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April 20, 2005

This newsletter issue brings another phenology plant event: The redbuds are in bloom in central and southern Illinois and will soon be blooming in northern Illinois.

Zimmerman pine moth is susceptible to applications of permethrin in northern Illinois and may still be susceptible to treatment in central and southern Illinois. Zimmerman pine moth hatches in late summer into a small caterpillar that roams across and feeds a little on bark before finding a loose piece of bark to crawl under. There, the young caterpillar spins a thin silk case over itself, a hibernaculum, and stays there until spring. At this time of year, the larva leaves the hibernaculum and crawls across the bark of the tree for a few days until it locates a place to tunnel under the bark. During each of these wandering times by the small caterpillar, late summer and early spring, it is susceptible to insecticidal control.

Gypsy moth eggs will be hatching in northern Illinois in about 2 weeks and will be susceptible to Bacillus thuringiensis kurstaki and other insecticides. However, it is best to wait until the oak trees have leafed out enough to provide sufficient surface for the insecticide to land upon. This is normally about mid-May in northern Illinois.

Japanese beetle insecticide applications should be made by the end of April if you are using imidacloprid (Merit) as a soil application. It takes 2 months for imidacloprid to circulate up through the plant so that it is in the leaves when Japanese beetle adults start to feed in late June to early July. Realize that imidacloprid applied this way is effective on most trees and shrubs, but that there will be an occasional plant where the beetles will feed regardless of the treatment.

Author: Phil Nixon


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