Caterpillars such as webworms, tent caterpillars and bagworms can invade trees throughout the year. The biggest threat they cause is defoliation as they eat tree leaves. Although a number of insecticides on the market can remedy an infestation, tree caterpillars are often quickly and efficiently disposed of by natural methods.

Removing by Hand

If small trees have just a few caterpillars, the simplest method of removing the caterpillars is to pluck off the pests by hand. You can mash them between your fingers or step on them to kill them, but that is not a job for a person with a weak stomach. A much cleaner option is to drop the caterpillars in a bucket of soapy water. The pests will die on contact with the solution.

Destroying Nests

Tree caterpillar nests look like silken bags hanging in branches. You can either remove each nest by cutting the silken string at its top and then dropping the entire nest in soapy water or tear the nest open with a stick and let birds prey on the caterpillars inside. The pests feed during the day when the sun shines. So remove nests at dusk, at dawn or on cloudy days after the caterpillars return to them.

Preventing Attacks

Wrapping a barrier around each tree’s trunk and coating the barrier prevents caterpillars from attacking the trees. Wrap a band of tin foil, tar paper or duct tape completely around each tree’s trunk, and coat each barrier with petroleum jelly. Caterpillars cannot crawl across the coated barriers. Reapply petroleum jelly as needed, and avoid getting it directly on the trees because it could damage the bark.

Helping Damaged Trees

Trees that suffered a caterpillar infestation need special care. Keep defoliated trees watered. They need at least 1 inch of water from rain and/or irrigation per week from May through September. Also avoid using fertilizers and weed-and-feed products that put additional stress on the trees as they work to produce foliage. Because damaged trees often are targeted by pests and diseases, inspect your trees regularly so you can identify problems and treat them before they cause additional damage.

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