The annual outbreak of fall webworms is now occurring in the Oklahoma area, and appears to be more severe compared to the previous few years. This is probably due to the increased rain and denser foliage on trees. Webs can be seen in many ornamental trees, especially in pecan, hickory, persimmon, sweetgum, willow, redbud, oaks, and in many fruit trees. The webs are formed from masses of small caterpillars inside the web as they are feeding on the tree leaves. After the larva hatch they pupate in the back and ground under the tree, hatching into tiny white moths later in the season or the following spring. The moths then lay their eggs mainly on the underneath side of these deciduous trees which they prefer, and hatch into larva a few weeks later, completing the cycle.
In Oklahoma, two generations are often seen, so expect another round of webworm infestation later in summer or early fall. Often this second generation is more severe than the first one. The small webworm caterpillars are about 1” long with tiny gray hairs. As they feed inside the silken mass, they expand into the tree foliage, destroying the leaves as they go. They usually don’t cause much actual damage to trees, but the webs and caterpillars inside are ugly, and homeowners don’t like to see them eating up their tree leaves.
By the time webs are seen, it’s very difficult to control the webworms. If webs can be reached from the ground or with a pole, simply break up the web and destroy the webworms. Use a high pressure hose to spray into the web to try to break it up and knock the worms out of the tree. Applying insecticides can be used, and LawnAmerica does provide this service, but we really don’t recommend it that often. The spray has to penetrate the web mass to be most effective, and by the time the webs form, the webworms are at the end of their life cycle. If you have trees such as pecan, hickory, and persimmon which are very susceptible to webworm damage every season, it’s best to apply a preventative insecticide treatment earlier in the spring before they begin feeding and building their webs.
In most cases, it’s really best to just not worry too much with the webs which cannot be knocked out of the tree. They really don’t affect the health of the tree that much. Even if they defoliate a good portion of the tree, the tree will not die, unless other issues are present or this problem occurs year after year. So we encourage our customers to use discretion when deciding upon an insecticide treatment or not. Having us apply will help somewhat with the spread of the worms, but will not make the existing webs go away, as they will need to just eventually blow away, which they will.