Courtesy Washington State Department of Agriculture
The Washington State Department of Agriculture found more than 90 female gypsy moths laying eggs outside a Puyallup, Wash., home this month, averting what the department said could have been a long and expensive campaign to stop an infestation of the leaf-eating pest.
WSDA Pest Program Manager Jim Marra called the find extraordinary. The department has been on-guard for gypsy moths for more than 40 years, but had never spotted females in the act of laying hard-to-detect egg masses.
“To halt the egg-laying activity and remove this infestation before the caterpillars hatched likely saved our state from an extensive, multi-year eradication project that would have cost millions of dollars,” he said.
WSDA routinely traps male gypsy moths, which fly into baited cardboard enclosures. European female gypsy moths, however, can’t fly and are hidden while each lays ups to 1,000 eggs. The caterpillars in the spring are highly destructive and feed on more than 300 species of trees and shrubs, according to the USDA.
Gypsy moths are entrenched in many counties in the East and Midwest, where the USDA enforces a quarantine to keep the pest from spreading. So far, the USDA and state agriculture departments have kept gypsy moths from being established west of Wisconsin.
WSDA this summer put out nearly 30,000 scented gypsy moth traps statewide. As of Tuesday, 91 gypsy moths had been trapped, including more than 80 in Puyallup and Graham. WSDA put out a large number of traps in the neighboring Pierce County communities because two moths were caught there last summer.
The mass capture this year caused WSDA to begin searching for egg masses Aug. 1. Environmental education specialist Karla Salp checked an ornamental plum tree where a male moth had been trapped and uncovered the female moths laying eggs in a bush growing against the tree.
“That was a pretty astounding thing to find,” she said.
WSDA checked the neighborhood but found no other female moths, Salp said.
WSDA removed the bush and egg masses. The residence is owned by a rental company and was vacant, Salp said.
The department probably will spray the area with a pesticide in the spring to kill emerging caterpillars, Salp said. Usually, WSDA sprays from the air to cover a large area, but that may not be necessary in this case, she said. “That’s definitely a possibility. It could be a ground treatment, rather than an aerial treatment.”
Moths captured by WSDA are sent to the USDA’s Otis Laboratory in Massachusetts for genetic testing to find out whether any are Asian gypsy moths. Asian gypsy moths, though rarer, are considered greater threats to agriculture, forests and landscapes because the females can fly, dispersing widely before laying their eggs.