Lexington, Kentucky 40546
      
Nursery Update - A Kentucky Cooperative Extension Service Update for the Kentucky Nursery Industry
    
By Amy Fulcher, Extension Associate - Nursery Crops
University of Kentucky Department of Horticulture
Update #33
July 18, 2005

Insects
Got Mites?

Many growers are experiencing rapidly increasing mite populations. So far honeylocusts are looking very healthy even with mite numbers of 25-50 (per leaf) from one bang with a bang board test. Maples are beginning to bronze with populations well over 100 mites per leaf, with Autumn Blaze maple being one of the hardest hit. We don't know if this impacts growth but container growers want to be aware of the consequences of high mite populations on plant appearance. Hydrangeas, magnolias, and burning bush are also being attacked by spider mites. While we commonly see two spotted spider mites on many plants in greenhouses, and on roses and burning bush in the landscape, we seldom see them on other landscape plants that haven't been in a greenhouse environment. Often another mite species is involved that may or may not behave like two spotted spider mite. Knowing which spider mite species you have can go a long way in determining how to manage that pest.

Be careful of assuming that a dead area on dwarf Alberta spruce is from a current mite population. During the hot summer months those cool season mites general die off with only eggs remaining. A close inspection will show that no mites are present. Damage just became visible because the hot, dry summer weather dried out the damaged tissue.

Many miticides and predatory mites are available. There are several factors to consider when selecting a control: whether or not you have other foliar insect pests, when the area needs to be entered by workers without personal protective equipment, whether the mite is a warm or cool season mite, portion of the mite population that is adult, interest in preserving beneficials, impending weather, cost, frequency of children in the production area, availability, etc.

A Success Story:
A central Kentucky container grower recently had tremendous control with 2 species of predatory mites at a cost of $100 plus $25 for shipping. This treated approximately a 3000 sq. ft. area. Two days after application there was no sign of mites. The application allowed continuous work in the treated area by nursery employees.

Brief notes on a few miticides:
Floramite®:
Label allows only 2 applications per crop per year.
Growers have been very pleased with success but caution against making the two applications consecutively (the label suggests making at least two alternative applications before returning to Floramite® in the Strategies for Resistance Management section).
Compatible with predatory mites and beneficial insects.

Hexagon®:
Label allows one application per crop cycle or once per year.
Controls only larvae and eggs.
Compatible with predatory mites and beneficial insects.

Avid®:
Can be mixed with oil - use caution and test on a small number of plants only after reading the Avid and oil label carefully.
May control other foliar pests.

All three have a reentry interval of 12 hours.

Use of trade or brand names in this publication is for clarity; it does not imply approval of the product to the exclusion of others which may be of similar, suitable composition, nor does it guarantee or warrant the standard of the product.

Source: Scouting numbers supplied by Derrick Hammons, courtesy of KY IPM.

 
Cultural
While the hurricane has meant rain and relief for Kentucky, the typical hot, dry summer days are likely to resume. Drying for just a day can spell disaster for container plants. The Celestial™ dogwoods below went without water for 2 days the last week of May, back when weather conditions were more mild. The plant on the left had a high rate of controlled release fertilizer applied in the spring. The plant on the right had the medium rate. Notice the marginal scorch on those plants fertilized at the higher rate.

Be sure to check the pH as water quality changes during the course of the summer. Be sure that you haven't overwatered trying to compensate for dry weather. Pull plants out of containers and look for healthy white roots. Conduct a pour through test to determine if you have leached fertilizer. Be very careful in applying a controlled release fertilizer mid summer and later. One tremendous advantage of water soluble fertilizer is that it can be turned on to carry a crop through the late season and then turned off to allow plants to harden for winter. It allows complete control by the grower.
 
Above: Medium fertilizer rate (spots are fungicide residue)

Above: High fertilizer rate

 
 

Nursery Management Workshop

"Plan for Success"

Owners and Managers of the Garden Center, Lawn & Landscape and Nursery Industry

Tuesday, August 2, 2005
University of Kentucky Research and Education Center
1205 Hopkinsville Street
Princeton, KY

$35 per person
(or $30 for 2 or more from the same company)

Topics include: Setting and Meeting Goals, Employee Management, Market Plan & Setting Goals, Avenues of Marketing, Industry Trends, Round Table Discussions

 Contact: Dava Hayden at 270/365-7541 ext. 279, Dava.Hayden@uky.edu

Sponsored by: The Kentucky Horticulture Council and WKNLA

Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability, or national origin.

Scouting Report
It is time for the second insecticide application for peachtree borer. Maple mites and honeylocust mites are developing very high populations in some areas. Powdery mildew is visible as is heat scorch on Cornus florida, flowering dogwood. Inspect rapidly wilting and dying crabapples for southern blight and maples, smokebush, magnolias and others for verticillium wilt. Check oaks for bacterial leaf scorch. Set out traps for banded ash borer. Plan for your fall preemergence herbicide. Plan seeding and reseeding row middles and/or driveways in August and September. Please consult the IPM Calendar for Deciduous Tree Production for specific spray recommendations and a more complete listing of species to scout.

Source: Scouting report provided in part by Derrick Hammons, courtesy of KY IPM.

Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability, or national origin.
Note: Trade names are used to simplify the information presented. No endorsement by the Kentucky Cooperative Extension Service is intended, nor is criticism implied of similar products that are not named. Always read product label before use.