Fall Webworm

Webworm is a garden pest that hangs out in a huge community and is sometimes confused with the Tent Caterpillar..

They are easily spotted in your trees after they have started spinning their webs.

The yellow arrows are pointing to the webs that appeared in my Redbud tree. While I couldn't get close enough to show you their webs while in the tree, I did manage to trim out the branches. Trimming out the branches allowed me to grab some close up photos of the webs and the worms inside of them.

Insect Facts

Webworms create web like nests at the tips of branches. Typically webs are seen in late summer through fall. The webs can cover an area about a foot or longer.
Tent Caterpillars (not shown on this page) create webs in the crotch area of branches. They don't go out to the tips.

As you can see these are a creamy white color with a black head and dots down their sides. They are about 3/4 to 1 inch long.

There is also another variety that can have the white bodies and black dots but with red heads.

Life Cycle:
Eggs are deposited on the bottom of leaves. The eggs hatch in 7-10 days. The mass of tiny caterpillars then form a web around their community to protect themselves. At first they will eat the fleshy part of the leaves leaving the veins.(see picture below for an example of a skeletized leaf.) As they get stronger they'll eat the whole leaf. If the food supply runs low they expand their webbing. The caterpillar (larvae) mature in four to six weeks. Once mature they drop to the ground and pupate into moths. The moths lay the eggs on the underside of leaves and the whole process starts again.

In Northern areas you can have two generations in one year. In Southern areas you can have up to four per year.

The yellow arrow shows a partially skeletized leaf where they were eating the fleshy part and leaving the veins.

Damage

Even though there seems to be a lot of webworms it would take many more of them and several consecutive years of attacks to do major damage to the tree.

Webworms don't typically kill a tree. The webs look unsightly, the worms are creepy but eating leaves in the fall isn't as bad for your tree as if they ate them in the spring. The leaves on a tree have finished their major work by the end of July early August. Any leaves lost after that time shouldn't create any major decline in your trees overall health. (the leaves are going to start falling in a month or two anyway!)

Garden Pest Control

I put a couple drops of dish liquid into the bucket and filled it with water.
I cut the branches so that no part of them stuck too far out of the water. I made two buckets of the soapy water mixture to fit all the webs into. I let them sit overnight and then dumped them out.

Problem solved for this year.

Chemical control may be needed if the webs are too high up in the tree for you to reach them or if there are so many of them that cutting them out would destroy the shape of the tree.

Wear eye protection when spraying into trees.
Spray the web and the surrounding leaves with your chosen insecticide. The webs will not fall out of the tree so in a week or two you can try knocking them out with a jet of water. At that time you can check the nests to see if there are any surviving webworms or if there are any new nests. If there are some still alive then you will want to spray again.

If the trees containing the worms are too tall for spraying a systemic insecticide can be used. Systemic insecticides are feed into the root system of the tree or injected into the trunk. The chemical will then travel up through the trunk and out into the branches and leaves where it will be ingested by the webworms. Timing is important in using systemic insecticides as it takes time for the chemicals to get absorbed and travel up to the leaves.

Return to the Insect page from this Webworm page.

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