Euonymus webworm (also known as Euonymus caterpillar) has been found as young larvae in northeastern Illinois. This insect was present in large num bers last year in this part of the state, particularly on European euonymous.
Look for larvae in small webs. The webs increase in size as the larvae feed on the leaves and can become large. The slender caterpillars are a very pale yellow with black spots and can grow up to almost 1 inch long. Bacillus thuringiensis var. kurstaki (Bt) will control young larvae but is less effective on mature larvae. Penetrate the web thoroughly with Bt, as the insect must eat the Bt for it to work. Other insecticides are also effective.