Issue 11, July 12, 2013


Bagworms continue to be numerous in some areas of the state. Although they continue to grow and get bigger, a high level of control can still be achieved. Pupation will occur in the second half of August in southern Illinois to early September in northern Illinois. The insects are large enough to make hand removal very effective with small populations on shorter trees and shrubs. Do not just drop them on the ground; they will climb back up the tree. Squash them or collect them and dispose of them in the trash.

Bagworms Feeding on Arborvitae

Insects in general tend to get harder to control with insecticides as they get older and larger, but it happens in bagworms more than many other insects. Bacillus thuringiensis kurstaki, sold as Dipel, Thuricide, and many other brands, will still be effective, but its efficacy starts to fall off with these larger caterpillars. Expect control around 80-90% with good coverage instead of the 97-100% achieved with younger, smaller caterpillars. Pyrethroids, such as cyfluthrin (Tempo), lambda-cyhalothrin (Scimitar), and permethrin (Astro), should still provide 99-100% control. Spinosad (Conserve) should also provide a very high level of control.

Phil Nixon

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