Friday, April 25, 2014
This time of year the South Carolina Forestry Commission gets calls from spooked homeowners wondering just what’s spinning the large web-like sacks on trees in their yards.
To the uninitiated, this web mass evokes thoughts of spiders and sends many straight to the garden center at the hardware store to arm themselves with pesticides and heavy gloves. But the fear is unwarranted. The eastern tent caterpillar is merely making itself a screened-in porch where it will munch on leaves to “carb-up” before pupating into its moth form.
Trouble is it prefers many homeowners’ most loved trees on their property. The white, silken tents are popping up in the branch crotches of cherry, crab apple, and apple trees.
These caterpillars can sometimes be found on ash, birch, black gum (aka black Tupelo), willow, witch-hazel, maple, oaks, poplar, peach and plum trees, although cherry trees are their preferred place to set up camp.
Daring explorers can poke inside to see this caterpillar with its long brown hairs, and white stripe on the back bordered by yellow-brown and black lines. You’ll notice too the blue and black spots on the sides of the little caterpillars. While these caterpillars do not have stinging hairs, the hair can cause skin irritation to some people.
There is only one generation (egg- caterpillar- pupa- adult) per year. Each summer, the adult female moth will lay 100 to 300 eggs in a dark brown varnish-like egg mass around a small twig, probably in June or July. The caterpillars don’t hatch from the eggs until the following spring, typically in March or April when the cherry buds are breaking.
After hatching, the caterpillars collectively make the tent that we notice this time of year. They’ll leave their tent to begin feeding on the newly emerging leaves.
After four-to-six weeks, the fully-grown caterpillars will leave the nest for a final time to find a protected place to make their cocoons (pupate). You may even see large numbers of caterpillars walking across your deck or driveway. In early summer, the light brown adult moths emerge from the cocoons (May/July). After mating, the female will lay eggs and the cycle will begin again.
There is little to no damage to the trees since they’ll simply replace the leaves the caterpillars ate. If the homeowner finds the webs offensive or annoying, the tent can be destroyed with a stick. However, if you kind of like the “haunted house” ambiance, leave them there.
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