May 9, 2021

Be On the Lookout for Bagworms!

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There’s a fairly new villain in our area, and it’s coming after your trees and bushes. Bagworms’ favorite victims are junipers, arborvitaes, cedars and spruces, but they will happily destroy maples and just about anything else.

The cocoons or “bags” in the photo were created by female bagworm moths last Fall. Into each bag a female laid up to 1,000 eggs. Then they cleverly camouflaged the bags with bits of the host plant. At only 1-2 inches long, and half as wide, they are easy to miss. In mid to late Spring the eggs will hatch into pin head sized black larvae that are very hungry. After they have defoliated their host tree, they spin silk threads to use as parachutes to reach nearby trees, where they will spin a new bag for themselves. By late Summer, they have metamorphosized into adult moths. The males mate with the wingless females, eggs are laid, and the cycle continues.

Now is the time to destroy the bags before the eggs hatch. The most effective method is to hand cut them from the host plant, and submerge them in a bucket of hot, soapy water. If the eggs have already hatched, you can apply the bacteria Bacillus thuringiensis with a garden sprayer every 7-10 days until they are eliminated. As a last resort, Ortho Tree & Shrub insect killer is effective while they are still young.

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