step in appropriate pest management in the landscape is an accurate diagnosis of the problem. The UK Plant Disease Diagnostic Laboratory assists the landscape industry of Kentucky in this effort. To serve their clients effectively, landscape industry professionals, such as arborists, nursery operators, and landscape installation and maintenance organizations need to be aware of recent plant disease history and the implications for landscape maintenance. This report provides useful information for landscape professionals.
Pest Management—Diseases
Sphaeropsis tip blight (formerly known as Diplodia tip blight) is a common, worldwide disease of more than 30 pine species and other conifers. Newly infected shoots stop growing and quickly die. Typical symptoms of Sphaeropsis sapinea infection include stunted shoots with necrotic, stunted needles, resinous cankers, and a general decline of the tree (1). In Kentucky, the disease is severe enough that trees infected for several successive years are often removed from the landscape long before they become mature (80 years in their native environment) (2). A survey was made in the region to determine if the pathogen is present in asymptomatic shoots and needles of Austrian and Scots Pine. Asymptomatic shoots were tested from diseased trees and from asymptomatic, apparently healthy trees.
Diseased and asymptomatic shoots were collected from diseased and healthy trees growing mainly in Kentucky, but also from Illinois, Indiana, and Ohio. Pine tissues were surface disinfested and plated onto acidified potato dextrose agar using standard fungal isolation techniques. Sphaeropsis isolations were confirmed by subculturing the fungus on water agar with sterilized pine needles and observing development of pycnidia on these needles. For sample collections made locally, the fungus was also isolated from different surface-disinfested tissues dissected from asymptomatic Austrian pine shoots. Fungal isolates were tested for pathogenicity on 3-year-old Austrian pines in the greenhouse.
Asymptomatic Austrian and Scots pines were frequently latently infected with S. sapinea (Table 1). The pathogen could be recovered from all parts of asymptomatic shoots, including needles; stems; buds; first-, second-, and third-year cones (not asymptomatic); and male flowers. Latent infections were localized in the outermost tissues of the shoots and branches (Figure 1).
Figure 1. Current year shoot tissues where S. sapinea could be recovered from diseased Austrian pines.
S. sapinea isolates from latently infected tissues of Austrian and Scots pines were pathogenic. Fungal isolates derived from either diseased or asymptomatic tissue caused typical tip blight symptoms within two weeks of inoculation; 74% of inoculated trees showed symptoms while the control trees remained healthy throughout. The causal fungus was recovered from all diseased tissue. Of the 26% of inoculated trees which failed to show symptoms, 10 trees were sacrificed for isolations and from nine of the 10, S. sapinea was recovered from needles and stem tissue at least 5 cm beyond the point of inoculation. These latently infected trees represented fungal isolates from both latent and outwardly diseased samples.
In summary, the results of this work show that:
From: Flowers, J.L., et al., APS Annual Meeting poster presentation, Aug. 2000.
Information on Austrian pine tip blight identification, disease progress, and prognosis made in Lexington can be extended to Austrian pines in other regions of the state. This knowledge may assist landscape architects and managers in deciding whether to use Austrian pine in the landscape. Indeed, for longevity and ease of maintenance, Austrian pines may not be a good choice for Kentucky landscapes. The finding that the fungus already exists in the tree or parts of the tree before symptoms develop will have an enormous impact on tip blight disease management decisions, should the work be expanded.
| Table 1. Isolation of S. sapinea from diseased and asymptomatic Austrian and Scots pines. | ||||||||
| Tree species and health | Number of shoots sampled | Percent recovery of Sphaeropsis sapinea from: | ||||||
| Trees | Diseased shoots | Asymptomatic shoots | ||||||
| Previous year's stem | Current year's shoot | Previous year's stem | Current year's shoot | |||||
| Diseased | Asymptomatic | |||||||
| Asymptomatic Austrian pine | 0 | 68 | 17 | - | - | 8 | 4 | |
| Diseased Austrian pine | 46 | 97 | 100 | 87 | 100 | 73 | 70 | |
| Asymptomatic Scots pine | 0 | 28 | 17 | - | - | 4 | 30 | |
| Diseased Scots pine | 33 | 36 | 100 | 82 | 100 | 42 | 80 | |
Pest Management—Diseases
Tip blight disease, caused by the fungus Sphaeropsis sapinea, is a major problem of Austrian pine (Pinus nigra) in the landscape (1). Control by pruning or spraying is difficult and usually ineffective; most affected trees eventually die or are removed (2). Young trees that are not yet producing cones are rarely affected by tip blight. It has been suggested that a primary source of inoculum may be old infected cones and that young trees escape due to lack of locally produced infective propagules. However, we have found that the tip blight fungus is present in healthy parts of trees (found in more than 70% of symptomless twigs), or in healthy young trees (17%), living as a latent pathogen or possibly as an endophyte within the twigs (3,4). This study is intended to determine whether fungicide injection can prevent new infections and further spread of tip blight disease. We hope to determine also whether injection of pines with fungicides can eradicate S. sapinea from within infected/infested pines and the impact of fungal eradication on disease.
Two distinct groups of Austrian pines on the UK campus were selected for injection treatments as described below: Experiment 1, mature diseased (1 to 50% tip blight) Austrian pines (six replicates) and Experiment 2, maturing, mostly non-diseased Austrian pines (10 replicates). Disease symptoms were evaluated in mid- to late summer each year by estimating the percent of diseased shoot tips per tree. Diseased branches previously removed for sanitation purposes were included in the estimate. During July 2000, shoot and needle samples (two each) from asymptomatic and diseased shoots were collected from each treated tree and the pathogen cultured on acidified PDA using standard microbiological techniques. The fungal cultures were identified and confirmed microscopically following inoculation of autoclaved pine needles.
Experiment 1. Sixteen 22-year-old diseased Austrian pines located on traffic islands on the UK campus received one of four treatments. Treatments, arranged in a randomized complete block design and replicated on four individual trees, consisted of injections at labeled rates of a) oxycarboxin (Carboject), b) debacarb (Fungisol), c) tebuconazole (Tebuject), and d) water used as controls. Treatments were made 8 May 1999 (capsules removed 12 May; water controls injected 18-22 May), when the candles of the pines were partly elongated, and again 6-9 May 2000 (capsules removed 16 May), with future injections to be made in spring 2001. Due to the demise of several of the traffic-island trees in the first year, eight additional 20-year-old trees located around the perimeter of a UK campus parking lot nearby were injected in May 2000. Trees have been grouped into randomized complete blocks, and each treatment is now replicated five or six times with each replicate being an individual tree.
Experiment 2. From a group of 71 mostly disease-free 13- to 14-year-old Austrian pines forming a screen planting on the UK campus, 40 trees were injected in 1999 and again in 2000 as described above. The experiment was designed as a randomized complete block experiment with 10 replicates.
Experiment 1. Disease levels in the mature trees were quite variable (1 to 50%) when treatments were initiated in 1999. In addition, 1999 was a year of extreme drought with watering restrictions placed on Lexington residents and the UK campus. By mid-summer, when disease ratings were made, disease levels were much higher. Drought stress caused several of the severely diseased trees in the experiment to die. Consequently, another group of less diseased trees were added to the experiment in 2000, but they have gone through only one injection treatment. Thus, it is difficult to assess the effects of two years of fungicide injections on disease levels in this group of trees (Table 1). There were no significant differences in recovery of the pathogen from diseased or healthy shoots of the trees in this experiment (Table 2). During the injection process, it was noticed that some of the capsules soon filled with pitch from the tree. Thus, it is difficult to know whether all capsules were actually emptied into the injection site.
| Table 1. Summer 1999 and 2000 disease ratings (percent blighted shoot tips) for Experiment 1, mature diseased (1 to 95% tip blight) Austrian pines (six replicates) and for Experiment 2, maturing, mostly non-diseased (less than 1% tip blight) Austrian pines (10 replicates). | ||||||||
| UK Austrian pines | Experiment 1 trees | Experiment 2 trees | ||||||
| Treatment | Rating year | Range | Average * | Average for original trees | Original trees' disease percent in 2000 vs. 1999 | Range | ||
| 1 - Fungisol | 1999 | 1-85 | 28 | 08 | 0 | |||
| 2000 | 1-25 | 07 | 10 | 125 | 0 - <1 | |||
| 2 - Tebuject | 1999 | 1-90 | 51 | 38 | 0 | |||
| 2000 | 1-95 | 28 | 49 | 129 | 0 - <1 | |||
| 3 - Carboject | 1999 | 9-52 | 34 | 34 | 0 | |||
| 2000 | 5-70 | 31 | 49 | 144 | 0 - <1 | |||
| 4 - Water | 1999 | 23-35 | 29 | 29 | 0 | |||
| 2000 | 5-60 | 33 | 46 | 159 | 0 - <1 | |||
| * Percent disease changed substantially from year to year if one heavily diseased tree died or if new, less diseased trees were added after the first year. | ||||||||
| Table 2. Isolation of Sphaeropsis sapinea from UK campus pines: Experiment 1, mature diseased (1 to 95% tip blight) Austrian pines (six replicates). Experiment 2, maturing, mostly non-diseased (less than 1% tip blight) Austrian pines (10 replicates) treated with fungicides via trunk injections. Percent needles and shoots yielding S. sapinea in culture (four samples per tree). | |||||
| UK Austrian pines | Experiment 1 trees | Experiment 2 trees | |||
| Treatment and sample health status | Percent recovery of S. sapinea | Percent recovery of S. sapinea | Proportion of trees with S. sapinea | ||
| 1 - Fungisol, symptomless shoot | 55.0 a * | 7.5 a | (1:10) | ||
| 3 - Tebuject, symptomless shoot | 40.0 a | 17.5 a | (5:10) | ||
| 7 - Water, symptomless shoot | 66.7 a | 22.5 a | (5:10) | ||
| 5 - Carboject, symptomless shoot | 45.8 a | 25.0 a | (7:10) | ||
| 4 - Tebuject, diseased shoot | 75.0 a | 68.8 b | (8:8) | ||
| 8 - Water, diseased shoot | 79.2 a | 75.0 bc | (6:6) | ||
| 2 - Fungisol, diseased shoot | 80.0 a | 79.2 bc | (6:6) | ||
| 6 - Carboject, diseased shoot | 66.7 a | 87.5 c | (6:6) | ||
| * Means in a column followed by the same letter are not significantly different; Waller-Duncan K-ratio t-test (K = 100, p = 0.05). Fungisol = debacarb Carboject = oxycarboxin Tebuject = tebuconazole | |||||
Experiment 2. The younger, minimally diseased trees showed very little evidence of disease (Table 1), but the potential for future disease development is present because an occasional diseased shoot was found and harvested for fungal isolations. These diseased shoots yielded significantly higher levels of the pathogen in culture than did asymptomatic shoots from the same trees. S. sapinea was isolated from all trees with a diseased shoot, whereas the fungus was isolated from only one in 10 asymptomatic shoots of Fungisol-treated trees compared with five of 10 water- or Tebuject-treated and seven of 10 Carboject-treated trees. Injections will be made again in spring 2001, so there will be an opportunity next summer to see if this trend continues.
Information on injections as a management tool for Austrian pine tip blight may provide insights on the biology of the fungus and its host and potential control of the disease. This knowledge may assist landscape architects and managers in deciding whether to use Austrian pine in the landscape. Indeed, unless efficient control measures are developed, for longevity and ease of maintenance, Austrian pines may not be a good choice for Kentucky landscapes. If treatments can eradicate the fungus that already exists in the tree or parts of the tree before symptoms develop, this information will have an enormous impact on tip blight disease management.
Pest Management—Diseases
Heritage fungicide (azoxystrobin), one of a new class of fungicides known as strobilurins, has many registrations for ornamental crops. Another form of azoxystrobin, called Abound, is used in the fruit industry, but is not recommended for apples because of phytotoxicity to the variety McIntosh and to apples genetically related to McIntosh. The effect is so pronounced that grape growers using azoxystrobin are warned not to use the fungicide if they also grow apples (1). This research was done to determine if a selection of flowering crabapples would be similarly affected.
This trial was conducted on a planting of fully mature flowering crabapple (Malus spp.) cultivars established in 1992 on the UK Agricultural Research Fa000 UK Nursery and Land Plots are located on a fertile, well-drained Maury silt loam soil. The trees were arranged in a randomized complete block design with five replications. For this experiment, half-trees received treatment while the other half of each tree remained untreated. Trees in replicates 1, 3, and 5 were treated on their north side while trees in replicates 2 and 4 were treated on their south side. Treated parts of all trees were sprayed with the fungicide Heritage (8.0 oz/100 gal) to run-off using a Solo hand-pumped backpack sprayer. Four applications were made on April 26, May 9 and 24, and June 7 at two-week intervals beginning at bloom. These dates coincide with normal times of fungicide application for control of scab, powdery mildew, and rust diseases. Eastern tent caterpillar infestations were noticed in the plots and webbed "nests" were removed from the trees and destroyed. Crabapples were watched for fungicide reactions during May and June and evaluated for their reaction to the fungicide treatment on July 27 by examining all leaves for appearance and color on at least 10 shoots on each half of each tree.
Sprays were applied in a timely way, and typical Lexington, Kentucky, weather with favorable rainfall prevailed throughout the trial. Not all cultivars were fully replicated because this was a fairly old planting, and several of the trees had been destroyed due to mower damage or drought stress from previous years. In any case, none of the crabapple cultivars in the experiment showed any symptoms of phytotoxicity resulting from treatments with Heritage. The 25 cultivars used in this test (numbers of trees in parentheses) are: Adirondack (2), Beverly (1), Brandywine (1), Candymint `Sargent' (3), Centurion (4), Coralburst (2), David (3), Dolgo (3), Doubloons (2), Edna Mullins (2), Floribunda (3), Harvest Gold (5), Indian Summer (2), Jewelberry (2), Malus baccata `Jackii' (1), Naragansett (3), Pink Princess (3), Purple Prince (2), Radiant (1), Red Splendor (4), Sinai Fire (1), Snow Magic (3), Tina (2), Velvet Pillar (3), Zumi `Winter Gem' (2).
Although many more flowering crabapples need to be tested, landscape managers, arborists, and nursery operators may rest a little easier when Heritage sprays are applied nearby to nursery blocks with crabapples or when their sprayer is contaminated with Heritage.
Pest Management—Diseases
The experiment was established to compare the efficacy of different rates of the fungicide Lynx with standard fungicides for control of cedar-quince (Gymnosporangium clavipes) and cedar-hawthorn (G. globosum) rust of hawthorn (Crateagus laevigata). Cedar-quince rust was the main target because it normally is more prevalent and damaging in landscape hawthorns (1); a prominent indicator of cedar-quince rust is numbers of flower (fruit) infections, but it can also cause twig cankers. Cedar-hawthorn rust causes leaf spots on hawthorns. Plots were established on mature hawthorn trees growing in landscape beds on the University of Kentucky campus. Treatments were applied to trees experimentally grouped in a randomized complete block design and replicated four times as single tree replicates. Treatments were applied with a Solo hand-pumped backpack sprayer. Spray applications were made March 26 (tree phenology_green tip to tight flower cluster), April 9 (tight flower cluster to open flower cluster), April 23 ("popcorn" flowers to full bloom), and May 7 (flower petal fall, leaves fully expanded). These applications coincided with fungal telia production on cedars (junipers).
Rust spores were abundant on nearby cedar trees, and weather was generally favorable for several infection periods to occur during the weeks of fungicide application. The major indicator of infections actually occurring, however, are infected flowers and fruit, and due to a drought in 1999, there were few flowers produced in 2000. Thus, due to a lack of flowers, fruit infection levels were extremely low, much lower than normal. Leaf infections were at their normal and twig cankers were infrequent. Evaluations of fruit (cedar-quince rust) and leaf (cedar-hawthorn rust) infection levels were made July 27. Most trees had few fruit and some had none, but where there were fruit, up to 200 fruit were examined, and the number of infected fruits was recorded. Similarly, 500 to 1000 leaves were examined per tree, and the number of infected leaves was recorded. Fruit and leaf infection levels on water-treated trees (check) were only 4.25 and 1.05%, respectively. Although infection levels were low, all fungicide treatments provided significant control of rust on hawthorn (Table 1).
During wet spring weather, cedar rusts are very infective and by late summer can cause significant damage to susceptible hawthorn shoots and twigs. Fungicides provide landscape managers, arborists, and nursery operators an additional tool for managing cedar-rust diseases.
| Table 1. Effect of fungicides on cedar rusts of hawthorn. | ||
| Treatment and rate/100 gal. | Percent fruit infection | Percent leaf infection |
| Lynx, 3.3 oz | 0.000 a * | 0.000 a |
| Lynx, 4.4 oz | 0.000 a | 0.000 a |
| Banner MAXX, 5.0 oz | 0.000 a | 0.025 a |
| Lynx, 2.2 oz | 0.167 a | 0.000 a |
| Heritage, 4.0 oz | 1.043 ab | 0.200 a |
| Water check | 4.250 b | 1.050 b |
| * Means in a column followed by the same letter are not significantly different, Waller-Duncan K-ratio t-test (K = 100, P = 0.05). | ||
Pest Management—Diseases
Powdery mildew is increasingly becoming a problem in Kentucky landscapes (1). There are several effective fungicides available for use in nurseries and landscapes; there are some promising biological control materials becoming available as well.
This test was conducted at the University of Kentucky Horticultural Research Farm and was designed to test the efficacy of MT-2000, a biocontrol fungicide, at different application regimens in comparison to standard treatments for control of dogwood powdery mildew (Microsphaera sp.). Four-year-old dogwood (Cornus florida) seedlings were grown in 3-gallon pots containing Barky Beaver nursery potting mix. The plants were placed in a shade structure and were watered as needed with automatic overhead sprinklers. Dogwoods were fertilized with 9 g of 14-14-14 fertilizer/pot on June 19. Fungicides were prepared in small quantities and were applied using a hand-held atomizer/sprayer. Treatments were replicated five times, and treated plants were arranged in a completely randomized design. Most treatments were initiated on June 2; however, weekly treatments of the biocontrol fungicide MT 2000 did not begin until June 30. Fungicide rates and application dates are presented in Table 1. Percent powdery mildew incidence and severity were recorded August 29. Incidence was recorded for presence of both signs of the pathogen and symptoms of the disease (with pathogen signs only visible with the aid of a hand lens). Severity is a measure of fungal activity and is based on coverage of the foliage with visible signs of the fungus. The data were statistically analyzed using ANOVA and Waller-Duncan K-ratio t-test, (K = 100, P = 0.05).
Powdery mildew symptoms and signs were first observed in mid-July, and by mid-August disease pressure was heavy. By the date of the evaluation, untreated plants showed an incidence of 94 and severity of 72% powdery mildew, while standard fungicide treatments held the disease levels much lower (Table 1). As formulated, the MT 2000 1AS (1% aqueous suspension), when applied early and at the highest rate, showed some efficacy for powdery mildew management. Given the high disease pressure, Banner Maxx and Heritage were effective in suppressing powdery mildew.
With consumer concerns about the use of fungicides in the landscape, there is a need to evaluate biological control alternatives to standard fungicides. Landscape managers, arborists, and nursery operators will have an interest in knowing which fungicides will be capable of managing dogwood powdery mildew.
| Table 1. Efficacy of a biocontrol fungicide treatment and application timing compared to standard fungicides on powdery mildew of flowering dogwood. First applications were made 2 June (weekly applications began 30 June), and last applications were made 25 August. | ||||
| Treatment | rate/100 gal. | application frequency | Percent powdery mildew* | |
| Incidence | Severity | |||
| Banner Maxx 1.24MEC | 8.0 oz | triweekly | 4 a** | 7 a |
| Heritage 50WG | 8.0 oz | triweekly | 28 ab | 7 a |
| MT 2000 1AS | 1.5 gal | biweekly | 42 b | 19 ab |
| MT 2000 1AS | 1.0 gal | biweekly | 44 b | 25 abc |
| MT 2000 1AS | 1. 5 gal | triweekly | 49 b | 27 abc |
| MT 2000 1AS | 0.5 gal | biweekly | 76 c | 39 bcd |
| MT 2000 1AS | 1.0 gal | triweekly | 89 c | 28 abc |
| MT 2000 1AS | 1.0 gal | weekly | 83 c | 59 de |
| Check (water) | triweekly | 85 c | 52 cde | |
| MT 2000 1AS | 0.5 gal | triweekly | 80 c | 61 de |
| MT 2000 1AS | 0.5 gal | weekly | 92 c | 60 de |
| MT 2000 1AS | 1.5 gal | weekly | 94 c | 72 e |
| * Percent powdery mildew: Incidence = % foliage with symptoms and signs of disease; Severity = % foliage with visible signs of powdery mildew. ** In a column, means bearing the same letter are not significantly different (Waller-Duncan K-ratio test, P = 0.05). | ||||
Pest Management—Diseases
Landscape trees have long been afflicted with leaf scorch symptoms caused by environmental factors such as root damage, road salt, and drought and by wilt diseases caused by fungi (2). The association of xylem-limited bacteria with shade tree leaf scorch symptoms was first made in 1980 (7). In 1987, the bacterium associated with leaf scorch was described as a new species, Xylella fastidiosa (11). Bacterial leaf scorch has been reported in coastal U.S. states from New York to Texas and in Kentucky in bur, pin, red, and shingle oak; sycamore; sugar maple; and sweetgum (1,3,4,5,6,9,10). The disease is now being detected in southern Indiana and southern Ohio and has been diagnosed in Tennessee; thus, it is found throughout the eastern United States.
In oak, scorch symptoms first appear in late summer in individual branches where leaves show dead margins with green tissues near the main veins and leaf petiole. Often there is a fine yellow or reddish zone between brown and green tissues. Many affected leaves drop prematurely. In succeeding years, the late summer leaf scorch progresses to all parts of the tree. Gradually, infected trees suffer a chronic decline with branch dieback affecting more of the tree each year. Secondary factors can contribute to the tree demise, and eventually the tree needs to be removed. Tree decline, from first discovery of the disease to removal, may take place over a period of five to 10 or more years. It is not known how X. fastidiosa causes leaf scorch and defoliation of landscape trees, but water stress due to xylem occlusion seems to be the most likely cause (8).
In the Plant Pathology Department's Plant Disease Diagnostic Laboratory, we used an enzyme-linked immunosorbent assay (ELISA) developed for X. fastidiosa ("Pathoscreen-Xf," Agdia, Inc., Elkhart, IN) to detect the bacterium. When positive ELISA results are obtained from a new host or new geographic location, we confirm our findings by using electron microscopy to observe occluded xylem tissues and to observe the causal agent with its typical scalloped or undulating cell walls. The objective of this continuing research is to confirm the presence of Xylella in new locations on hosts showing symptoms of bacterial leaf scorch disease in Kentucky.
In 1987, we reported that bacterial leaf scorch was found in the following 17 Kentucky counties: Boyle, Caldwell, Campbell, Christian, Daviess, Fayette, Garrard, Hardin, Henderson, Hopkins, Jefferson, Jessamine, McCracken, Oldham, Pulaski, Union, and Warren. By 2000, an additional six counties are now on the list: Barren, Boone, Green, Marshall, Scott, and Taylor. The following landscape trees are now known to be hosts of bacterial leaf scorch in Kentucky:
a) oaks, including the following types: bur, pin, red, shingle, and white.
b) maples, including the following types: red, silver, Norway, and sugar
c) other deciduous trees, including sweetgum, sycamore, and London plane.
The disease is most serious and widespread on oaks, especially pin oaks. In some urban areas, mature pin oaks with bacterial leaf scorch have declined to such a great extent that they are now being removed. But the disease is by no means confined to older trees. We have diagnosed the disease on nursery trees and landscape "saplings" dying from bacterial leaf scorch. The disease is not widespread on maples and sweetgums in Kentucky, and bacterial leaf scorch-infected elms and mulberries, confirmed hosts in other states, have not been found in Kentucky.
Bacterial leaf scorch, exacerbated by last year's drought, is a major concern for arborists, nursery operators, and landscape managers because it is a very destructive disease. It is important for the industry to recognize the importance of bacterial leaf scorch and where it might be found in Kentucky.
Plant Evaluation
Annual and perennial garden flowers have been evaluated for many years at the University of Kentucky. Trials have occurred at the University of Kentucky Arboretum since 1993. These trials were expanded in 1999 and 2000 with grants from the Kentucky Department of Agriculture and the Kentuckiana Greenhouse Association. In 2000, 8000 square feet of trial gardens were initiated at the Horticulture Research Farm in Lexington, and 500-square-foot demonstration gardens were established at the Louisville Zoo, the Research and Education Center in Princeton, and the Purchase Area Master Gardeners Garden in Paducah. We plan to add demonstration gardens in other areas of the state in 2001.
We wish to thank the staff gardeners at all our garden locations for all their help with these trials. We are pleased to work with such knowledgeable and hard-working horticulturists across the state. Please take some time next year to visit these trial and demonstration gardens.
The following plants have been observed for at least three years. Those that are noted as not hardy were replanted each season just in case their performance over one season was not indicative of overall performance. The past several winters have been relatively mild, and the hardiness may be affected by a severe winter. Plants that did not survive the initial growing season are not listed. It is our feeling that perennial performance should be evaluated over a period of at least three years. When replacement plants were not available, any comment will be withheld until such time that these plants can be re-evaluated.
| Perennial Plants | ||||
| Name | Flower Color | Height | Season | Performance |
| Amsonia hubrichtii Narrow Leaf Amsonia | blue | 2-3 ft | early summer | Habit compact and more suitable for most border plantings. Not as invasive as Amsonia tabernaemontana |
| Crocosmia 'Jenny Bloom' | yellow | 28" | mid-summer | Period of bloom not extensive but still desirable for the garden. Plant not invasive. |
| Cuphea glutinosa Mexican Heather | light purple | 8-10" | mid-summer | Blooms are not that conspicuous. Good as a front-of-the-border plant or sunny ground cover. |
| Echinacea angustifolia Narrow-leafed Coneflower | lavender | 18-24" | summer | Lighter color than Echinacea purpurea with petals longer and more narrow. Not as vigorous. May be more difficult to establish. |
| Echinacea paradoxa Yellow Coneflower | yellow | 24-28" | summer | Not a common garden plant but has potential. Removal of spent blooms promotes rebloom. A change of pace from Rudbeckia. |
| Echinacea tennessensis Tennessee Coneflower | lavender | 18-24" | summer | Has great potential. Finer texture than Echinacea purpurea. Removal of spent blooms promotes rebloom. Considered an endangered species, but seed and plants are available from reputable sources. |
| Eupatorium rugosum 'Chocolate' Chocolate Leaf Snakeroot | white | 3-4 ft | late summer | Dark foliage is attractive even while the plants are not in bloom. Nice addition for the "native look." As blooms decline, plants become a little ragged looking. |
| Hibiscus coccineus Scarlet Mallow | red | 7-10 ft | summer | Dies back to the ground but very quick growing. Very exotic looking with 5" blooms. Great for a garden accent and tolerates wet locations. |
| Knautia 'Melon Pastels' | various | 18-24" | summer | Nice addition for the front of the border. Potential as a cut flower. |
| Lysimachia nummularia 'Aurea' Gold Moneywort | golden yellow foliage | 2-3" | summer | A low-growing ground cover. Good to brighten an area of the garden or front of the border. Not that invasive. |
| Monarda 'Petite Delight' PPAF Dwarf Bee Balm | pink | 12-14" | late summer | Not invasive, doesn't lodge, and appears resistant to powdery mildew. Nice plant. |
| Salvia madrensis 'Dunham' | yellow | 5-6 ft | late fall | Plants are not hardy. Blooms too late in the season to be useful. Often killed by frost before blooms completely show color. |
| Salvia 'Maraschino' Cherry Sage | red | 3-4 ft | summer | Small red blooms all summer. Not showy from a distance. Attracts hummingbirds. |
| Salvia gregii 'Sierra San Antonio' Yellow Texas Sage | yellow | 12-14" | summer | Not hardy. Bloomed most of the season but not as vigorous as other salvias. |
| Salvia microphylla 'Wild Watermelon' | red | 18-24" | summer | Not reliably hardy. Similar habit to S. 'Maraschino' |
| Salvia puberula 'Hidalgo' Hidalgo Mexican Sage | deep pink | 36-48" | late summer | Not hardy. Plants lodge and may require staking to maintain habit. Although not hardy, the striking distinct blooms are a welcome addition to the late summer garden. |
| Salvia 'Raspberry Royale' | deep pink | 3-4 ft | summer | Similar to 'Maraschino' but blooms a deep pink. |
| Salvia regla 'Jame' Orange Mountain Sage | orange | 18-24" | early fall | Not hardy. Blooms relatively large and attractive, but plants bloom too late in the season to be effective even as an annual. |
| Salvia uglinosa Bog Sage | blue | 5-6 ft | summer | Blooms all season. Habit rather rank. Can reseed and become invasive. Great for the "wild" look. Unpleasant foliage odor. |
| Tovara virginiana 'Painter's Palette' | 12-14" | all season | Grown for the effect of the variegated foliage. Prefers shade; slow growing; has potential as ground cover. | |
| Verbena 'Abbeyville' | light blue | 6-8" | summer | Begins bloom early but must be cut back to promote rebloom. |
| Verbena 'Appleblossom' | pink | 6-8" | summer | Blooms later in the spring than others. Must be cut back to promote rebloom. |
| Verbena 'Blue Prince' | blue | 6-8" | summer | Not hardy. Still has great potential as an annual. Great in containers. |
| Verbena canadensis 'Greystone Daphne' | lavender | 6-8" | summer | Not has hardy as some others. Probably not the best choice. |
| Verbena 'Fiesta' | pink/red | 6-8" | summer | Mottled blooms are very attractive. Like others, must be cut back after bloom to promote rebloom. |
| Verbena canadensis 'Lilac Time' | lilac | 6-8" | summer | Was in full bloom April 15, 2000. The earliest blooming of all the verbenas. Like others, must be cut back after bloom to promote rebloom. |
| Verbena peruviana | red | 2-3" | summer | Mat-like habit makes this one rather unusual. Consider for a very low ground cover. Must be cut back to promote rebloom. |
| Verbena 'Snowflurry' | white | 6-8" | summer | Not reliably hardy. Some plants did overwinter, but this is not a vigorous plant for us. There are better choices. |
| Veronica puduncularis 'Georgia Blue' Creeping Veronica | blue | 1-2" | early summer | Hardy and cute. Very bright and attractive when in bloom. Not invasive and could be a very attractive ground cover. Foliage persists through the winter. |
These perennials have been observed for only one summer:
Many annual flowers are grown each year in our trials and have a well-known performance record. The following plants were "new" this season in our trials or just deserved to be mentioned again. None had intensive maintenance requirements or exhibited any problems with diseases or pests. No information regarding this season's AAS trials is released until the judging process is complete and winners are designated.
| Annual Bedding Plants | ||||
| Name | Flower Color | Height | Season | Performance |
| Floss Flower Ageratum houstonianum 'Blue Horizon' | blue | 24-28" | summer | Although not new to the garden, this ageratum continues to be one of the best performers. Better than other ageratums with the added benefit of being a great cut flower. |
| Opal Cup Anoda | lavender | 24-28" | summer | Similar habit to a hollyhock. More of a novelty but useful for something different. No apparent pest or disease problems. Required no special maintenance. |
| Snapdragon Antirrhinum majus 'LaBella Mix', 'Light Pink Ribbon' | various | 18-24" | summer | Although they heat checked somewhat, these plants appeared fairly heat tolerant and produced blooms all summer. |
| Begonia 'Dragon Wing' | rose red | 18-24" | summer | Great performance from a large size begonia. Needs plenty of water and fertilizer for best performance. |
| Million Bells Calibrachoa 'Cherry Red', 'Terra Cotta' | rose red, salmon | 12-15" | summer | Commonly used for hanging baskets but excellent performance in ground beds. Flowered uniformly all summer. |
| Calibrachoa 'Liricashower Blue', 'Liricashower Rose', 'Trailing Pink', 'Trailing White' | blue, rose, pink, white | 4-6" | summer | Commonly used for hanging baskets but excellent performance in ground beds. Flowered uniformly all summer. |
| Vinca Catharanthus roseus'Stardust Orchid' | lilac with white center | 12-14" | summer | 2000 AAS Winner. Unique color. Performance similar to other vinca. |
| Angel Trumpet Datura meteloides | white | 3-4 ft | summer | Fast growing. Three plants covered a 6' x 8' portion of a flower bed. Large, showy white blooms. Good as a specimen plant. Plant parts poisonous. |
| Dianthus 'Melody Pink' | pink | 16-18" | summer | 2000 AAS Winner. Grass pink type of habit. Blooms were produced consistently all summer. Plan to observe for hardiness. |
| Gazania rigins Daybreak Series - 'Bright Orange', 'Bronze', ' Garden Sun', ' Pink Shades', ' Red Stripe', ' White', 'Yellow' | mixed | 12-14" | summer | Overall performance was mixed. The plants grew well and flowered well in early summer and fall, but they seemed to struggle more in the heat of summer. Self-sowed dramatically, probably not a good characteristic. |
| New Guinea Impatiens Impatiens hawkeri 'Java Mix' | mixed | 16-18" | summer | A New Guinea produced from seed that performed similarly to others. |
| Lantana camara 'Rainbow' | red and orange | 12" | summer | Common landscape plants in the South; heat and drought tolerant. This variety seems too small and too slow growing for garden use in Kentucky. |
| Lantana camara 'Cowboy', 'Tangerine', 'Weeping Lavender', 'White' | mixed | 12-18" | summer | Common landscape plants in the South; heat and drought tolerant. These varieties are easy to grow and perform well. |
| Lantana camara 'Confetti', 'Dallas Red', 'Irene', 'Patriot Hot Country', 'Patriot Sunburst' , 'Pink Caprice', 'Radiation', 'Rainbow', 'Samantha', | mixed | 18-24" | summer | Common landscape plants in the South; heat and drought tolerant. These varieties are easy to grow and perform well. 'Radiation' is our favorite because of bright red/orange flowers. |
| Lantana camara 'Dove Wing', 'Golden Plume', 'Lady Olivia', 'Miss Huff', 'New Red', 'Patriot Hallelujah' | mixed | 24-36" | summer | Common landscape plants in the South; heat and drought tolerant. These varieties are easy to grow and perform well but may be too large for many gardens. 'Miss Huff' may be hardy. |
| Blue Stars Laurentia axillaris | blue | 8-10" | summer | Small blue blooms were produced all summer. Has potential; will try again. No apparent pest or diseases, and no particular maintenance requirements. |
| Osteospermum 'Passion Mix' | various | 12-18" | early and late summer | Plants became leggy and floppy. Early bloom is very showy. Late bloom not as showy. Better in a mixed border because show is not consistent. AAS Winner. |
| California Bluebell Phacelia campanularia | blue | 3-5" | Plants burned out early. Bright blue blooms are very attractive, but the plants don't seem to tolerate our climate. | |
| Plumbago capensis 'Escapade Blue', 'Escapade White' | blue, white | 18-24" | summer | A common landscape flower in the South with good heat and drought tolerance. Seemed too slow growing and flowering for the Kentucky landscape. |
| Portulaca grandiflora 'Radiance Bicolor', 'Radiance Fuchsia' | fuchsia, fuchsia and white | 3-5" | summer | A large-flowered moss rose from cuttings. The fuchsia-colored flowers were spectacular in the landscape. |
| Castor Bean Ricinus communis 'Carmencita Pink', 'Carmencita Red' | seed heads pink or red | 8-10 ft | summer | Although seed set isn't apparent until later in the summer, these plants produce a quick annual hedge. Both could be very effective additions to the garden. |
| Fan Flower Scaevola aemula 'New Wonder' | blue | 8-12" | summer | Typically used in hanging baskets but an outstanding spreading plant with blue flowers in the landscape. |
| Bacopa Sutera cordata 'African Sunset', 'Lavender Storm', 'Snowstorm' | white, red, lavender | 2-4" | summer | Cool-season plants from cuttings generally used in containers. Did not tolerate our summer garden conditions well. |
| Mexican Sunflower Tithonia rotundifolia 'Fiesta Del Sol' | orange | 3-4 ft | summer | Past AAS Winner. Plants have a more compact habit and do not lodge late in the season but decline in late summer. Better choice than 'Torch' for this reason. |
| Verbena Verbena canadensis 'Abbyville', 'Batesville Rose', 'Blue Princess', 'Pink Sunrise', 'Temari Bright Red', Cherry Blossom Pink', 'Patio Blue', 'Violet', 'Tortuga Double Purple', 'Hot Pink', 'Peach', 'Red', 'White', 'Wildfire Dark Lavender' | various | 10-24" | summer | These verbenas have larger, less divided leaves. Temari and Tortuga verbenas flowered all summer and fall, while the others flowered sparsely in mid-summer. Tortugas seemed more susceptible to disease. Temari Patio Blue was the best of all verbenas in 2000. It flowered well all summer and produced a large mass of plants 24" tall. The other Temari verbenas performed well and remained a vigorous ground cover at 10 to 12". The Temari varieties remain our favorite after three years of trials. The unique or strong colors of Tortuga White, Red, and Hot Pink were attractive in the garden, but the plants did not perform as well as the others. |
| Verbena Verbena tenuisecta 'Aztec Lavender, 'Pink Magic', 'Babylon Lilac', 'Neon Rose', 'Silver', 'Tapien Blue Violet', 'Tapien Rose Pink' | various | 6-12" | summer | These verbenas have smaller leaves that are finely cut. In general, these plants do not flower well in mid-summer but flower profusely in spring, early summer, and fall. Plus, they are frost tolerant. Tapien verbenas were somewhat better in our trials. |
| Zinnia 'Profusion White, Cherry, Orange' | white, rose, orange | 14-24" | summer | AAS Winners. These disease-resistant zinnias should be in many commercial and residential gardens. Orange is somewhat better than White which is better than Cherry. No disease or maintenance problems. Great plants! |
| Swiss Chard 'Bright Lights' | yellow & red stems | 16-18" | summer | Great for the edible landscape. Foliage texture and stem color contrast well with many other plants. |
Plant Evaluation
A ground cover evaluation has begun at the University of Kentucky/Lexington Fayette Urban County Arboretum. Installation of plants occurred in May 2000.
A few tropical species were planted to see whether they would provide fast enough cover to be recommended as temporary or annual ground covers. Because of their lack of hardiness, these species would be treated as annuals in the landscape.
We believe these species may have potential as annual ground covers and will repeat this evaluation with increased fertilization and, in the case of Cissus and Setcreasea, with larger transplants.
Several perennials were added to the existing ground cover display at the Arboretum including several cultivars of Hedera helix and Sedum spp. These were evaluated for rate of establishment and initial spread. Hardiness will be evaluated in future years.
Several other perennials were planted for evaluation as ground covers. Among these were Albretia deltoidea `Whitewell Gem', Aurina sacatilis `Compacta', several cultivars of Phlox subulata, and several cultivars of hardy Geranium. These are slower to establish than those listed above, and their performance will be reported in future years.
Plant Evaluation
Evaluation of Hemerocallis daylily cultivars at the University of Kentucky Research and Education Center (UKREC) at Princeton is a result of the interest in daylilies that has created strong demand for plants and information on daylily cultivars. Daylily cultivars supplied by Kentucky hybridizers were evaluated for aesthetic appeal and favorable production characteristics.
Kentucky daylily cultivars for the 2000 trial were supplied by Thoroughbred Daylilies (T), Paris, KY; Schott Gardens (S) (for more on Schott Gardens cultivars see previous Research Reports), Bowling Green, KY; and Swanson Daylilies (Octavian = diploid and Milano = tetraploid), Lexington, KY.
Weekly observations were made on all cultivars in the evaluations to record time and color of bloom for the 2000 season. Daylilies were dug and divided on October 2, 2000 (Table 1). The divisions were replanted for further evaluation. Selected cultivars were distributed by the UKREC Nursery Crops Development Center (NCDC), Princeton, to the Floriculture Display Gardens at the UK Horticultural Research Farm in Lexington.
The bloom dates are reported as the first bud and the first bloom observed for any of the plants in the planting and the last bloom on any of the plants of a particular cultivar. The height of the scape is reported in inches. Irrigation was provided. The length of the bloom period can be influenced by the production system.
There continues to be an increase in the number of Kentucky nurseries producing daylilies and the number hybridizing daylilies. New cultivars with exciting characteristics such as John Rice's "white line" and "ruffled" edges in combination with watermarks, eye zones, and bands help maintain high levels of daylily sales to daylily collectors, gardeners, and landscapers. Evaluations of cultivars for time of flowering and number of divisions are important to a cultivar's economic survival. Three divisions per original plant is considered the absolute minimum in order for a cultivar to be considered commercially viable, and then only if the bloom characteristics are exceptional.
Knowledge of a cultivar's special bloom characteristics, i.e., early bloom, continuous bloom, or fall bloom, has been used to tailor marketing strategies. For example, a cultivar that bloomed during the fall festival season could expand the marketing diversity for roadside stands and entertainment farms as well as increase the length of the market window for daylily growers. Cultivars that bloom early and could be displayed in bloom during peak retail sales in the spring would also enhance sales.
Note: A single plant of each cultivar evaluated since the first daylily evaluation trial in 1992 has been planted in a display garden available for public viewing at the University of Kentucky Research and Education Center in Princeton. Some cultivars have been planted at the UK Arboretum in Lexington.
| Table 1. 2000 Kentucky daylily characteristic1 observations. | ||||||
| Cultivar | Date of First Bud | Date of First Bloom | Date of Last Bloom | Height (in.) | Color | Number of Divisions (proliferations) |
| Angel's Braid (T) | 15Jun | 30Jun | 5Oct | 15.0 | Yellow-lavender blush | NH |
| Baby Blanket (T) | 15Jun | 30Jun | 13Jul | 13.7 | Pink | 4 (1) |
| Candie Dwyer (T) | 07Jun | 26Jun | 02Aug | 17.5 | lavender | 4 |
| Chuck Wheeler (T) | 26Jun | 13Jul | 13Jul | 12.9 | Purple | 5 |
| Crown of Creation (T) | 02Jun | 05Jun | 24Jul | 17.8 | Gold-Orange | 3 |
| Dave Bowman (T) | 15Jun | 13Jul | 24Jul | 10.9 | Mauve w/ Burgundy eye | 4 |
| Magical Mystery(T) | 02Jun | 22Jul | 02Aug | 15.8 | Pale Burgundy | 3 |
| Mexican Siesta (T) | 02Jun | 05Jul | 13Jul | 12.0 | Dark Rose w/Yellow | 3 |
| Mystery Lover (T) | 02Jun | 26Jun | 05Jul | 21.2 | Purple Red | 6 (1) |
| Nancy Ligon (T) | 02Jun | 26Jun | 03Jul | 11.9 | Yellow Peach | 2 |
| Truly Angelic (T) | 16Jun | 05Jul | 07Jul | 18.4 | Pink-Lavender | 5 (1) |
| Wes Kirby (T) | 07Jun | 24Jul | 24Jul | 11.8 | Lavender | 4 |
| Upper Echelon (T) | 2Jun | 13Jul | 24Jul | 14.5 | Violet | 5 |
| Classic Rose | na | na | na | na | Pink | 9 |
| Neddie Downing(S) | na | na | na | na | Ivory | 4 |
| Ray Hammond (S) | na | na | na | na | Rust/Yellow | 4 |
| Mary Shadow (S) | na | na | na | na | Yellow/blush blush | 5 |
| Janice Wendell (S) | 02Jun | 26Jun | 02Aug | 25.7 | Yellow | 6 |
| Milano Maraschino | 02Jun | 15Jun | 05Jul | 26.8 | Wine/Yellow | NH |
| Milano Violet Mark | 02Jun | 20Jun | 05Jul | 23.9 | Violet | 6 |
| Milano Rocket | 02Jun | 15Jun | 13Jun | 23.8 | Burnt Orange | 2 |
| Octavian Marble Ring | 02Jun | 15Jun | 5Jul | 26.1 | Peach | 3 |
| Octavian Marble Model | 02Jun | 07Jun | 05Jul | 25.0 | Violet | 9 |
| Octavian Orchid | 02Jun | 07Jun | 05Oct | 25.1 | Purple Pink w/Yellow | 17 |
| Octavian Glow | 02Jun | 07Jun | 20Jun | 10.2 | Light Cream | 8 |
| Octavian Exotic Marble | 02Jun | 15Jun | 02Aug | 21.5 | Peach w/Violet Eye | 9 |
| Octavian Cherry Doll | na | 02Jun | 30Jun | 18.4 | Reddish Peach | 6 |
| 1 Color descriptions are limited and do not include throat colors, ruffling of edges, or edge color. See grower's catalog for more thorough descriptions. NB-no bloom observed NH-not harvested | ||||||
| Table 2. 1999 non-Kentucky daylily characteristic observations. | ||||||
| Cultivar | Date of First Bud | Date of First Bloom | Date of Last Bloom | Ht. (in.) | Color | Number of Divisions (proliferation) |
| Barbara Mitchell | 02Jun | 15Jun | 13Jul | 27.0 | Pink | NH |
| Siloam Virginia Henson | 07Jun | 26Jun | 05Oct | 21.2 | Pink w/Red Eye | 6 |
| Hyperion | na | na | na | na | Yellow | 6 |
| Happy Returns | na | na | na | na | Pale Yellow | 9 |
| Always Afternoon | 02Jun | 15Jun | 02Aug | 13.5 | Lavender/purple eye | 5 |
| Open Hearth | na | na | na | na | Yellow/red blush | 9 |
| Ruffled Apricot | na | na | 2Oct | na | Apricot | 4 |
| Buttercurls | 02Jun | 15Jun | 5Oct | 26.8 | Yellow | 12 |
| Chicago Sunrise1 | 02Jun | 20Jun | 02Aug | 28.0 | Orange | na |
| Eric Jr. | 02Jun | 26Jun | 28Jul | 29.4 | na | 39 |
| Lisa My Joy | 07Jun | 20Jun | 13Jul | 18.8 | off white/ purple eye | na |
| Anzac | 07Jun | 26Jun | 05Oct | 20.4 | orange | 10 |
| Pardon Me | 15Jun | 26Jun | 13Jul | 10.8 | red | 5 |
| Cantique | 07Jun | 20Jun | 30Jun | 9.3 | pink | 4 (1) |
| Juanita | 07Jun | 26Jun | 02Aug | 29.3 | Orange | 13 |
| Always Afternoon | 02Jun | 15Jun | 02Aug | 13.5 | mauve/purple eye | NH |
| Aten | 07Jun | 05Jul | 23Aug | 32.4 | Orange | 10 |
| 1 Chicago Sunrise had a fasciated scape. NH--Not harvested | ||||||
Plant Evaluation
This is the first year of a study at the UK Research and Education Center at Princeton evaluating Buddleia species and cultivars. Buddleia, or butterfly bush, is an attractive long-flowering shrub known for its long spiked flowers that attract butterflies. Plants grown from cuttings and averaging 6 to 8 inches tall were planted April 27, 2000.
Size of the plant at the end of the growing season is reported as spread, which is an in-the- row width measurement plus an across-the-row width measurement divided by two, and a height measurement (Table 1). Measurements were taken November 9, 2000, and are reported in inches.
The long season of flowering makes Buddleia an attractive landscape plant. It has been speculated that there is interest in new and underutilized Buddleia cultivars for use in landscapes and butterfly gardens. Buddleias may also be used for cut flowers. Following being cut to the ground, straight stems are produced with multiple flowers on each. It would appear that B. davidii `Flaming Violet' and B. yunnanensis offer potential as dried flowers. B. davidii `Flaming Violet' has dark stems and attractive seed heads. B. yunnanensis does not have colorful flowers but has silvery gray foliage and flower heads. Future evaluations will include cutting back the plants and evaluating their landscape characteristics and cut and dried flower potential.
Appreciation is expressed to Dwight Wolfe, June Johnston, and Hilda Rogers for assistance with this project.
| Table 1. Buddleia spread and height measurements.1 | ||||||
| Species/Cultivar | Spread | Height | Species/Cultivar | Spread | Height | |
| 'Pink Delight' | 44" | 25.5" | 'Flaming Violet' | 43" | 44"</ | |
