Many area trees are becoming a virtual campground for worms.
“What you are seeing this time of year are fall webworms,” said Entomologist Howard Russell of Michigan State University. Entomology is the study of insects and insect larvae.
The webworm has set up camp and their tents are blooming statewide.
In the spring, the silken webbed nests are produced by tent worms, whose life- style and habitat are similar to the fall webworm.
“The difference between the tent worms and the fall webworm is primarily the time of year tenting occurs,” Russell said.
Not to worry about either crawler, because the critters are caterpillars that eat leafy tissue and will not destroy the cell structure of the trees.
Technically, any form of larvae is referred to as a worm, according to Russell.
“They are merely an aesthetic nuisance.”
“Their numbers are up, statewide in the past few years,” said Russell, “but there are no programs to get rid of them because they do not destroy the whole tree.”
Population of the caterpillar fluctuates from year to year, depending on the environmental conditions and predation.
The silky tents made by both the webworm and the tent worm provide housing to thousands of caterpillars, (larvae or worm) during their transformation into moths.
During metamorphisis, the caterpillar passes through as many as 11 phases of growth, devouring different layers of leaf tissue throughout its development.
The fall webworm generally envelops the whole branch on the outside of the tree or landscape plant. Russell said because the entire branch is involved, these caterpillars could potentially do more damage than its spring cousin, however, since the defoliation occurs at the end of the trees’ growth season the trees do not suffer permanent damage.
“It’s late in the season and the trees have already used the leaves,” he confirmed.
Comparatively, the tent worm weaves a nest much smaller than the webworm, adhering it to the crotch or understory of the tree. The reproductive season for the tent worm, however, is in the spring. The devouring of young foliage leaves until the tree is bare during its growing season, could cause permanent damage to the tree.
In the United States both the fall webworm and the tent worm defoliate more than 88 species of trees, scrubs, and ornamentals, yearly. The webworm may also use building walls as hosts.
Russell said if treatment to control the caterpillars is a must because someone absolutely cannot stand the sight of the webbed mangle, natural predators or parasites would be the preferred order of management over pesticides.
While the debate continues over the effect pesticides have on the natural environment, Russell states there are more than 50 species of natural parasites and 36 species of predators to manage the fall webworm.
The entomologist warns, however, that the use of natural predators could cause consequences of an ecological imbalance in the area treated.
“The consideration is the degree of injury to the tree,” warned Russell.
“The more primary consideration here should be the impact the predation could take on both the host tree as well as the tenting caterpillar.”
“The use of natural parasites or predators could take a heavy turn on the tent or fall webworm population, which could cause an ecological imbalance.”
As the webworm “over winters” in the soil around the base of the tree, Russell said it’s better to let nature take it’s course, since little damage is caused to the tree during the metamorphosis of a common moth.