ORNAMENTALS AND TURF
From: Steve Frank, Extension Entomologist
Azalea Caterpillars
Azalea caterpillars, Datana major, are among our most attractive caterpillar species. They feed primarily on Rhododendron spp., but this week we also found them on blueberries. They are most evident late in the summer. There is one generation of this pest each year. Adults lay eggs on the underside of azalea leaves where the small caterpillars feed gregariously. As they grow the caterpillars take on the coloration seen in the picture below. Unfortunately, by the time they are noticed azalea caterpillars can consume a lot of foliage and defoliate a shrub. Scout for these caterpillars by scanning shrubs for bare twigs then look closer to investigate. If you find a group of them, prune the branch out. In larger infestations or nurseries there are several insecticides active on caterpillars, but any product works best on small stages.
Azalea caterpillars. Photo: Adam Dale, North Carolina State University.
Redheaded Pine Sawfly
This week we had a clinic report of pine defoliation on campus. The culprit is probably the redheaded pine sawfly, Neodiprion lecontei. It is a pest of pines in ornamental landscapes, nurseries, and plantations. Adults emerge in spring and a second generation occurs in mid-summer. Eggs are laid on many two and three needled pine species such as Jack pine, loblolly pine, and red pine. Sawflies are not flies and the larvae do not turn into butterflies. They are non-stinging herbivorous wasps. They can defoliate trees and bushes in the landscape. Since they are gregarious it is sometimes possible to prune an infested branch and remove all the larvae. Management for sawflies is similar to caterpillar management though not all the insecticides will work so check the label. Horticultural oil is a good bet especially for small larvae. Formulations that contain azadirachtin or spinosad are also effective. For sawflies and caterpillars, management of full grown caterpillars is generally not warranted. The damage is already done and they are hard to kill.
Redheaded pine sawflies on Pinus uncinata. Photo: S. D. Frank.
From: Mike Munster, Ornamental Pathologist, Plant Disease and Insect Clinic
Box Blight Confirmed in Wake County
Box blight has been confirmed in boxwood plants originating in a nursery in the North Carolina mountains and offered for sale at the North Carolina State Farmers Market in Raleigh. The disease also has been confirmed at the Raleigh home of the vendor. A small number of customers may have purchased infected plants between the beginning of July and mid-August 2014.
Box blight is a destructive fungal disease of boxwood leaves and twigs. Symptoms include brown leaf spots, dark streaks on twigs, and extensive leaf drop. Sarcococca (sweetbox) and Pachysandra can also become infected. A fact sheet (http://www.ces.ncsu.edu/wp-content/uploads/2013/05/Box-blight-Guide-07.22.13.pdf) is available with additional information about identification and management of this disease. Note that sanitizer information is currently being updated. For most bleach formulations the correct ratio of bleach to water is now1:14.
Personnel from the North Carolina Department of Agriculture and Consumer Services are attempting to trace the sales of these plants from the Farmers Market. Careful removal and destruction of all infected shrubs may help keep losses to a minimum and prevent further local spread. If you believe you may have purchased one of the plants in question, please contact the office of Phil Wilson, Plant Pest Administrator for the North Carolina Department of Agriculture & Consumer Services at 919-707-3753. Other parties with questions about box blight should direct them to their local County Cooperative Extension Service office.
For more information contact your local Cooperative Extension Center and ask for the Commercial Horticulture Agent.
