When I was a kid living in the hills of West Virginia, I was fascinated by white, fluffy masses that appeared in the trees every spring. To this sugar-deprived 7 year old, the fluffy masses looked like cotton candy – until I got close enough to see the caterpillars. The silken tents, which are sometimes referred to as nests, were created by the larvae of the Eastern tent caterpillar, a North American native.

As far as insects go, the Eastern tent caterpillar is fairly attractive. But its appetite for trees makes it a formidable foe.

Photo Credit: ©2007 Buglady Consulting

In springtime, the caterpillars build their fluffy tents in tree crotches for protection against the weather and predators. They particularly like to feed on flowering fruit trees.

Photo Credit: ©2007 Buglady Consulting

While Eastern tent caterpillars don’t typically kill a tree in one season, they can certainly make them look unsightly.

Photo Credit: ©2007 Buglady Consulting

The Eastern tent caterpillar is widely distributed east of the Rocky Mountains, and they’re most commonly found on wild cherry, apple and crabapple trees. But these pests may also be found on peach, oak, ash, birch, poplar, hawthorn, maple, cherry, plum and pear trees.

It’s the small trees like these that are most susceptible to defoliation by Eastern tent caterpillars. While defoliation in one season doesn’t kill the tree, it increases stress levels, which raises susceptibility to other pests and diseases. In your yard, the tents and defoliation caused by caterpillars reduce the aesthetic value of your trees. Despite the damage these pests cause, most people in urban and suburban areas are basically just “grossed out” by the masses of caterpillars as they wander from the trees across patios, sidewalks and drives in search of a place to rest and change into a moth.

Fortunately, there is only one generation of these pests a year. Eastern tent caterpillars spend the winter as eggs laid by females the summer before. The eggs are laid in a group that typically encircles smaller twigs. In spring, the eggs hatch about the time that tree buds break. The larvae remain together in a group building a small tent made of silk produced by their salivary glands. The tents are built in tree crotches because the structure helps to protect the caterpillars from predators and adverse weather. During cooler times of the day, the crawlers leave the tent in search of leaves to eat, and they return when the temperature is too warm or it rains. This goes on for up to six weeks – until the caterpillars leave the tent in search of a place to pupate. Moths emerge midsummer and lay eggs after mating.

As far as caterpillars go, these ones are rather attractive. They’re dark-colored and hairy with a white dorsal stripe. Yellowish or brown lines stretch the sides of their bodies, along with bright blue spots. They grow to be 2 to 2 ½ inches long.

Now that you know what they look like and how they grow, what about controlling Eastern tent caterpillars? Well, there are several methods. The good thing is that due to the caterpillars’ rather prominent appearance, it’s easy to spot infestations. Keeping this in mind, probably the simplest strategy is to destroy either the egg masses or the tents. In fall, egg masses are easy to spot in landscape trees – they’re dark and encircle small twigs. If you find them, simply clip them off or crush the eggs. If you don’t find any egg masses but do find tents in spring, just trim those out of the tree and destroy them. I have witnessed a neighbor actually take a vacuum cleaner to a tent to remove all the caterpillars.

Another control option is to spray the foliage of trees you want to protect with Bacillus thuringiensis (Bt) formulations. It’s best to treat the trees when the larvae are small. A final option may include insecticide application. Spray the tent and surrounding foliage. Please be sure to consult your local extension office for spray recommendations.

Eastern tent caterpillars are beautiful – and even tempting for sugar-hungry kids – but they can be damaging. The fact is little can be done to prevent them from infesting your landscape if eggs aren’t found and removed before spring. But the good news is that the tents they build are easily noticed and can be removed or treated before substantial damage occurs. So keep your eyes to the sky this spring and watch out for the tents.

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