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Bagworms and tent caterpillars are often confused with each other (GoodSeed Nursery photo)

Steve Boehme

Suddenly it’s spring and you can see tent caterpillars everywhere. Bagworms aren’t as visible, but they’re emerging too. People often confuse these two pests, so let’s make sure we’re talking about the right one.

Tent caterpillars are easy to spot because they make large white nests in the forks and crotches of trees. They are particularly fond of wild cherry trees, but you’ll see them in other ornamental fruit trees like purple plum and crabapple, and in orchard trees. Their web-like “tents” protect the caterpillars from sprays and predators.

Bagworms create camouflaged homes for themselves out of leaves and evergreen needles, which they carry around on their backs. These shelters get larger and larger as the worms grow, and they protect the worms from sprays and predators. Bagworms are tiny right now, and by the time you can see them they will be very hard to control.

Bagworms are best known for attacking evergreens like arborvitae, pine, spruce and Eastern red cedar. They also eat barberry, blackberry, box elder, cherry, clematis, elm, locust, maple, oak, peach, poplar, pyracantha, rose, sumac, sycamore and willow. If necessary, bagworms will even feed on clover, ragweed, parsley and nightshade

Baby bagworms are about the size of the point on a sharpened pencil lead, he said. They start feeding as soon as they hatch, and they quickly start growing and spinning silken bags around their bodies for protection. Spraying is most effective in early spring when they’re too small to see with the naked eye. The longer you wait after that, the bigger the bagworms and their damage will be, and, the more protection their bag will provide. By late summer, a mature bag actually repels pesticide sprays. There are many sprays and chemicals to control tent caterpillars and bagworms, and most of them work on both if your timing is right. Organic options include Bacillus thuringiensis (also called BT) and spinosad. Chemical controls are acephate, bifenthrin, carbaryl, cyfluthrin, cyhalothrin, malathion, or permethrin. All of these controls work by poisoning the plant leaves, so that bagworms or tent caterpillars are poisoned when they eat your plants.

Our favorite control for bagworms and tent caterpillars is “Captain Jack’s Deadbug Brew” from Bonide. This is a good all-purpose insecticide that works on many other garden pests, and it is an OMRI-approved organic remedy. We’ve used BT (Bacillus thuringiensis) successfully, too. We carry both in our garden center. Simply spray the entire plant thoroughly, wetting all the leaves, in early spring, and again when the leaves are fully open. The sprays work by ruining the bagworm or tent caterpillars’ appetite, causing them to starve.

Steve Boehme and his wife Marjorie own GoodSeed Nursery & Landscape, located at 9736 Tri-County Highway, near Winchester, Ohio. More information is available at www.goodseedfarm.com or call (937) 587-7021.

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