There is nothing better than a pie made using pecans harvested from a tree in Pontotoc County. You may have visited your favorite tree recently with hopes of finding a large crop of developing pecans only to see large webs filled with worms. This discovery could be a problem for the main ingredient in your homemade pecan pie.
The webs often found in pecan trees are produced by fall webworms. This pest primarily attacks pecan but other trees including persimmon, sweet gum, and Bradford pear can also be hosts. I will give a description of fall webworms and give control recommendations. The sources for this article include the Mississippi State University Extension Service publications, “Insect Pests of Ornamental Plants in the Home Landscape” and the “Bugs Eye View” newsletter written by Dr. Blake Layton entitled “Fall Webworm”.
The formation of the unsightly webs often found in pecan and other hardwood trees begins when female fall webworm moths lay a mass of pale green eggs on the undersides of the leaves. Upon hatching, the webworm caterpillars begin building the web around themselves and the leaves that will be their food source. The web will serve as a barrier that will protect the webworms from predators including birds, wasps, yellow jackets, and parasites.
The physical appearance of fall webworms can vary. Some specimens have red heads with light-colored spots while others can have black heads and dark spots. All specimens will have long light-colored hairs on their bodies. Fall webworms will grow to around one inch in length. While there are two generations of these insects each year, fall webworms are most common in late summer and into the fall.
Fall webworms will expand their webs to include more leaves as they grow. When the webworms near maturity they will exit the webs at night to feed. On years of heavy infestations some trees can be completely defoliated. Large heathy trees can recover, but the result will be poorly filled pecans and very few pecans the following year.
Commercial pecan operations can easily treat fall webworms with specialized spray equipment and effective insecticides. Treatment is more difficult for homeowners without these weapons in their arsenal.
Homeowners can treat fall webworms with insecticides containing the active ingredient spinosad. Trees that are less than 20 feet tall can be sprayed using a garden hose sprayer attachment or another type of sprayer that can reach the top of the tree.
Homeowners with larger trees can choose to get more creative. It is possible to use a long pole fashioned with a hook on the end to rip the webs open. This allows predators to feed on the exposed caterpillars. Homeowners with very large trees may decide that the do-nothing approach is the most reasonable treatment choice since it can be very difficult to treat the entire tree.
Good luck! I hope your trees will be free of fall webworms and produce all the pecans needed for a delicious pie!