By Stephanie Butcher, Coweta County Extension Office

Question: Webs are covering my pecan tree in my backyard? What are they and will they kill my tree?

Agent:   Two types of caterpillars make webs in trees – the Eastern tent caterpillar makes their webs in the forks of the branches and are more of a problem in the spring, but fall webworms make their webs on the ends of the branches. They are more noticeable and they are the ones you are seeing right now.

Fall webworms will feed on the leaves of more than 100 types of trees, but they prefer pecan, black walnut, oak, sweetgum, and other ornamental trees. I see them most often in pecan trees though.

The caterpillars form fine silken webs on the ends of the branches. They will enlarge the webs if they need more leaves. They feed on the leaves in these webs for a couple of weeks before they leave the trees to become pupae. These pupae eventually turn into white moths that will fly away to lay eggs on trees to start another generation of webworms. There can be up to four generations of fall webworms in a year.

Healthy trees are able to withstand a great deal of insect damage to their leaves without lasting injury. I would not be concerned about insects feeding on healthy trees unless most of the leaves were gone. If trees are not healthy, then a webworm infestation may damage or kill the tree over time, but that is rare.

Think about it. It won’t be long before these trees lose their leaves in the fall anyway. This is true of most deciduous trees (trees that lose their leaves in the fall) but not needled, evergreen trees like pines, cedars, junipers and other conifers. Evergreen trees with needles cannot withstand the loss of their leaves and must be better protected against loss of leaves. Fortunately, webworms do not like to attack needled evergreen trees.

Since most trees will not die from caterpillar attack, I do not recommend spraying or other methods of control. If you just leave them alone, they will eventually leave or their natural predators (birds, parasitic insects, etc.) will take care of them for you.

Fall webworms also have a neat habit that is interesting. When disturbed, all of the caterpillars in a nest will make a distinctive “jerk” in perfect rhythm. Tap branches near their web or make a loud noise by clapping your hands or shouting and you’ll get to see it! They do this to help scare away predators.

For more information about fall webworms, contact the Coweta County Extension office at 770-254-2620 or [email protected].
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