Driving down the highway you’ll see numerous webs up in trees all created by Fall webworm larvae.
These caterpillars are general leaf feeders that colonize numerous hardwood tree species including pecan, hickory, black walnut, persimmon, and green ash. If you get up close to one the the dirty white webs, you will note that all the foliage inside the web has been devoured by the caterpillars (photo above). Leaves outside the web are still green and untouched.
By late July, all of the webs have been vacated. A closer look into the web will reveal nothing but the white fuzzy exoskeletons discarded by molting caterpillars and black balls of insect frass (photo at left). Once the caterpillars reach maturity, they drop out of the web and settle down in the leaf litter on the ground. The caterpillars then spin a cocoon to begin the process of changing into an adult moth.
At this point in time we are between generations. The second summer flight of fall webworm moths usually starts in early to mid-August. Judging from the number of first generation colonies I’ve seen up and down the road, the second generation should be ever larger. Fortunately, we will be spraying our trees for stinkbugs and pecan weevils during the month of August and these sprays will keep the second generation out of our pecan grove.