Bagworms Have Hatched
The bagworm, Thyridopteryx ephemeraeformis, is a very common pest of Leyland cypress, juniper, arborvitae and cedar throughout the eastern United States. These pests have been hatching for the last few weeks in our area but are difficult to detect. Look for browning in evergreen plants and the tiny caterpillars with tiny upright green bags. You might also find larger brown bags remaining from last year.
Bagworms overwinter as eggs within the mother’s bag. Larvae emerge from the bag during May and June depending on location and temperature. The larvae crawl or drift via silk strands to nearby foliage where they begin to feed. Bagworms are relatively sedentary during their lifetime, usually remaining in the same area until they pupate. The larvae feed on foliage during the summer as they grow and mature. When fully grown the larvae permanently suspend their bags from twigs and change into pupa. Adult females are wingless and of course do not fly nor leave the tree. Male bagworms develop into a small brown moth.
Bagworms feed on plant foliage and heavy infestations can defoliate trees and shrubs. Young caterpillars produce a silk bag on their posterior end that gradually collects plant material. This creates a bag covered in leaves or plant debris that camouflage them from predators. Since they do not move much as larvae they can build up dense populations.
Management of these insects can be difficult and time consuming since they are protected inside the bag. One of the most effective, yet time consuming methods of treatment are hand-picking or cutting the female pupae bags off of the branches. This treatment is best timed in fall, winter or early spring before the eggs hatch. When this is impractical or impossible, there are chemical control options available that should be applied when caterpillars are young. They are in this stage right now. Several products are available for homeowner use such as azadirachtin, spinosad, permethrin, cyfluthrin, Bacillus thuringiensis (BT) and bifenthrin provide satisfactory results. The BT products have very low toxicities, but are only effective against younger larvae. Foliage should be thoroughly wetted with the insecticide spray in order to achieve thorough coverage. Bagworms are susceptible to predation from parasitoids and birds that assist in their control.
These evergreens are beautiful especially during winter. Efforts now to keep bagworms under control will pay off in years to come