Tent caterpillars, or army worms, have returned to the Northeast with a vengeance. Many people are defending their trees from the caterpillars, who defoliate an area completely before moving on to the next stand.
Several home remedies have been created, but Marylee McArthur said some are more effective than others – and less harmful to birds and bees. McArthur is the Garden Line Co-ordinator at the University of Saskatchewan.
“What Garden Line usually recommends is Btk. It’s a biological insecticide. That means it’s not as toxic and can be used on all types of caterpillars: cabbage worms, horn worms, tent caterpillars, gypsy moths, and others. It’s used on fruit trees, shade trees, ornamentals, and evergreens,” McArthur explained.
She warned against the use of Malathion, which can hurt several levels of the food chain, including bees and birds. McArthur said a homemade concoction of soap, water, and cooking oil would work as a non-toxic insecticidal soap.
Some gardeners have tried wrapping their trees with tinfoil or sticky tape, but McArthur said that method wasn’t recommended.
As for those who prefer to leave the caterpillars be:
“[After defoliation], the tree will put out its energy to a new flush of leaves. But to do that three years in a row, it would be putting a lot of stress on the tree,” explained McArthur. “They could die if they’re defoliated three times.”
McArthur said the tent caterpillars tend to follow a pattern of three years on, ten years off. She believed they were into their third year of being ‘on’. For those afflicted by tent caterpillars, relief may come next year.