Web Worms: How to Get Rid of the Ugly Pests
Have you noticed giant webs engulfing tips of your tree branches? You may have also noticed the leaves inside the web mess are dead or dying. Your tree has become the new home for a couple hundred web worms. The web worm, also known as Hyphantria cunea, is a moth native to North America. The pale cream colored moth lays it’s eggs in a hairy cluster on the underside of leaves of hardwood trees in the late summer through early fall, laying a few hundred eggs in each cluster. Eggs hatch after about a week and soon the fuzzy yellow larva are busy webbing a cozy home for feasting. This is the stage you typically notice web worms have taken up space on your tree’s limbs. Unfortunately, by this point, your typical pesticides are of no affect. The web actually works as a protective screen from pesticide oils and sprays.
So how do you get rid of these little guys and stop them from eating your tree’s foliage? A quick internet 
search will recommend a pole, blow torch and ladder. Sounds like a hospital visit just waiting to happen, right? Although lighting the web on fire will in fact destroy the web and kill the worms, the obvious variety of dangerous scenarios that might occur after are why we recommend a simpler and safer method.
Here’s what you do:
- Take hand pruners or pole pruners depending on the necessary reach and clip the branch at the point just before the web begins. The foliage within the web is dead anyway so the branch will continue to be unsightly even if the web was removed. Throw the whole branch in the trash or fire pit.
- Spray the remainder of the tree with a Bt Caterpillar Pesticide. You can find a Bt concentrate online here. If the Bt spray is ingested from a coated leaf, the web worm will die within a few days. Bt spray only works during eating season – late summer and fall and will not harm your tree or animals, including birds.
- If you have a hardwood tree that is prone to web worms, coat the tree with a dormant oil during the winter. The dormant oils will kill the web worm in the cocoon stage. Dormant oils can be found at most garden stores.
Problem solved with no fires to put out.
