Tiny wasps set to wreak havoc on stink bugs

John Ferro
Entomologist Peter Jentsch (cq) holds a brown-marmorated stink bugs at the Cornell Extension's Hudson Valley labs in Highland N.Y.. Jentsch and other entomologists are studying and monitoring the invasive insect because it poses a serious threat to area orchard crops such as apples, pears and peaches.

HIGHLAND, N.Y. - Scientists are getting ready to escalate a life-and-death battle between two invasive insects: a stink bug that damages a wide variety of crops and a tiny wasp that just might become the hero in this drama.

If all goes according to plan, homeowners and farmers in as many as eight states will see fewer brown marmorated stink bugs infesting their houses and sucking the life from their fruits and vegetables.

The bug "is one of the most severe invasive agricultural pests because it feeds on so many different kinds of important crops," said Kim Hoelmer, an entomologist with the U.S. Department of Agriculture. "It is capable of doing a lot of damage."

Peter Jentsch,  director, Hudson Valley Research Laboratory in Highland, shows the damage that brown marmorated stink bugs cause on the interior of an apple after probing it for nutrition. The dark discoloration on the rear apple is a result of stink bugs 
using it as a food source.

In 2010, Mid-Atlantic apple growers blamed it for an 18% crop loss that cost them $37 million. A stink bug feeds by inserting its mouth into plants and removing juices like a milkshake.

Scientists have known for some time that a species of tiny wasp, Trissolcus japonicus — better known as the Samurai wasp — likes to lay its eggs inside stink bug eggs. The wasps do not sting humans, but what they do to stink bug eggs has been equated with the birth scene in the 1979 film Alien.

In the United States, the wasps haven't been able to breed quickly enough to slow stink bugs' spread. This year, scientists will try to change that.

For the first time, they will rear legions of Samurai wasps in the laboratory, infest stink bug eggs and then make like Johnny Appleseed with the compromised hosts. Out will come newborn wasps, presumably dooming more crunchy insects named for the odor they emit when smashed.

The rearing and release of wasps has been given the OK in Oregon. It is expected to be approved in New York, according to Peter Jentsch, director of the Hudson Valley Research Laboratory here.

A female Trissolcus japonicus wasp emerges from a parasitized egg of a brown marmorated stink bug, next to two other parasitized eggs containing unborn wasps and one egg with a hole left by a wasp that has already exited.

The process is being evaluated in six other states where the wasps have been found in the wild  — Delaware, Maryland, New Jersey, Virginia, Washington and West Virginia. Like stink bugs and many other invasive pests, the wasps were introduced unintentionally to North America from Asia.

The wasp discoveries are important because they can speed permitting processes within states. Federal approvals are needed if wasps are to be moved across state lines and introduced in a state in which they have not been found yet.

The wasps present a less worrisome approach to controlling stink bugs than spraying pesticides, scientists say. And studies have shown that when presented with a choice of egg hosts, the Samurai wasps typically choose those of the brown marmorated stink bugs.

In New York, the first discovery came this past summer. Jentsch and his co-workers placed stink bug eggs on the leaves of jalapeno pepper plants at Hepworth Farms, a family-owned organic farm in Milton.

"They love jalapeno peppers, probably more than any other plant," he said.

The scientists wanted to know if anything in the area was causing grief for the eggs.

"What you find is insects that chew on them, insects that steal them like ants, and then insects that probe them, such as other stink bugs," he said.

In this undated photo,
a group of Trissolcus
wasps are pictured 
against a dime.

They also found the tiny wasps injecting their own personal parasites into individual eggs.

"We got really lucky," Jentsch said. "There are a lot of other researchers who have put eggs all over creation for the last five years and captured nothing."

Now scientists have to hatch enough of those Samurai wasps to disperse them into the environment, Jim Walgenbach, a professor of entomology at North Carolina State University.

"We put out over 6,000 eggs last year," Jentsch said. "We need to quadruple that number. We are going to have stink bugs coming out of the woodwork."

Jentsch hopes to begin distributing the bad eggs this summer, he said.