Renee the caterpillars you found are the larvae, caterpillars of the Black Headed Fall Webworm. The Fall Webworm (Hyphantria cunea) has two generations per season in Ohio. The “fall” in the webworm’s common name is based on the appearance of second generation nests late in the season. The Fall Webworm are primarily a nuisance for trees and don't pose a significant threat to people or healthy trees. However, young trees or unhealthy trees can be impacted by heavy infestations. And people with sensitive skin, who come into contact with the worms, may develop a skin irritation because of the long hairs on the caterpillars.

  You can reduce their numbers by destroying their webs using a stick or broom for webs within reach or a stream of water for webs higher up. Except for situations of heavy infestations chemical controls are not recommended.  If you do use chemical controls be sure to read and follow the directions on the label.

  Thanks for using Ask a Master Gardener and thanks for the photos, they were a big help. Here are links to two factsheet with more information on the Fall Webworm.

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