Fall webworms
Brennan Jackson
County Extension/ANR Agent
One of the more noticeable insects in the fall season are harvestmen (daddy long legs) and fall webworms. In regards to the fall webworm, you have probably seen the white moth which is the adult stage of the webworm and the orange and black larvae with covered in tiny hairs, but the most obvious sign of fall webworms is the web they form. These webs serve to protect the webworms during pupation and provides heat retention. The entire process begins with an adult moth that typically lays around 600 eggs on the underside of a leaf. The eggs hatch after a week or so. Soon after the larvae begin forming their web on the tip of a branch and begin to feed. The webs will typically range in size up to a couple of square feet.
These larvae or caterpillars will feed on leaves which usually result in skeletized leaves within the web.
Unfortunately, fall webworms have a very wide host range and will feed on just about any type of plant. The webs are very obvious while driving down the road and seeing them in trees, but they also affect plants in the landscape as well. The more mature caterpillars will pupate over winter on the ground and the immature caterpillars will pupate in the web. After pupation is complete they will emerge as a white moth.
The damage they cause is aesthetic because they are very unsightly, but they also defoliate the plant that is contained within the web. There are several management options that can be performed to mitigate their damage or presence. The easiest method is to take a pole and penetrate the webbing. This will cause the death of most or all of the caterpillars. In a situation where there is a major infestation, pruning can be done to the infested branches.
Extensive pruning should not be done so as to not negatively affect the tree, but in certain situations it is a good option. There are natural enemies of the webworms including birds, lizards, parasitoids, spiders and insect predators, but their effectiveness will depend on how intensive the infestation. Chemicals can be utilized, but they are really not the best management tool because many times the locations of the webs are not reachable by insecticides.
If there are webworms that are in inaccessible areas, then a trained professional should be contacted.
Insecticides with the active ingredient Bacillus thuringiensis labeled for fall webworms can be used.
For more information, contact the Jones County Extension office at 478-986-3958 or email brennan4@uga.edu.
