Eastern Tent Caterpillars

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Spring is early this year. We know it, the plants know it and guess what? The Eastern Tent Caterpillar knows it too. Eastern tent caterpillars are somewhat hairy and black with gold, white and blue markings. There is a white stripe down the back. The caterpillars grow up to almost 2 inches long and they’re out of their 1” long white/yellow silk cocoons looking for tasty new leaves to eat.

Found throughout eastern North America, you’ll see eastern tent caterpillars on mainly cherry, apple, and crabapple trees, as well as some others. I picked this one up at the gas station, where there were a couple more crawling around on the pavement. I expect they didn’t live long, it was a busy station.

The caterpillars emerge from eggs laid the previous year, and spin a silk webbing in the crotches of tree branches (where the branch meets the trunk, or a small branch meets a larger one). As the caterpillars grow, they will continue to spin the silk webbing around their tent-like nest, adding several layers to expand it’s size. The caterpillars will leave the nest several times a day to look for food on days when the weather is nice, but will return to the nest at night. They feed in groups and may completely strip the new leaves from trees. Trees defoliated for several years by eastern tent caterpillars may weaken.

After about six weeks, the caterpillars leave the web nest and will spin individual cocoons on nearby trees, fence posts, or buildings. Once inside the cocoon, the caterpillar develops into the pupal stage. In early summer, adult moths molt from the pupal stage, emerge and fly away from the cocoons to mate and lay eggs. Caterpillars will emerge from these eggs the following spring in time with the new leaf food sources, and begin the life cycle all over again.

So what about your trees? For the most part, if your trees are mature, the webbed tents are ugly but feeding on the leaves will generally not damage the overall health of the tree unless there are a large number of tents on a single tree, or if the tree is infested repeatedly year after year. Keeping that in mind, how you adress the problem depends on how many caterpillar tents are present and the amount of damage you are willing to put up with.

If there are just a couple, the tents can be pulled down with a stick and the caterpillars crushed or otherwise destroyed. Never use fire to destroy eastern tent caterpillars as fire is extremely dangerous. Fire may damage the tree and endangers the operator and nearby property.

If the problem is more severe, or if the tents are too high to reach with a stick, you can treat with products containing acephate (Orthene), (Orthene TTO), or carbaryl (Sevin), or B.t. (Dipel), or bifenthrin (Talstar). Treat foliage nearest web. It may be difficult to spray branches higher up in the tree, so use caution when spraying. Protect yourself and be sure to read and follow the directions for safe use found on the label of whichever product you are using.

Reminders:

*The Sanford Farmers Market is open for the season. The market will operate on Saturdays, April thru October, 9 a.m. to 12 noon at their new location, the McSwain Extension Education and Agriculture Center and offer locally grown fresh fruits & produce in-season.

*Self Watering Plant Containers workshop Saturday, April 29th. Cost is free, but space is limited. Call 919-775-5624 to register and reserve your place.

Minda Daughtry is Horticulture Agent for North Carolina Cooperative Extension in Lee County.