Skip to main content
Hero Image
ARS entomologist and a technician examine symptoms of emerald ash borer infestation on a sample tree.

ARS entomologist and technician examine symptoms of emerald ash borer infestation on a sample tree.

Wasp Recruited to Fight Emerald Ash Borer

An adult wasp on the bark of an ash tree
An adult wasp drills through ash bark to lay eggs on the emerald ash borer larva feeding beneath the bark. (Jian Duan, D4734-1)

A tiny, stingless wasp is earning high marks as a biological control agent against the emerald ash borer (EAB), an invasive, wood-boring beetle from Asia. The metallic-green, half-inch-long pest has killed hundreds of millions of ash trees in North America since 2002. Adult beetles nibble at ash leaves, but it is the larvae that cause the real harm, by feeding on the inner bark and disrupting the flow of water and nutrients to the rest of the tree, killing it in 3 to 5 years. Chemical insecticides can be an effective control measure for individual trees, but repeat treatments are needed every year or two, and widespread applications are not feasible.

As an alternative, scientists with ARS, the Forest Service, and Animal and Plant Health Inspection Service searched for natural enemies of the beetle in its native range, particularly northeast China and the Russian Far East. One promising candidate was Spathius galinae, a 5-7 millimeter-long parasitic wasp that lays its eggs on EAB larvae but poses no danger to people, pets, or other animals. When the eggs hatch, the wasp’s own larvae feed on their much larger host, killing it. After carefully evaluating the wasp’s host specificity, scientists released it in EAB-infested areas of Connecticut, Massachusetts, and New York. S. galinae established a self-sustaining population 3 years after its initial release and spread more than 8 miles from the original release points, parasitizing 35 to 78 percent of EAB populations and reducing its densities there.


Related Information

Article: Controlling Emerald Ash Borer

Explore Other Discoveries

Food Additive Takes on Duty as a Pesticide

ARS scientists found that methyl benzoate can repel, and even kill, other insects and pests, including the spotted wing drosophila fly.

For the Love of Coffee

ARS scientists studied Puerto Rican fungal strains as possible biological control agents for managing the coffee berry borer in an environmentally sustainable manner.

Herbicide Beefs Up Effective Biofumigant

Combining the biofumigant with an herbicide seems to curb infestations of purple nutsedge as well as reduce nematodes and the tomato wilt bacterium.

Hopping Against Climate Change

Often viewed as pests, grasshoppers may have a larger environmental role to play.

New Sugarcane Sweetens the Deal

A new variety of sugarcane has high fiber content, excellent regrowth ability, high stalk population, cold tolerance, disease resistance, and excellent biomass yield.

Saving A Favorite Superfood

ARS scientists are combatting pests and diseases affecting avocado production in the U.S.

The Buzz Around Bee Genomics

Researchers with the ARS Honey Bee Breeding, Genetics, and Physiology Research Unit have identified a region of the honey bee genome linked to reduced colony defensiveness.

The Potato Industry’s New Stud

ARS scientists created a new potato variety with greater yields and better processing qualities, especially for making chips and fries.