Gypsy moth caterpillars are now dining on leaves of their favorite trees -- oaks, sweet gum, linden, willow, apple, alder and box elder. Left alone, the caterpillars will continue to grow and eat through June.
Healthy trees can be defoliated and recover. But trees stressed by age, drought or disease may die, especially if stripped repeatedly.
Commercial tree care companies can spray individual trees. County offices of the Cooperative Extension Service can provide lists of area firms equipped to treat trees more than 60 feet tall.
Homeowners can further protect vulnerable trees by placing 2-inch-wide sticky bands around the trunks to prevent caterpillars from climbing up from the ground. The barriers are available at hardware or garden stores or can be made inexpensively using duct tape and a commercially prepared substance like Tanglefoot.
Burlap flaps can be tied to vulnerable trees above the sticky bands to attract caterpillars seeking shelter from heat. The 12-inch-wide flaps should be checked daily, and any caterpillars should be crushed or swept off and drowned in soapy water. Failure to check the flaps and destroy the caterpillars will worsen the infestation. Both devices should be removed by Aug. 1 to avoid damaging the tree.
For detailed information on how to cope with gypsy moths, contact the Cooperative Extension Service's Home and Garden Information Center at (800) 342-2507.
Maryland residents can buy a 12-minute videotape, "A Homeowner's Guide to Gypsy Moth Control," for $11.95. To order, write the Cooperative Extension Service, University of Maryland, 0120 Symons Hall, College Park, Md. 20742, or phone (301) 405-4594.