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Like Moths to the Flames

Fire is more than a match for nuisances in the pine barrens

By Jennifer Smith | Staff Writer

August 3, 2003

Controlled burns can help reduce the population of oakworm moths and save oaks that the moths defoliate. (U.S. Fish and Wildlife Service)

On a sunny July day, thousands of female orange-striped oakworm moths hang from green oak leaves at Upton Reserve like velvety topaz ornaments.

These native moths, whose caterpillars will sustain themselves on oak leaves, are usually regarded as a minor nuisance. But the foliage at Upton has already been plundered once this season, large chunks eaten away by hungry European gypsy moth larvae hatched earlier in the spring.

It's a one-two punch that spells trouble for oaks in the central pine barrens. When this season's eggs hatch, the larvae will take up where gypsy moth caterpillars left off, further weakening trees already stressed by earlier defoliation.

"If you have a high population of gypsy moths followed by oakworm, your trees start dying," said Peter Kelly, a biologist with U.S. Fish and Wildlife, which manages the preserve on the grounds of Brookhaven National Laboratory.

Kelly estimates that gypsy moths have defoliated 30 to 45 percent of the oak trees on the 530-acre property this year. This has him worried. But he is loath to apply Bacillus thuringiensis, a microbial insecticide typically used to rein in infestations, in case it adversely affects other moths, flies and butterflies. So Kelly turned instead to fire, searching among the flames that once rolled at regular intervals through the pine barrens for insight on managing the problem.

On May 15, a 12-person crew from the state Department of Environmental Conservation performed a prescribed burn on a one-acre square of woods on the former Grumman site in Calverton, adjacent to Upton Reserve. Kelly's theory was that the flames, which licked as high as 15 feet up the trunks of the oaks and pines, would kill off enough orange-striped oakworms to severely restrict the number of adult moths emerging in July.

Preliminary data suggests that his hunch was correct. About 80 percent of the pupae found in a soil sample from the fire-treated area were completely burned out. Those that survived the fire had only a slightly lower emergence rate than those from the control area -- about 33 percent compared with 36 percent.

Ten paces into the unburned control acre round, jewel-like eggs cluster by the hundreds on the green undersides of oak leaves; orange-striped oakworm mating season is in full swing. Males still seeking mates flutter through the warm July air with the frenzied purpose of loners facing last call at a singles bar.

Far fewer females perch on what leaves remain in the treated area. Aerial surveys planned for later this year will show the damage caused by the offspring of these beautiful moths.

Kelly hopes that the controlled burn will serve a larger purpose: figuring out how to best steward an area whose plants are adapted to flame.

In their natural state, pine barrens woods are swept every 10 to 40 years by blazes large and small, which clear the undergrowth, giving plants greater access to light, moisture and nutrients from the sandy soil. In some cases the flames even trigger new growth -- as with dwarf huckleberry and dwarf pitch pine, whose cones scatter seeds only after heat has melted the resin that holds them shut. In the burn area, new stands of huckleberry and blueberry are already thriving, just eight weeks after fire cleared out the soft mat of decaying leaves and plant matter on the forest floor and let in air and light.

Much of the pine barrens in central Suffolk County are now hemmed in by development; fires in the woods place people and their property at risk. But there is a cost to suppressing the flames.

"By not allowing fire to do its normal thing in a fire-adapted ecosystem, the amount of leaf litter and fuel accumulates, and you get a Sunrise fire," said Kelly, referring to the 1995 fire that torched 5,000 acres of pine barrens along Sunrise Highway in Suffolk County.