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Fall Webworm

FALL WEBWORM
By Bailey Walten 1990 Newsletter

Last Summer and Early Fall brought the heaviest, wide-spread outbreak of “fall webworm”, Hyphantia cunea, we have seen in our area. This species of tigermoth attacks up to 120 varieties of fruit and shade trees as well as various ornamental shrubs. It should not be confused with Eastern Tent Caterpillar whose primary diet is “fruit trees” in the early Spring.

The adult is white with a few dark spots and the larva (caterpillar stage) is pale yellow or green with long light gray hairs and two rows of black spots running the length of its back. Native to North America, this insect has two generations per year. The first generation begins hatching in late May through June while the later generation, and most destructive, appears in late July through September. Upon hatching, the young larvae immediately spin webs around the tips of branches and begin feeding on the leaves within their newly spun web. As they run out of food (foliage) they increase the size of their web, often encasing entire limbs, and in some cases entire trees with their unsightly web.

Since most of the damage caused by the fall webworm occurs in the late Summer and early Fall, after trees have produced their primary food reserves through photosynthesis, they are not nearly as detrimental as early season pests. Because of this, they are considered more of a nuisance pest with its extensive webbing and dirty droppings.

The fall webworm can be successfully controlled by spraying after they hatch and are feeding. Contrary to some thoughts, spraying is warranted when outbreaks occur early in the season to eliminate damage to the foliage as well as reduce next years’ population