This story was originally posted on MyNorthwest.com
An invasive bug species, the spongy moth, has been spotted in the tall tree canopies of Lakewood and has the potential to negatively impact Pacific Northwest forests.
The spongy moth can grow up to three inches long, has a hairy body, a small yellow head, and a distinct row of five blue dots followed by six red dots along its back, according to the Washington State Department of Agriculture (WSDA).
“Spongy moth (Lymantria dispar dispar) is a destructive, invasive insect that poses a danger to North America’s forests,” the U.S. Department of Agriculture stated on its website. “Female moths lay eggs on many outdoor surfaces — stacked firewood, trailers, grills, lawn furniture, and toys. When people move these items to a new location, the spongy moth’s eggs also move.”
The spongy moth caterpillars feed on leaves of more than 300 different species of trees and shrubs, which eventually kills them altogether.
“All the damage is done by the caterpillars. The caterpillars eat the leaves, and that’s the biggest problem,” WSDA communications consultant Karla Salp told The News Tribune. “The moths themselves actually don’t eat anything in their adult stage. They just basically mate, and then lay eggs and die. And that’s basically their life cycle over the year. Then those eggs overwinter, and then again, next spring, they’ll hatch out.”
Lakewood plans spring treatment to eradicate species
As the invasive species is generally seen between April and July, the City of Lakewood has scheduled to treat a mile-and-a-half stretch of Lakewood for the species in either April or May.
Salp noted this area will be treated for spongy-moth eradication after WSDA staff located five spongy moths in the area in 2025, and 10 caterpillars the year before.
Although the current number of spongy moths in Lakewood is low, Salp stated that the department’s goal is to eradicate the species while the population remains small, and hopefully find no moths for years, as they have the potential to do extensive damage.
“They have the potential to do widespread damage,” Salp said. “And if that only happens one year, most trees — if they don’t have other stressors — can be resilient and re-leaf. But when you have multiple years of that in a row, as you would in an outbreak, that can actually kill trees.”
Spongy moth caterpillars can also cause rashes in people who come in contact with them. The bugs’ poop is also known to cause car accidents, as the droppings can make the roads slippery in high concentrations.
Over the next month or two, Lakewood residents may see a small plane flying over the town and spraying an insecticide called Bacillus thuringiensis kurstaki (Btk) on the trees below.
Salp noted that Btk contains bacteria that spongy moth caterpillars cannot digest. When the bugs eat foliage that has Btk on it, they will die. Btk also has a very low risk on human health and is not harmful to other insects, such as bees or ants, as well as other animals like birds or fish, according to The News Tribune.
The Btk treatment is used when roughly 40% of leaves have grown on trees, generally the same time as when spongy moth larvae have hatched, and the caterpillars begin feeding on them.
Nearby residents can sign up for alerts announcing when the treatment will begin. If anyone believes they may have spotted a spongy moth caterpillar or moth, they are urged to submit a photo to the WSDA.
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