No. 4/May 14, 2010
Roundheaded Appletree Borer
Most roundheaded borers attack dying or dead trees, but there are a few exceptions, Asian longhorned beetle, linden borer, and roundheaded appletree borer being among them. Roundheaded appletree borer attacks rose family plants including hawthorn, mountain ash, quince, serviceberry (shadbush), cotoneaster, and crabapple.
Flatheaded Appletree Borer
Flatheaded appletree borer attacks trees in the rose family, being common in older hawthorn, serviceberry, cotoneaster, rose, and crabapple branches and trunks where it primarily attacks declining trees and shrubs near the end of their lifespan.
Mimosa webworm is susceptible to control at this time in southern Illinois. Spraying the foliage of attacked trees with Bacillus thuringiensis kurstaki (Dipel, Thuricide), spinosad (Conserve), or labeled pyrethroid insecticide at this time should provide control.
Daylily Leaf Streak
Daylily foliage is looking lush in most parts of the state. In some of the wetter areas we have seen daylily leaf streak.
Crabapple Scab Note
Although we have not seen much in the way of apple scab in Champaign/Urbana as yet, it is beginning. Temperatures have been above average and moisture below average, until this past week.
Birch Anthracnose, Chlorosis, and More
Anthracnose is a common spring disease, especially in cool, wet conditions. Since those conditions occur in Illinois every year, we see anthracnose every year. There are many fungi that cause anthracnose diseases on many hosts. It is not just one big, powerful pathogen.
Japanese Tree Lilac Diseases
Japanese tree lilac (Syringa reticulata) has become a very popular plant in Illinois. The good news is that so far the disease problems seem few and sparse.