So, I’m outside taking in the breeze of the morning. The birds are busy with tending bird business. Our bees are busy being bees and Betty has made a cool bed under the Mock Orange bush supporting my effort to share interesting points of interest about the notorious Bagworm.
Bagworms have a busy one generation life cycle with activity in all four seasons. The female has the ability to produce over 1,000 eggs. She will lay them inside an old bag attached to a tree and they will winter over inside the bag.
We are in the the month of June and this is when the insects will hatch in to caterpillars. The newly hatched worms will begin to spin a new bag, grow and become large enough to crawl out of the old bag to feed. Evergreens are the host plant source; arborvitae, junipers and others. The bags are camouflaged on the limbs within the tree and are often not noticed until the damage they cause appears. The caterpillar will crawl out to feed, but if something disturbs it, it will retreat back inside making it nearly impossible to pull them out. How small you ask? Look at one of those bags left from last year and then shrink it down to under one-half an inch in length. Yep, they’re that small.
The damage from feeding becomes noticeable in July and August. The leaves are stripped from the branches and if untreated, the tree will die. Oftentimes, feeding begins at the top of the evergreen, travels downward until the tree is destroyed. The natural behavior is to consume the host plant before moving to the next plant.
Bagworms reach maturity and begin mating in early fall. A male bagworm will be a blackish moth with transparent wings, whereas a female does not have wings and does not leave the bag. The bag size will be about 2 inches in length. Pesticides will be ineffective to destroy the bagworms once maturity is reached. Actually, by the time most people notice bagworm (mid to end of July), pesticides are much less effective due to the size of the worm versus the amount of food they are ingested. So, like our Ag Educator told me, if you have a problem, mark your calendar for June 15th next year and go find and control them.
Getting rid of bagworms:
The simplest method is to remove the bag and the attached silk by hand, then place in a bucket of soapy water to destroy. The effectiveness will depend on the number of bagworms and the willingness of the gardener. The naturalist gardener might consider the balance of predators and benefactors. A type of fly and non-stinging wasp is known to be a predator of bagworm and prefers the daisy and aster family of flowering plants. Strategically, there may be benefit with planting daisys and asters near evergreens to enhance the fly and wasp. Birds! Don’t forget birds as a natural enemy. Woodpeckers and sapsuckers are noted as ones who enjoy the tasty larvae of bagworm. So, including a bird-attracting back yard may also benefit the strategy of a naturalist gardener. The outcome of a naturalist approach will directly relate to the heaviness of the infestation. The goal with nature is balance.
Pesticides remain the preferred method for eliminating bagworms. Applications are advised to begin in May prior to when the eggs hatch and be completed by August prior the larvae reaching maturity. Pesticides work by directly spraying the leaves or by soil application with absorption into the leaves. The leaves are dual purpose for the caterpillar. They are a food source and material for preparing the new bag. Ingesting the pesticide from the leaves kills the caterpillar. Recommended pesticides can be purchased off-shelf from garden centers. Always read and follow all label instructions before using. Be safe!
Send us your questions and comments to the Shelby Purdue Extension Office – 317 392 6460 ext. 0 and https://extension.Purdue.edu/Shelby