Fall Webworm Caterpillars 101

You may have noticed swaths of white webbing covering probably the majority of trees and bushes in your yard. They seem to appear overnight, marking the end of summer and descent into fall. But what creates these webs and why? It’s the Fall Webworm.

The Fall Webworm

The critters behind the tangled mess in your yard are called Fall Webworms aka Hyphantria cuneaIn the fall (hence the name), these ugly, furry, spiky caterpillar eventually morph into a moth that thrives during the summer months. The eggs are quite small, roughly .5mm, pale green or yellow. The larva are usually yellow, striped, covered in hair, and normally an inch long, according to the Tree Fruit Research & Extension Center at Washington State University.

Fall Webworm

Fall Webworm

The caterpillars remain encapsulated in the web they’ve woven at the tips of branches, rather than at tree crotches like their northern cousin. Fall Webworms feed on the leaves of basically every type of deciduous tree (ones with leaves that fall annually); their favorites are “mulberry, walnut, hickory, elm, sweetgum, poplar, willow, oak, linden, ash, apple, and other fruit trees.” As they eat all they can from one branch, the Fall Webworm expands its reach to the nearest food source. If you’ve ever wondered what’s inside these expanses of sticky web, it’s a mixture of caterpillars, dead leaves, and fecal droppings, according to the Department of Entomology at Pennsylvania State University. Lastly, the moths stay generally just as small, with a wingspan of roughly one inch. In the South, the moths are white with brown spots.

Where They Are Besides Savannah

The Fall Webworms have invaded all of North America and made their way to Europe and Asia as well. They’ve been a menace since the 1940s. There is good news, though! First, the maturation period is about six weeks. Secondly, despite being a visual nuisance, they don’t cause any physical harm to people nor do they cause any lasting damage to the vegetation they inhabit and feed from.

Interestingly enough: If the caterpillars feel threatened, they will all make a jerking motion, which rocks the entire nest, as a defensive mechanism.

Pest Control

Perhaps the best news of all is that there are a few different ways to eliminate and control the Fall Webworm population in your yard.

  •       You can simply remove the webbing from the branches and bushes then destroy them by burning or freezing.
  •       You can open the nests and allow their (numerous) natural predators to do the dirty work. Predators include yellow jackets, wasps, and birds.
  •       Plant predator-attacking flowers and plants around your yard to discourage Fall Webworms from making your home their home. Like in the last suggestion, the predators will deal with the caterpillars, as their webs aren’t secure or all that safe.
  •       You could also spray a bit of insecticide on the webs. No need to use a copious amount because the caterpillars will come across whatever your spray as they move about the nest.
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Don’t forget, warm weather is leaving us but not all of your pests are leaving with it. Colder weather means many pests look for harbor in warm and dry places including rodents.  We’re ready and available to help alleviate any pest issues you’re having!

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