Monday, September 10, 2012

Pest News for September 10

From: Steve Frank, Extension Entomologist

Yellownecked Caterpillars

Adult yellownecked caterpillars, Datana minstra, occur in June or July and lay eggs on deciduous shrubs and trees. They will feed on many fruit and ornamental trees including birch, elm, oak, maple, Prunus spp. and others. They feed gregariously in late summer. They consume entire leaves except large mid-veins and can rapidly defoliate trees or cause significant damage. I found the caterpillars pictured below in the forest on a bush I couldn't identify because every leaf was gone. Scouting for small caterpillars can help reduce damage and improve control if it is needed. Caterpillar management information is available: See more caterpillars on my blog:

Redheaded Pine Sawfly

The redheaded pine sawfly, Neodiprion lecontei, 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 2 and 3 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 off an infested branch and remove all the larvae. Management for sawflies is similar as for caterpillars 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.

From: Mike Munster, Ornamental Pathologist, Plant Disease and Insect Clinic, and Kelly Ivors, Extension Plant Pathologist

Poinsettia Scab

Poinsettia scab, caused by the fungus Sphaceloma poinsettiae, was found on a sample from a commercial greenhouse this week. It has been six years since the PDIC last diagnosed this disease in a North Carolina poinsettia crop. As the name implies, this fungus causes leaf spots and stem lesions, but the most noticeable effect is an abnormal elongation of the poinsettia stem. The purple leaf spots may develop a light tan center, and they sometimes have a yellow halo. The surface of the spot is characteristically puckered, which is best seen under magnification. An olive-colored, velvety layer of spores may be present on the spots and stem lesions. These spores are spread to other plants via water splash. Long-distance transport occurs on infected planting material. This disease cannot survive between seasons in North Carolina in the absence of a poinsettia crop. For a good summary of the disease, see the 2001 APSnet publication by Mike Benson et al. ( Growers should be sure they get clean stock and should scout points for leaf and stem symptoms. Keeping leaf wetness to a minimum will help reduce the advance of the disease. Apply azoxystrobin (Heritage), trifloxistrobin (Compass O), triflumizole (Terraguard) or triadimefon (Strike) to protect plants.

For more information contact your local Cooperative Extension Center and ask for the Commercial Horticulture Agent.