Fall Webworm Outbreak

Over the weekend Joe and I were in the eastern Ohio Valley and my goodness did we notice the fall webworm! Seen here nestled in a Sweetgum canopy, it is often found on walnut, hickory, ash, elm, maple and some fruit trees. They are active from July through September and are not to be confused with the Eastern Tent Caterpillar often seen in the spring. We saw huge populations of several nests in single trees. They were very obvious in the landscape, even while driving at 50 mph.

The insect feeds entirely inside its silky nest which it builds in a lush canopy of yummy leaves. The webworm feeds as a 'skeletonizer' on leaves, leaving just a backbone of veins. As food runs out, the caterpillar encases more leaves and the nest grows. There are two generations of webworm per season. The second generation is often more aggressive as the first generation moths lay their eggs and repopulate.

Although unsightly, these pests are often not a serious threat to the overall health of mature shade trees. However, younger trees usually lack the plethora of food reserves and ability to support large populations. Actions to eliminate the nests before they completely defoliate the canopy should be taken. There are many different control methods. If the nest is young and small, an arborist can mechanically prune the nest away. If the nest is very young, a strong shot of water or air may also destroy the pest community. Some chemical controls, such as Bt (Bacillus thuringiensis) or systemic insecticides should be used when multiple nests are located very high in a canopy.

If you know your tree has suffered from the Fall Webworm (or Eastern Tent Caterpillar) in the past keep a good eye on the canopy early in the season. Getting to the nest while it's young and in the first generation is the best cultural control. If you are concerned about the aesthetics or health of your trees as a result of the Fall Webworm, call our office today for a consultation.

895.7000