Webworms make trees messy

This seems to be a big year for fall web­worms, the insects or caterpillars that make their webs at the end of branches on trees such as pecan, hickory, persimmon, sycamore, black cherry, sweet gum, river birch and Chinese elm.


They particularly like pecan trees. I have seen some covered by webs like never before.

As always, the number of these pests fluctuates. This is mainly from the populations of predators that feed on them, and winter temperatures. We certainly didn’t have much of a winter.

Some people mistakenly call these tent caterpillars, but tent caterpillars build webs in the fork of a tree and occur in spring or early summer. Webworms come later in the summer and are at the ends of the branches.

The adult stage of a webworm is a white moth about 11/4-inches long. Sometimes the forewing is marked with blackish dots. Moths of the first generation emerge from May to July and the second generation comes in July and August. This explains why they last so long. The adult female lays 400-500 eggs in white, cottony patches on the underside of leaves and plants.

After the eggs are laid, they hatch in about a week. The larvae form a web and begin to skeletonize the leaves by feeding in rows. As the larvae grow, they expand the web to cover the colony. They eat only the leaves inside the web.

When the larvae are ready to pupate, they crawl or drop to the ground and form a brownish cocoon in the duff around the tree, where they overwinter.

I have been asked before if treating the ground will stop them for the next year. Most likely not, because unless everybody who lives near you also does it, the moths will just fly back over into your trees. But webworms do have natural enemies to help keep them under control.

Webworm damage is mainly cosmetic, but many people want to control them. Control measures depend on a few circumstances. If your tree is large and the webs are high up, it makes spraying with an insecticide practically impossible. If you can reach the webs with a high-pressure nozzle to just blast water, you can knock many of the caterpillars out of the tree. The blast also breaks up the web, allowing birds to eat the webworms. Wasps also prey on the caterpillars.

If you can reach the webs with a hose end sprayer, any insecticide will kill them. Good choices are carbaryl (Sevin), malathion, acephate, Bt. Pro­ducts (organic), bifenthrin, lamda-cyhalothrin or cyfluthrin. Make sure you penetrate the web when spraying.

The good news is that trees will not die from the webworms. They just look unsightly. Don’t worry, when the webworms leave the web to pupate in the ground, they are not looking for anything else to eat in your landscape.

Your e-mails

As you can imagine, I get a lot of e-mail questions about problems.

When writing to me, try to include as much information as you can. Pictures are a tremendous help. Many questions I get are so vague I have to try and guess what people are talking about.

For example, if you have insect problems, try to be specific as to what they look like and what plants they are feeding on.

Another example of being vague is when someone asks, “What is a good hedge to plant?” Specifics that would help include what type of exposure (sun/shade) and the size you would like. There is a big difference between a 6-foot hedge and a 15-foot hedge.

I also get asked about certain things I write about that might apply only to our area. Since many of my articles are found on the Web, I get questions from all over the country – even from outside the U.S.

Identify where you’re from because some of what I write about might not be applicable to where you live.

Someone from outside the Augusta area may write and ask me where to buy something I mentioned.

For example, a few years ago I wrote about the new TifGrand bermudagrass. I got numerous e-mails from people in the Atlanta area asking me where they could buy it near where they live. I am sorry, but I just don’t know. I usually tell them to contact the extension agent in their county.

One of my favorites questions is when people say, “I enjoyed reading your column on …” Then they proceed to ask me a question that was answered in the column. What I would like to say back is, “Well if you truly read it, you wouldn’t be asking me that!”

On a side note: In spite of showing my name Sid Mullis by my picture and listing my e-mail as smullis@uga.edu, many times the salutation is “Dear Mr. Mullins!”

Keep ’em coming!