Fall Webworm Watch

Home Grown  by Keith Reed
We are getting reports in the Extension office of fall webworm activity. While these are common pests, this is a bit more than we normally see. It’s hard to be too bold in predicting the future for insect activity but this is one to keep an eye on right now. This pest is most well-known for the large patches of heavy webbing that can dominate many of our fruit, nut and shade trees.

While webworms are not fatal to a tree, they can be very unsightly and may have a significant impact on fruit and nut production in some years. If potential crop reduction or unsightliness is not a concern, control is unnecessary. However, if you do wish to try to control webworms, scouting now and treating early in the season is the key to success. Once they become well established, it’s too late for spraying to be effective.

Begin scouting by looking for the adult moths. They are pure white and are about 1 1/4” across when their wings are open. Early mornings and late evenings are good times to scout for moth activity with the porch light often being the easiest place to look. Note that all white moths are not webworms. Please don’t panic and rush out and spray just because you see a few, this should only be used to gauge possible activity.

It is the larvae that are the problem with this pest. They are small fuzzy caterpillars that can vary a bit in color but are generally light tan with either brownish-red or black heads. As soon as these larvae hatch and begin feeding, they begin building the web which serves as protection against predators and as it turns out, insecticides.

There are a number of insecticides on the market that will provide good control of these pests when treating early. But as I’ve said, the web acts as an excellent defense mechanism and the web must either be physically disturbed (torn open) or a high pressure sprayer must be used for the insecticides to be effective. Contact the Extension office if you would like suggestions for specific products that are effective in controlling these pests.

Also keep in mind that if you do successfully kill the webworms, the webbing will still be around for the remainder of the season. Physical removal (pruning) is the only safe way to get rid of it. I mention safety because you may hear stories of people who eliminate the webs by burning them out. I’ve seen this go badly too many times to suggest it. It is not worth risking getting someone burned or starting a fire just to eliminate some unsightliness.


For more information of this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at keith.reed@okstate.edu, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.

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