by G.J. Mussey, D.A. Potter, and M.F. Potter, Entomologists
University of Kentucky College of Agriculture
Landscape managers in Kentucky contend with a wide vari- ety of plants and associated pest problems. In any given landscape, there may be hundreds of species and cultivars of native and exotic trees, shrubs, and garden plants. Throughout the growing season, these plants may be attacked by a similarly diverse assortment of insects, including wood borers, leafminers, scale insects, plant bugs, and leaf-feeding caterpillars.
Timing is everything when managing landscape pests. To be effective, insecticides or biological controls must be applied when pests are present and at their most vulnerable life stage. For example, scale insects are best controlled after the eggs have hatched but before the crawlers have formed a protective cover. Controlling wood borers requires treating host trees with insecticides to intercept the newly hatched larvae before they have penetrated the bark. Leaf-feeding caterpillars such as bagworms and tent caterpillars are easiest to control when the larvae are small. Timing is especially important when using short-lived materials such as summer oils, soaps, and Bacillus thuringiensis (BT).
Frequent in-field inspection is the most reliable means to detect insect problems and time control efforts. Unfortunately, regular monitoring is too time-consuming for many landscape managers. Field workers may not know when or where to look for vulnerable life stages or may not recognize them when encountered. Pests such as the holly leafminer, honeylocust plant bug, and potato leafhopper feed in advance of any recognizable damage. Pheromone traps are available for monitoring certain insects (e.g., clearwing borers) but require time and expertise to use effectively.
Forecasting Using Plant Phenology
Phenology is the science dealing with the effects of climate on seasonal biological events, including plant flowering and insect emergence. Insects are cold-blooded, and like plants, their development will be earlier or later depending on spring temperatures. Since both plant and insect development are temperature-dependent, seasonal appearance of particular insect pests should follow a predictable sequence correlated with the flowering of particular landscape plants. In a three-year research project, the seasonal development and emergence of 33 important insect pests were systematically monitored and tracked resulting in the creation of the timetable below. This information will help landscape managers and lay persons anticipate the appearance of important insect pests and effectively schedule control measures.
Using the Table
Beginning in early spring, the table predicts the sequence and date of emergence of particular insect pests of woody plants or turf (in bold type). Seasonal emergence of each pest is correlated with the flowering of 34 familiar landscape plants. First bloom (when a plant produces its first flower), 50 percent bloom, and 95 percent bloom (essentially full flower) are included to delineate distinct stages of flowering in the landscape. The table also lists average calendar dates of pest emergence during the three-year study, along with the range. Flowering tended to be a more reliable indicator of insect emergence than calendar date due to year-to-year temperature fluctuations.
Locate the pest you wish to monitor in the first column of the table. Flowering events that coincide with that pest's emergence appear in the same vicinity (above and below) of the table.
| Phenological sequence of woody plant flowering and insect events in Lexington, Kentucky. | |||||
| Insects | Phenological Indicator plants | Dates of pest emergence |
|||
Event |
3-year avg. |
Range |
|||
| Acer saccharinum (silver maple) | 1st bloom |
18 Feb |
12-23 Feb |
||
| Cornus mas (cornelian cherry dogwood) | 1st bloom |
21 Feb |
10 Feb-04 Mar |
||
| Acer saccharinum (silver maple) | 50% bloom |
24 Feb |
17 Feb-01 Mar |
||
| Cornus mas (cornelian cherry dogwood) | 50% bloom |
03 Mar |
26 Feb-13 Mar |
||
| Acer saccharinum (silver maple) | 95% bloom |
10 Mar |
03-22 Mar |
||
| Forsythia x intermedia (border forsythia) | 1st bloom |
12 Mar |
27 Feb-27 Mar |
||
| Cornus mas (cornelian cherry dogwood) | 95% bloom |
13 Mar |
29 Feb-23 Mar |
||
| Eastern tent caterpillar | Egg hatch |
16 Mar |
03-29 Mar |
||
| Forsythia x intermedia (border forsythia) | 50% bloom |
17 Mar |
05-29 Mar |
||
| Magnolia stellata (star magnolia) | 1st bloom |
19 Mar |
05-29 Mar |
||
| Rhododendron 'PJM' (P.J.M. rhododendron) | 1st bloom |
22 Mar |
07 Mar-02 Apr |
||
| Magnolia x soulangiana (saucer magnolia) | 1st bloom |
22 Mar |
04 Mar-04 Apr |
||
| Forsythia x intermedia (border forsythia) | 95% bloom |
23 Mar |
09 Mar-01 Apr |
||
| Pyrus calleryana 'Bradford' (Bradford pear) | 1st bloom |
23 Mar |
09 Mar-04 Apr |
||
| Magnolia stellata (star magnolia) | 50% bloom |
25 Mar |
09 Mar-07 Apr |
||
| Magnolia x soulangiana (saucer magnolia) | 50% bloom |
29 Mar |
09 Mar-11 Apr |
||
| Inkberry leafminer | Emergence |
01 Apr |
25 Mar-08 Apr |
||
| Pyrus calleryana 'Bradford' (Bradford pear) | 50% bloom |
01 Apr |
21 Mar-08 Apr |
||
| Pyrus calleryana 'Bradford' (Bradford pear) | 95% bloom |
03 Apr |
24 Mar-10 Apr |
||
| Rhododendron 'PJM' (P.J.M. rhododendron) | 50% bloom |
03 Apr |
31 Mar-07 Apr |
||
| Amelanchier arborea (serviceberry) | 1st bloom |
05 Apr |
30 Mar-11 Apr |
||
| Rhododendron 'PJM' (P.J.M. rhododendron) | 95% bloom |
06 Apr |
02-10 Apr |
||
| Berberis x mentorensis (mentor barberry) | 1st bloom |
06 Apr |
30 Mar-12 Apr |
||
| Acer platanoides (Norway maple) | 1st bloom |
06 Apr |
04-10 Apr |
||
| Magnolia stellata (star magnolia) | 95% bloom |
07 Apr |
04-11 Apr |
||
| Cornus florida (flowering dogwood) | 1st bloom |
08 Apr |
01-14 Apr |
||
| Boxwood psyllid | Emergence |
09 Apr |
04-16 Apr |
||
| Berberis x mentorensis (mentor barberry) | 50% bloom |
09 Apr |
30 Mar-18 Apr |
||
| Amelanchier arborea (serviceberry) | 50% bloom |
09 Apr |
08-12 Apr |
||
| Viburnum x juddii (Judd viburnum) | 1st bloom |
10 Apr |
08-13 Apr |
||
| Magnolia x soulangiana (saucer magnolia) | 95% bloom |
11 Apr |
08-14 Apr |
||
| Acer platanoides (Norway maple) | 50% bloom |
11 Apr |
08-14 Apr |
||
| Amelanchier arborea (serviceberry) | 95% bloom |
11 Apr |
08-14 Apr |
||
| Malus floribunda (flowering crabapple) | 1st bloom |
11 Apr |
08-15 Apr |
||
| Berberis x mentorensis (mentor barberry) | 95% bloom |
13 Apr |
02-22 Apr |
||
| Viburnum x juddii (Judd viburnum) | 50% bloom |
13 Apr |
11-17 Apr |
||
| Cercis canadensis (eastern redbud) | 1st bloom |
14 Apr |
11-17 Apr |
||
| Malus floribunda (flowering crabapple) | 50% bloom |
15 Apr |
13-20 Apr |
||
| Syringa vulgaris (common lilac) | 1st bloom |
15 Apr |
14-18 Apr |
||
| Acer platanoides (Norway maple) | 95% bloom |
15 Apr |
12-20 Apr |
||
| Aesculus x carnea (red horsechestnut) | 1st bloom |
16 Apr |
03-30 Apr |
||
| Malus sargentii (Sargent crabapple) | 1st bloom |
16 Apr |
13-22 Apr |
||
| Cornus florida (flowering dogwood) | 50% bloom |
17 Apr |
15-19 Apr |
||
| Cercis canadensis (eastern redbud) | 50% bloom |
17 Apr |
13-21 Apr |
||
| Viburnum x juddii (Judd viburnum) | 95% bloom |
17 Apr |
13-19 Apr |
||
| Prunus serrulata 'Kwansan' (Kwansan cherry) | 1st bloom |
19 Apr |
14-25 Apr |
||
| Prunus serrulata 'Kwansan' (Kwansan cherry) | 50% bloom |
19 Apr |
17-21 Apr |
||
| San Jose scale | Egg hatch |
20 Apr |
20 Apr |
||
| Honeylocust plant bug | Emergence |
20 Apr |
13-29 Apr |
||
| Syringa vulgaris (common lilac) | 50% bloom |
20 Apr |
18-24 Apr |
||
| Malus sargentii (Sargent crabapple) | 50% bloom |
20 Apr |
16-26 Apr |
||
| Prunus serrulata 'Kwansan' (Kwansan cherry) | 95% bloom |
20 Apr |
18-23 Apr |
||
| Birch leafminer | Emergence |
21 Apr |
20-23 Apr |
||
| Malus floribunda (flowering crabapple) | 95% bloom |
21 Apr |
18-25 Apr |
||
| Cercis canadensis (eastern redbud) | 95% bloom |
21 Apr |
18-24 Apr |
||
| Cornus florida (flowering dogwood) | 95% bloom |
22 Apr |
20-24 Apr |
||
| Hawthorn lace bug | Emergence |
22 Apr |
19-27 Apr |
||
| Malus sargentii (Sargent crabapple) | 95% bloom |
23 Apr |
20-28 Apr |
||
| Oystershell scale | Egg hatch |
23 Apr |
20-30 Apr |
||
| Magnolia weevil | Emergence |
23 Apr |
18 Apr-01 May |
||
| Viburnum plicatum var. tomentosum
(doublefile viburum) |
1st bloom |
23 Apr |
22-27 Apr |
||
| Black cutworm | 1st flight |
24 Apr |
22-26 Apr |
||
| Syringa vulgaris (common lilac) | 95% bloom |
24 Apr |
20-29 Apr |
||
| Lilac borer | 1st flight |
24 Apr |
18-30 Apr |
||
| Lonicera tatarica (tatarian honeysuckle) | 1st bloom |
25 Apr |
20 Apr-03 May |
||
| Viburnum plicatum var. tomentosum
(doublefile viburnum) |
50% bloom |
26 Apr |
23-30 Apr |
||
| American plum borer | 1st flight |
26 Apr |
20 Apr-03 May |
||
| Holly leafminer | Emergence |
27 Apr |
24 Apr-01 May |
||
| Crataegus viridis 'Winter King'
(Winter King hawthorn) |
1st bloom |
27 Apr |
23 Apr-04 May |
||
| Cornus kousa (flowering dogwood) | 1st bloom |
28 Apr |
18 Apr-10 May |
||
| Chionanthus virginicus (white fringe tree) | 1st bloom |
28 Apr |
22 Apr-06 May |
||
| Aesculus carnea (red horsechesnut) | 50% bloom |
29 Apr |
26 Apr-03 May |
||
| Lesser peachtree borer | 1st flight |
29 Apr |
24 Apr-07 May |
||
| Pine needle scale | Egg hatch |
30 Apr |
25 Apr-07 May |
||
| Viburnum plicatum var. tomentosum | |||||
| (doublefile viburnum) | 95% bloom |
01 May |
29 Apr-03 May |
||
| Chionanthus virginicus (white fringe tree) | 50% bloom |
01 May |
27 Apr-09 May |
||
| Crataegus viridis 'Winter King'
(Winter King hawthorn) |
50% bloom |
02 May |
27 Apr-08 May |
||
| Redbud leafhopper (E. aclys) | Emergence |
02 May |
28 Apr-04 May |
||
| Redbud leafhopper (E. bistrata) | Emergence |
02 May |
28 Apr-04 May |
||
| Pyracantha coccinea (scarlet firethorn) | 1st bloom |
02 May |
01-07 May |
||
| Lonicera tatarica (tatarian honeysuckle) | 50% bloom |
02 May |
27 Apr-07 May |
||
| Boxwood leafminer | Emergence |
03 May |
02-04 May |
||
| Euonymus scale | Egg hatch |
04 May |
01-07 May |
||
| Aesculus carnea (red horsechestnut) | 95% bloom |
04 May |
02-06 May |
||
| Cornus kousa (kousa dogwood) | 50% bloom |
04 May |
26 Apr-15 May |
||
| Chionanthus virginicus (white fringe tree) | 95% bloom |
05 May |
30 Apr-11 May |
||
| Crataegus viridus 'Winter King'
(Winter King hawthorn) |
95% bloom |
06 May |
04-12 May |
||
| Potato leafhopper | 1st activity |
07 May |
03-14 May |
||
| Pyracantha coccinea (scarlet firethorn) | 50% bloom |
08 May |
06-10 May |
||
| Cladrastris kentukea (yellowwood) | 1st bloom |
08 May |
05-11 May |
||
| Ilex opaca (American holly) | 1st bloom |
08 May |
05-11 May |
||
| Lonicera tatarica (tatarian honeysuckle) | 95% bloom |
11 May |
02-21 May |
||
| Ilex opaca (American holly) | 50% bloom |
11 May |
08-14 May |
||
| Cladrastris kentukea (yellowwood) | 50% bloom |
12 May |
10-15 May |
||
| Cornus kousa (kousa dogwood) | 95% bloom |
13 May |
05-24 May |
||
| Pyracantha coccinea (scarlet firethorn) | 95% bloom |
14 May |
13-16 May |
||
| Juniper scale | Egg hatch |
15 May |
13-18 May |
||
| Ilex opaca (American holly) | 95% bloom |
17 May |
17-18 May |
||
| Cladrastris kentukea (yellowwood) | 95% bloom |
17 May |
17-18 May |
||
| Bagworm | Egg hatch |
18 May |
18-20 May |
||
| Dogwood borer | 1st flight |
20 May |
19-23 May |
||
| Crataegus phaenopyrum
(Washington hawthorn) |
1st bloom |
21 May |
18-26 May |
||
| Bronze birch borer | Emergence |
22 May |
18-25 May |
||
| Tilia cordata (littleleaf linden) | 1st bloom |
23 May |
02 May-07 Jun |
||
| Syringa reticulata (tree lilac) | 1st bloom |
23 May |
19-30 May |
||
| Catalpa speciosa (northern catalpa) | 1st bloom |
24 May |
21-26 May |
||
| Calico scale | Egg hatch |
24 May |
24-26 May |
||
| Crataegus phaenopyrum | |||||
| (Washington hawthorn) | 50% bloom |
24 May |
21-28 May |
||
| Hydrangea quercifolia (oakleaf hydrangea) | 1st bloom |
27 May |
23 May-02 Jun |
||
| Catalpa speciosa (northern catalpa) | 50% bloom |
27 May |
26-29 May |
||
| Flatheaded appletree borer | Emergence |
28 May |
20 May-06 Jun |
||
| Crataegus phaenopyrum | |||||
| (Washington hawthorn) | 95% bloom |
28 May |
26 May-01 Jun |
||
| Syringa reticulata (tree lilac) | 50% bloom |
29 May |
24 May-05 Jun |
||
| Peachtree borer | 1st flight |
29 May |
26 May-05 Jun |
||
| Twolined chestnut borer | Emergence |
29 May |
26 May-01 Jun |
||
| Magnolia grandiflora (southern magnolia) | 1st bloom |
30 May |
23 May-12 Jun |
||
| Catalpa speciosa (northern catalpa) | 95% bloom |
31 May |
30-31 May |
||
| Syringa reticulata (tree lilac) | 95% bloom |
02 Jun |
28 May-07 Jun |
||
| Hydrangea quercifolia (oakleaf hydrangea) | 50% bloom |
02 Jun |
31 May-06 Jun |
||
| Japanese beetle | 1st flight |
04 Jun |
03-08 Jun |
||
| Tilia cordata (littleleaf linden) | 50% bloom |
07 Jun |
04-09 Jun |
||
| Honeylocust borer | Emergence |
07 Jun |
26 May-15 Jun |
||
| Hydrangea quercifolia (oakleaf hydrangea) | 95% bloom |
07 Jun |
05-11 Jun |
||
| Magnolia grandiflora (southern magnolia) | 50% bloom |
08 Jun |
26 May-20 Jun |
||
| Walnut scale | Egg hatch |
09 Jun |
08-11 Jun |
||
| Tilia cordata (littleleaf linden) | 95% bloom |
09 Jun |
06-13 Jun |
||
| Cottony maple leaf scale | Egg hatch |
11 Jun |
08-14 Jun |
||
| Koelreuteria paniculata (golden-rain tree) | 1st bloom |
16 Jun |
13-18 Jun |
||
| Abelia x grandiflora (glossy abelia) | 1st bloom |
23 Jun |
14 Jun-09 Jul |
||
| Koelreuteria paniculata (golden-rain tree) | 50% bloom |
24 Jun |
21 Jun-01 Jul |
||
| Koelreuteria paniculata (golden-rain tree) | 95% bloom |
26 Jun |
23 Jun-01 Jul |
||
| Obscure scale | Egg hatch |
06 Jul |
05-08 Jul |
||
Determining Treatment Date
For most insects listed in the table, the ideal time to begin insecticide treatment is at or shortly after pest emergence. For bagworms, delay treatment one to two weeks after eggs hatch to ensure all young larvae have emerged from the old bags. For clearwing borers (dogwood, lilac, peachtree, lesser peachtree) and American plum borer, apply a bark spray 10 to 14 days after first flight. Apply a second bark spray one month later for better control of dogwood, peachtree, and lesser peachtree borers. For flatheaded borers (bronze birch borer, flatheaded appletree, honeylocust, twolined chestnut borer), apply a bark spray at or shortly after emergence and repeat after three weeks.
Revised: 4/07
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!
