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Stinkbugs’ natural predator has arrived in the Pacific Northwest

Eric Mortenson

Capital Press

Published on July 28, 2016 4:04PM

A tiny parasitic wasp of the type recently discovered in Portland emerges from the egg of a brown marmorated stinkbug, which can cause heavy crop damage. Wasp females lay their eggs inside those of the stinkbug. The developing young feed on the host before emerging, killing it.

Courtesy of Oregon Department of Agriculture

A tiny parasitic wasp of the type recently discovered in Portland emerges from the egg of a brown marmorated stinkbug, which can cause heavy crop damage. Wasp females lay their eggs inside those of the stinkbug. The developing young feed on the host before emerging, killing it.

The brown marmorated stinkbug, an invasive pest, feeds on a wide variety of crops and potentially could cause heavy damage to Oregon agriculture.

Courtesy of Oregon Department of Agriculture

The brown marmorated stinkbug, an invasive pest, feeds on a wide variety of crops and potentially could cause heavy damage to Oregon agriculture.


Discovering the Portland presence of a wasp that kills the eggs of the dreaded brown marmorated stinkbug might be cause for more head scratching than fist bumps, but researchers will take good breaks where they find them.

The Oregon Department of Agriculture announced that one of its entomologists discovered a cluster of stinkbug eggs in Portland that had been obliterated by a tiny, parasitic wasp called Trissolcus japonicus. The finding may speed up control of brown marmorated stinkbug.

Like the stinkbug, referred to as BMSB, the wasp isn’t native to Oregon. The female wasp lays its eggs inside the eggs of stinkbugs. The developing wasp larvae essentially eat their way out as they grow, destroying the host.

That trait caught they eye of researchers at ODA, Oregon State University and elsewhere, because BMSB will eat nearly anything and are considered a major threat to fruit, berry, vegetable and nut crops. Its discovery in southeast Portland’s venerable Ladd’s Addition neighborhood in 2004 touched off a program, funded by the USDA’s Agricultural Research Services, to find a method of biocontrol, as bug-on-bug predation is called.

The state ag department leases space at OSU, which cooperates in the research, to raise the wasps in quarantine and sic them on BMSB in the laboratory.

One of the key questions is whether the wasps might harm beneficial native bugs as well. Entomologists have been working on it since 2011; the idea is to gather enough data to petition USDA’s Animal Plant Health Inspection Service for permission to release the predator wasps. Researchers in New York, Delaware, Florida, Michigan and California are doing similar work.

In 2014, things began to go sideways. The wasp was found in a mid-Atlantic state, and researchers immediately suspected wasps had escaped from quarantine. But DNA analysis showed it wasn’t from any of the colonies that researchers around the country keep in quarantine.

Last summer, the same thing happened in Vancouver, Wash. A wasp was recovered by Washington State University, but it also wasn’t from any of the quarantined populations. What’s more, it wasn’t from the same group as the wasp caught in the mid-Atlantic state.

This summer, entomologist Chris Hedstrom of ODA was checking a private property site near Oregon Health & Science University in Portland when he came across a cluster of BMSB eggs by accident.

The eggs had been wiped out, and it was clear wasp larvae were to blame. Wasps roughly chew their way out, while stinkbugs emerge through a neat hole, Hedstrom said.

“Oh, we have something here,” Hedstrom described his reaction.

Recognizing the potential importance of the find, Hedstrom returned within 15 hours and set what are called “sentinel” traps baited with BMSB eggs collected in ODA’s laboratory in Salem.

Two days later, he found wasps had struck again. He collected the eggs and adult “guardian” wasps that hang to protect the cluster from other parasitoids after they’ve deposited their young into the BMSB eggs. A single female can parasitize an entire egg cluster, Hedstrom said.

In July, the wasp larvae emerged in captivity and have since been identified as Trissolcus japonicus.

Additional study by the Smithsonian’s Systematic Entomology Lab will determine the lineage of the Portland wasps. Hedstrom believes they are part of the Vancouver group, given the relative proximity.

He said the wasps probably arrived in the Pacific Northwest the same way BMSB did — by hitching a ride into the Port of Portland or Port of Vancouver.

Hedstrom said the findings may speed up the process of gaining APHIS approval to release wasps as a biocontrol agent.

Hedstroms said the development is encouraging after years of telling growers it will take more time before biocontrols gain approval.

“We still have to error on the side of caution,” he said.



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