By Bruce Scruton
MIDDLE SMITHFIELD, Pa. — Three species of a small wasp that can attack the eggs of the emerald ash borer were released by National Park Service biologists within the Delaware Water Gap National Recreation Area this past weekend.
The borer, an invasive beetle from Asia, is capable of killing a full-grown ash tree within a couple of years and has been found in several locations in Sussex County in the past two years.
The release was in the Mosier’s Knob area, just below the Walpack Bend of the Delaware River and across the river from Worthington State Forest where the New Jersey Department of Agriculture recently released its own biological agents to stem the invasion of the pest.
Kara Deutsch, chief of resource management for the park, said the emerald ash borer has been found on both sides of the river. The choice of Mosier’s Knob for the release came at the recommendation of regional NPS experts.
The wasps, known in scientific circles as “parasitoids,” were supplied by the United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) and came from the Plant Protection and Quarantine (PPQ) EAB Parasitoid Rearing Facility in Brighton, Mich.
There were three species of wasps released — one release was of adults and the others were pupae of separate species.
The three are themselves invasives, native to the Asian areas where the emerald ash borer are native. The borer was imported to this area first identified in the area around Detroit and believed to have arrived in 2002 inside of wooden packing material.
In less than two decades since, the borer, a type of beetle, has been found in the U.S. from the Atlantic Coast (except Forida) as far west as Colorado and has spread throughout the eastern two-thirds of Canada.
The wasp parasites — the adults are about the size of a mosquito and don’t sting — get the borer in both egg and larval states.
The adult Oobius agrili female will lay her own egg inside the egg of an ash borer and there are two life cycles of the wasp for one life cycle of the borer. In experiments and observation, more than half an emerald ash borer’s eggs became victims of the wasp.
The other two wasps attack the larval stage of the borer and it is that stage that causes the damage to ash trees.