Biological stink bug control being developed in Maryland

The invasive brown marmorated stink bug (Halyomorpha halys) was first discovered in the U.S. in Pennsylvania in 2001. The insect rapidly proliferated here, in the absence of natural controls that help keep it in check in its native habitat in Asia.

The population of the Asian brown marmorated stink bug, an invasive pest, may be able to be controlled. It has been causing significant crop damage to fruits and vegetables in the 41 states where the brown marmorated stink bug is now found.

Credit: - Elijah Talamas, USDA ARS

For several years, the US Department of Agriculture Agricultural Research Service has conducted research using the tiny 1 to 2 millimeter long beneficial Samurai wasp (Trissolcus japonicus) found in Asia that uses the stink bug eggs in which to lay its own eggs. The developing wasp larvae consume the stink bug eggs as they develop into mature wasps.

Related tiny wasps of the same family native to the U.S. help contain native species of stinkbugs. The USDA uses a quarantine ARS laboratory in Maryland for its research using Asian wasps to assure that this non-native species is not released into the wild in the U.S. until its potential impact is fully understood.

However, last year, USDA researchers found that some brown marmorated stink bug egg masses collected in the Beltsville area had been pariticized by the Asian wasp and other egg masses were being decimated by the related native wasp species.

The tiny size of the wasp Trissolcus japonicus is apparent from this dime, which has several of the insects sitting on it.

Credit: - Ashley Colavecchio

A report of this research showed about one-sixth of the brown marmorated stink egg masses had been used as hosts by tiny parasitic wasps, with about a third of the parasitic wasps of the Asian variety.

While finding the Asian beneficial wasp actively attacking stink bug egg masses in the outside environment was unexpected, the fact that some of the invasive stink bug egg masses are being destroyed by beneficial wasps is viewed as a step forward to natural control.

Similar results were recently confirmed in June of this year by University of Maryland researchers using brown marmorated stink bug egg masses at an entirely different location 30 miles from the Beltsville site. The 2015 data also shows the Asian wasp (Trissolcus japonicus) is in the area, and is attacking the stink bug egg masses.

Both research projects are limited in scope and very recent, yet they show that parasitic control of the invasive stink bug is beginning to occur.

Several theories about the evolution of natural stink bug controls are developing. Firstly, native tiny beneficial wasps, of which there are several species, are adapting to the new stink bug invader and finding that its egg masses can be used as hosts.

Further, the Asian beneficial wasp is confirmed to have found its way into the U.S., apparently from importation of products from Asia, just as the invasive brown marmorated stink bug came to the U.S.

So far, the tiny Asian wasp hasn’t shown any adverse effect on the environment, as it behaves similarly to the related native species, using the stink bug egg masses as part of its life-cycle. In addition, birds, amphibians, and other animals have found easy meals, consuming adult brown marmorated stink bugs.

The overall effect of these growing environmental controls is that there seem to be fewer stink bugs around than in past years.

Article by Tom Anderson, FCFCDB member

Nature Notes for 8/30/2015