Bagworms hatched a couple weeks ago and are still quite small. Therefore they can be difficult to find although they have constructed tiny bags that can be seen on leaves and needles of infested plants. It is easier to look for the large bags left from last year’s bagworm adults. These will be empty, but are a good indication that small bagworms are likely roaming a plant. This is because female bagworms are flightless and overwinter and lay eggs in their bags on trees and shrubs. Thus, baby bagworms hatch and grow up on the same plant as their mother was on the previous year.
Early in the year the best strategy is to hand pick the bags before eggs hatch to prevent infestations. Although it is too late for that now, at this point the small caterpillars have not eaten much or caused much damage. This increases dramatically as they will grow until they easily defoliate branches, causing unsightly ornamental plants. Small caterpillars are also much easier to kill than large ones. This is because they have less body mass to dilute toxins and their protective bags are not as thick. Therefore less toxic chemicals such as Bt formulations can be very effective when targeting small caterpillars. Other chemical options that are considered compatible with natural enemies are Acelepryn, TriStar, and spinosad. More information can be found in Ornamentals and Turf Insect Information Note No. 81.
Steve Bambara, NCSU Extension Entomologist