A note about why I’m looking for stink bugs

 The wasp pictured here is Trissolcus japonicus (Hymenoptera: Platygastridae), a potential biological control agent against brown marmorated stink bug (BMSB), an invasive pest. Although this picture makes it looks pretty large, it’s only a couple of millimeters in length. T. japonicus, like other Trissolcus wasps, lays its eggs into stinkbugs eggs, where the larvae develop, killing the developing stink bug nymphs. It was collected in Asia, the native range of BMSB. In experiments there, it was very effective in parasitizing BMSB eggs, with a success rate of over 90% in killing the host eggs.

Parasitoid wasps can be an effective method of managing pest insects that have become established outside of their native range. Invasive insects often become a problem because the organisms (such as parasitoids) and diseases that kept their populations in check in their native range aren’t always present in the newly established regions, and their populations can grow without hinderance. Parasitoid wasps are often very host specific, having evolved over thousands and millions of years with their host to be able to overcome the host defenses. This makes them a good candidate for biological control because their is less risk of the biological control agent going “off target” or attacking organisms that you don’t want it to.

The scientists who research biological control agents do so with the intention of minimizing risk. Nobody wants the insects to attack everything: not only could their be unintended ecological consequences, but it would also minimize the effectiveness of the agent in terms of management. If the released agent goes after many species instead of the one that it’s intended to, resources are spread over a much broader range than if it just attacked the target organism.

Potential biological control agents go through many levels of evaluation before there is a chance of them being released. Currently, T. japonicus is being housed in a couple of Quarantine Facilities where researchers, such as myself, are exposing the wasps to stink bugs that are endemic to regions where BMSB is a problem, such as Oregon. The purpose is to determine if T. japonicus can reproduce on the stink bug eggs of endemic species. If it’s determined that T. japonicus can easily survive using other species as a host, the likelihood that it will be released into the wild is very low to nil. If it is not very successful in reproducing on the “non-target” (non-BMSB) hosts, researchers will collectively apply for a release of the agent. Results of experiments are evaluated by USDA-APHIS, and a decision is made. There are no set rules for how far “off-target” an arthropod-to-arthropod biological control agent can go to prevent it from being released (or to guarantee its release). Decisions are based on risk-benefit analysis. For arthropod-to-weed biocontrol agents, there are set numbers.

The research is currently underway for T. japonicus’s release is the United States, which is why I am driving around Oregon looking for stinkbugs. The response by many people who hear about this research is to mention the risks involved in releasing a novel organism into a new area. We are aware of the risks. Hence, the reason for the research at all. Another quippy response that often surfaces is “It’s not a good idea to release one invasive to attack another”. There’s no evidence that T. japonicus is an “invasive” insect. In fact, the reason it’s the top candidate is because in preliminary studies in it’s home range, it appeared to be very dependent on BMSB as a host for its survival.

I enjoy talking about my research and discussion the pros and cons, risks and benefits of biological control, so I encourage you to ask questions about this project. It’s been my experience that a lot of people don’t realize how often how successful this management method can be. True, there are disasters that are often cited as arguments against biological control, but often these releases were not made by scientific researchers, were accidental, or we not researched at all before released. Or they happened decades ago, when subjects like ecology and ecosystems were just beginning to take shape. It’s my opinion that biological control is a better management strategy than heavy, broad spectrum pesticide use against invasive pests, which is often the other alternative. The best alternative would be to reduce importation of foreign goods and food, or to increase border inspection sites for pests (or both), but those are not going to happen anytime soon.

Here’s a link to a video that I put together showing the life cycle of T. japonicus: