Last week we found an
egg mass of the fall webworm. This week we found hatched out larvae feeding comfortably in their loosely spun web (photo at right). Just like
newly hatched walnut caterpillars, first instar fall webworms do not have large enough mouth parts to bite through an entire pecan leaf. Instead these young larvae just scrape off the outer layer of cells on both sides of the leaf. In the photo, the leaflets nearest to the cluster of caterpillars has just been scraped clean of its outer layer. As these leaflets dry, they will turn brown just like the other leaflets under the web.
We are not finding a large number of first summer generation webworm colonies at this time. However, since it looks like we are facing a walnut caterpillar outbreak this summer, insecticides applied to control walnut caterpillar will also control fall webworm.
