Photo by Sam Yu The leaves on this young tree Friday afternoon at the Frederick Towne Mall are starting to wilt due to current drought conditions.

This year's dry summer has trees dropping their leaves early as they conserve their energy for the future, said Mike Kay, Frederick County forester for the Maryland Forestry Service.

"Trees lose a lot of water through the stomata in the leaves, and to keep itself alive it will start dropping its leaves," Kay said.

Stomata are tiny pores beneath the leaves that regulate the tree's carbon dioxide intake. Trees, unlike grass, adapt pretty well to drought -- most develop extensive root systems which helps them tolerate dry years, Kay said. Trees in naturally wet areas have the most trouble, because they have shorter roots.

Trees are especially stressed this year not only because of the drought, but also a gypsy moth infestation.

"One thing that concerns me are the trees defoliated by gypsy moths," Kay said.

The Maryland Department of Agriculture has estimated that more than 5,000 acres of trees in Frederick County have suffered from gypsy moth infestations.

Gypsy moths are an invasive insect first introduced in Massachusetts in 1869. Gypsy moth caterpillars were first noticed on Maryland trees in 1972, and the first infestation in this state occurred in 1981. Gypsy moth infestations are mostly concentrated in Northeastern oak forests.

The caterpillars are most destructive to trees. The moths lay eggs on the branches and trunks and when the larva emerge in early spring, they munch on the leaves, sometimes stripping the tree entirely of its foliage.

This year was the worst gypsy moth infestation since 2003, said Bob Tichenor, chief of forest pest management for the Maryland Department of Agriculture. From 2000 to 2003, the state got a lot of federal help to battle gypsy moths, but this year, federal aid to fight the infestations is drying up.

"Typically trees with 60 percent or more defoliation will attempt to put out new leaves, but that's what weakens them," said Tom Lupp, regional entomologist for the forest pest management office of MDA. "As the leaves were starting to come out, it hasn't been excessively hot, but it's been warm and dry."

White oaks, the tallest oaks in Maryland forests, are the most affected as red oaks have had much better luck regenerating their leaves, Lupp said. Any tree putting out a second set of leaves is more susceptible to disease and drought in the years following the infestation.

Trees stressed by both drought and gypsy moths are especially susceptible to oak decline, which causes root rot, Kay said. Trees with root rot emit an aroma that attract insects, which will choke the tree.

That means two or three years after a major drought, trees could die. For some trees, death comes even slower.

"I'm seeing a lot of trees with oak decline from droughts in the late '90s," Kay said.

Oak trees dominate Frederick County's forests, but that could change as gypsy moths and drought become entrenched. They would be replaced by faster-growing red maples, black gum, sassafras and hickory trees.

This would change the forest habitat, Kay said. Oak trees provide acorns, a staple for deer, bear, squirrels and lots of other wildlife.

One way to preserve diseased oak trees is to cut them down, Kay said. Trees that are cut while diseased tend to resprout. Though it will take another decades for an oak to become mature, they can live for centuries, as evidenced by the Wye Oak, which died in 2002 after about 500 years.

Most homeowners don't have to worry about losing trees in their yards to the drought, Kay said. He recommended watering newly-planted trees once a week.

Trees need to develop root systems, and trees that are watered too much will only develop short root systems. Because trees need to survive periods of drought as well as periods of ample rain, those with good root systems are likely to live longer, healthier lives.

Trees will rebound if there is rain in the next couple of weeks, Kay said. Most do not yet have that curled-up leaf look they had after a much more severe drought in 1998, he said.

What could be more damaging this summer is the lower humidity the area has had, he said. Humidity helps moisturize trees when rainfall is scarce. Also, the northwestern area of the county, where oak forests are plentiful, has had more rain than the rest of the county, Kay said.