Bagworm egg hatch usually occurs in late May in central Kentucky but, as with most things, is well ahead of schedule this year. Eggs survive the winter in the bags that contained last year’s females. Hatch occurs following the accumulation of 65 to 75 degree days. That target was reached in central Kentucky between May 1 and May 5 this year, about three weeks ahead of schedule. Eggs hatch over a four to five week period, which means the insect will be active for some time and one control measure may not be enough. Bagworms commonly catch people off guard; the infestation is not recognized until significant damage is done. It is even more likely with the early onset of feeding this year.
Bagworms are a nemesis because damage can be significant unless a good control strategy is followed. Four important elements are:
1) Effective spray timing — which is now, egg hatch is underway statewide.
2) Thorough coverage means being sure that an insecticide application reaches deep into the canopy or shrub. Treatment of just the outer foliage will not reach bagworm feeding deeper in the plant structure.
3) Treat all infested trees and shrubs, not just ones that are heavily infested.
4) Finally, apply a follow-up or clean-up treatment about three weeks later to control bagworms from late-hatching eggs.
A number of effective products are available for bagworm control. Using them effectively provides the best results. Liquid Sevin, Talstar, Ortho Max Lawn and Garden insect killer, and Bonide Eight insect control are just some of the insecticides that are available. Always read and follow directions on the label.
Jerry Little is Boyle County extension agent for agriculture/natural resources.