Gypsy moths have no appetite for county trees this year, which means the state will not spray to eradicate the pests in Carroll for the first time in 10 years.
The lull doesn't mean the moths won't be back, however, said Robert H. Tichenor Jr., chief of the Forest Pest Management Section of the Department of Agriculture.
Gypsy moth populations wax and wane in different areas for a number of reasons, some of which are hard to predict, he said.
Weather makes a difference, and so does the population of white-footed deer mice, which eat the moths, he said.
Surveys last fall found that the gypsy moth population "next to nothing" in Carroll, making it unnecessary to spray, Tichenor said.
The insects devour tree leaves while in the caterpillar stage. They lay eggs in July and begin hatching in the spring.
When the state spraying program began in 1982, 1 acre of forested land in the county was defoliated, Tichenor said. The state has sprayed every year since.
The moths did the most damage in Carroll in 1986, when 4,393 acres were defoliated, state numbers show. That year, 11,040 acres were sprayed in the county.
Last year, the state sprayed 1,397 acres, and no land was defoliated.
The pests are doing more damage this year in southern and bTC western Maryland and on the Eastern Shore, Tichenor said.
Crews are spraying on the Eastern Shore and southern Maryland now, and will begin in the western part of the state soon, he said.
Calvert is the only county in Maryland that has never had a problem with gypsy moths, Tichenor said.
The pests were introduced in the United States from Europe in the 1860s and first appeared in Maryland in 1971. The moths have been destructive in Michigan, but generally haven't gone west of Ohio, Tichenor said.
The state budget for spraying was reduced by about 30 percent this year, but the cut won't affect the program's effectiveness because the gypsy moth population is down overall, he said.
Last year, 150,286 acres were sprayed in Maryland; this year, about 83,000 acres will be treated, Tichenor said. The state has about 2.7 million acres of forest.
Two insecticides are used in the state to kill the caterpillars: B.t., or Bacillus thuringiensis, and Dimilin, or diflubenzuron.
Neither chemical has been found to have toxic side effects on humans.