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Attack of the caterpillars means revenge of the moths

The squirmy eating machines will soon transform into flying egg-laying machines.

Shortly, the pesky tent caterpillars that have covered Kitsap County since early spring are getting ready to begin cocooning and will turn into moths.

“Moths will probably start to emerge beginning in June,” said Peg Tillery, WSU Extension Office horticulture coordinator.

There is still time to rid tent caterpillars right now before they turn into moths. A common chemical used to kill them is Bt (Bacillus thuringiensis) which is applied as a spray. Bt is a live bacterium that acts as stomach poison when eaten by the caterpillars. This works best when the tent caterpillars are small. If the caterpillars are over one inch long or if they are leaving the nests and crawling on the ground, it probably means they are no longer eating and Bt won’t kill them.

“Other chemicals will kill them on contact, but it is very important to read the directions on the label,” Tillery said. “‘The label is the law’ is a common saying here at the WSU Extension Office.”

The tent caterpillar does have a natural enemy, the tachinid fly. Caterpillars with a white egg-shaped spot on their head or back will be taken care of naturally. The white spots are actually the eggs of the tachnid fly. When the eggs hatch, the fly maggots burrow into the caterpillar and begin feasting.

“Recently it seems that nature is really stepping in to reduce the caterpillar population,” said Tillery. “The tachnid flies are laying eggs galore now.”

There are various ways of extracting the caterpillars and their tents without using chemicals, including pruning out the tents and destroying them either by putting the infested branches in a plastic bag and disposing of them in the trash or by burning the tents and caterpillars if you are outside burn ban areas. The best time to prune out the nests is in the early morning or evening when it is cooler and the majority of the caterpillars are in the nests.

Another alternative for roses and berry bushes is to cover them and other small plants with netting.

“The tent caterpillars come in three-year cycles and from what we can tell we are in the third year,” Tillery said. “After this they should be scarce for another three or more years.”

One way to decrease the number of next year’s caterpillars is to dispose of the eggs that the moths lay. The eggs look like styrofoam and are grey or dirty brown. Disposing of the moth cocoons before they hatch also aids in decreasing the caterpillar population for next year. Cocoons are often found in the cracks and crevices in trees and on the siding of houses or in folded leaves.

When the moths appear there are several ways to dispose of them. The moths are naturally attracted to yellow light. One way of keeping them away from your house is to install a white porch light instead of a yellow one. One method commonly used is to kill them is to fill a bucket of water with soap or oil and place the bucket under a yellow light. The moths are drawn to the light’s reflection and will drown in the liquid.

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