It's spring, and that means the gypsy moths are coming.
But state entomologists say the leaf-munching bugs are in a sort of reproductive lull in densely settled parts of Maryland, so aerial spraying this spring will be reduced.
"We're seeing susceptible areas come in and out of peaks on a four- or five-year cycle," said Robert H. Tichenor, chief of Maryland's gypsy moth program. "Right now ... the south-central part of Pennsylvania and the north-central part of Maryland is all one big quiet area."
The Maryland Department of Agriculture's aerial spray program, set to begin in early May, will attack gypsy moth larvae across about 160,000 acres, Tichenor said. That's down almost 15 percent from the 187,700 acres sprayed last year.
Where spraying is needed, there are fewer people. The number of property owners in spray zones this year totals about 43,000, half of last year's total, Tichenor said.
In Baltimore County, the state's spray targets have been halved, from a record 16,459 acres last year to just 8,261 acres this year, mostly in Middle River and White Marsh.
Similar cutbacks in spraying are planned in Howard and Montgomery counties.
There will be no aerial spraying at all this spring in Baltimore.
Anne Arundel County will spray 11,867 acres in Linthicum, Severn, Pasadena, Severna Park, Millersville, St. Margarets, Annapolis, Edgewater and Davidsonville. That's down from 13,490 acres last year.
Gypsy moth populations remain relatively low in most of Southern Maryland. Numbers on the Eastern Shore and in Western Maryland have remained stable, Tichenor said.
The $2.5 million spraying bill will be shared by the federal government, which pays half, and the state and counties, which pay 25 percent each.
The spraying slowdown does not mean gypsy moths are no longer a threat to Maryland's hardwood trees. It only means their attack on high-value trees in metropolitan areas has subsided temporarily, reducing the need for spraying.
Tichenor said gypsy moth caterpillars defoliated a record 133,062 acres of trees last year, the first time the statewide toll has topped 100,000 acres. In 1989, fewer than 98,000 acres were defoliated.
"I don't think we're going to have a number as high as that this year, but that is only a guess," he said.
A Eurasian pest accidentally released in Boston in 1869, the gypsy moth has been spreading southward ever since. It reached Maryland in 1969 and began causing serious damage here in 1981. It now causes damage totaling millions of dollars each year to hardwood trees, especially oaks, by eating newly emerged leaves. Defoliated trees are weakened and prey to fatal infestations, drought and disease.
As Marylanders have become more familiar with the gypsy moth and the spray program, the number of property owners asking to be dropped from planned spray zones has fallen.
Of the 14,000 property owners in Baltimore, Harford, Cecil and Kent counties notified by mail that their trees were targeted for spraying, fewer than 10 asked to be dropped from the program, said Robert Tatman, the regional entomologist.
In Anne Arundel County, only four of 13,000 property owners said they wanted out, and there were no objectors among the 3,000 owners in Carroll and Howard counties, according to regional officials.
Three years ago, when the gypsy moth infestation first struck hard in the Baltimore area, the state's residential spray program provoked a controversy. Concerned homeowners forced thousands of acres to be dropped from the spraying, especially in the Towson and Reisterstown areas.
There is no aerial spraying planned this year in Towson or Reisterstown.
"In the areas we're spraying this year, especially in Baltimore County around Middle River and White Marsh, it's been very bad for several years in a row, and there are very few people opposed," said Tatman.
This year's spray program will employ the same two pesticides used in recent years: Dimilin, a synthetic hormone that kills by interfering with the caterpillar's molting; and Bacillus thuringiensis, or Bt, a naturally occurring bacterium regarded as environmentally safe.
Dimilin is toxic also to certain aquatic insects and crustaceans. The state's own rules bar the use of Dimilin near streams and bay waters.
Statewide, Tichenor said, this year's spray plans call for the use of Bt across 62 percent of the targeted acreage. Plans for spraying in Baltimore County call for Bt across 80 percent of the sprayed acreage.
Tichenor said the greater use of Bt in the county "reflects the fact that we're concentrating our activity where the problem is, in White Marsh and Middle River, so there are a lot of [spray] blocks near the water and [Chesapeake] Bay critical areas."
Tichenor also said that where gypsy moth populations are down this year property owners should continue to protect vulnerable trees, especially oaks, with sticky bands now and burlap flaps from May through mid-July. Instructions are available from the University of Maryland Cooperative Extension Service.
"This is the time when individuals have the greatest impact," he said.
"Barrier bands are one of the more worthwhile activities, and it should be done in the next two weekends," he said. "You want the barrier on trees to prevent the initial invasion of all those tiny little larvae."
"I don't suggest you do the burlap unless you're willing to pick off the caterpillars every day," he said. Left untended, the burlap flap provides shelter to the insects and "helps them survive."