BeneficialBagworms

Bt for bagworms

Bacillus thuringiensis kurstaki · microbial insecticide
Against bagworms

Btk kills young bagworms feeding on arborvitae and juniper in early summer, while their bags are still only 1/8 to ¼ inch long. Maryland Extension says it must go on by mid-July, because it works well only on young bagworms. By August the caterpillars are too big for it. Pair it with hand-picking bags in winter, which removes the eggs before they ever hatch.

RateLabel rate — 4 tsp per gallon of water (Thuricide and Monterey B.t. shade-tree and ornamental directions)
TimingLate May to June, just after the eggs hatch and the young larvae stop ballooning; by mid-July at the latest. Repeat every 7–14 days while hatching continues

Before you order

A bacterium sprayed on leaves. Caterpillars that eat it stop feeding and die within a few days. It works only on the larvae of moths and butterflies, and has little or no effect on bees, lady beetles, lacewings or parasitic wasps. How it works, how to tell it has established and the supplier list are on the full Bacillus thuringiensis kurstaki profile.

Other controls for bagworms

No other reviewed control is listed for this pest yet.