What IS that? What You Need to Know about Webworms

Have you recently noticed what look like spider webs wrapped around the ends of tree branches and wondered just what the heck they are (aside from gross)?

Are they killing the trees? Taking over the world? Well, I’m here to ease your anxieties and equip you with the knowledge needed to combat your web-based fears.

The silk bags you see on the ends of the tree branches belong to the larva of fall webworms, not to be confused with bagworms or Eastern tent caterpillars.

Bagworms attach their cocoons to twigs and small branches and are very easy to remove although harder to see. Eastern tent larvae form their silk “bags” in the forks of tree branches rather than the tips, and are active in the spring rather than summer and fall. 

Fall webworms are moths native to North America but have spread nearly worldwide after their inadvertent introduction to Yugoslavia and the rest of Europe during World War II (American imperialism, am I right?).

There are two distinct types of webworm, the black-headed and the orange-headed. The main difference between these two, aside from the obvious color differences, is that the black-headed ones lay their eggs earlier in the season so they are able to fit two generations into a single year while the orange-headed one fits in only a single generation per year. 


The female moths lay their eggs in June, then about two to three months later the eggs hatch and the larvae emerge. They spin their web, and feed only on the leaves within the web’s confines.

As the larvae grow, they increase the size of the web and continue to stay within its protective boundary. The web will take on a rather dirty appearance as it is filled with frass (insect poop) and shed skin from the growing larvae.

Towards the end of their four to six week confinement/larval stage, they will begin to leave the web at night to search for food. When they are ready to enter their final stage of development, the pupal stage, they will leave the web one final time and find a nice dark place to hide, like a pile of leaves at the base of the tree. Here they will spin their cocoon.


As unsightly as the webs are in the summer and fall, it may come as a surprise to learn that the damage fall webworms cause to trees is actually negligible and pretty much only aesthetic.

They only feed on/live in deciduous trees (the trees that lose their leaves each winter) and not conifers (evergreens). This means that since they feed towards the end of the season when the trees are already preparing to lose their leaves, the damage caused by the feasting larvae is really only aesthetic. The trees appear to be unimpacted the following year and grow like normal. 

Trees that are already weak may take the hit of decreased photosynthesis harder, especially if they become fully infested multiple years in a row. A healthy tree is not going to be impacted negatively outside of not winning any beauty contests that year.


If you decide you want to remove the unsightly webs, there are a couple of ways to do that without the use of chemicals. If you would like to go a chemical route, you can look up the different options available to you. Just make sure to follow all safety guidelines to protect yourself and the environment. 

“I’m gonna wash those caterpillars right out of my leaves,” said to the tune of the South Pacific song, which is the first method you can utilize. Simply dunk and hold the web mass in a bucket of soapy water with it either still attached to the tree, or after cutting it from the tree branch. The soap helps increase the surface tension of the water so it’s harder for the caterpillars to escape drowning. You can also simply cut off the offending area and burn it, or toss it in your least favorite neighbor’s yard for them to deal with. 

Another method is to actually break apart the web, exposing the caterpillars to the outside world where they will be enjoyed by the local birds, wasps, and other parasitic insects. Oftentimes if you have a healthy, balanced local ecosystem, other creatures will take care of the problem for you without you needing to become involved. Nature is so cool!

Just be mindful about wearing gloves during this process since some people are sensitive to the caterpillars’ quills. Another thing to be aware of is that when the caterpillars feel threatened, they will actually start to wiggle en masse, making the entire web bounce and shake. It is thought that this dance party is a defense mechanism to help protect them against predation.

Final thoughts

So if you see webs wrapping the ends of tree branches later in the season, be not afraid! They are the harmless, seasonal homes of the humble, world dominating webworm moth.

Webs seen in the spring belong to Eastern tent caterpillars and occur at the fork of a tree branch rather than the branch tips. Oftentimes if you have a healthy ecosystem, the caterpillars will be removed through predation and you will not need to worry about them. 



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