Hopeful news about stink bug biocontrol

The news about the brown marmorated stink bug (BMSB) has generally been bad over the past few years, as this new invasive pest has continued to expand its range within the USA, causing increasing problems as a pest of fruit, vegetable, and field crops. We know that our native natural enemies have not been able to provide much biological control of BMSB, but there has been hope about potential biological control of BMSB by a tiny wasp that parasitized BMSB eggs in China. The wasp is Trissolcus japonicus, nicknamed the samurai wasp.

USDA entomologists at Newark, Delaware, have been conducting intensive studies of the samurai wasp over the past 10 years with the hope that it could be introduced into the USA for control of BMSB, but thus far its introduction has not been approved. However a significant event occurred in 2014, when the samurai wasp was detected outdoors in Maryland, where it apparently showed up on its own, probably via a parasitized BMSB egg mass present in cargo shipped from Asia. In 2015, the samurai wasp was also detected in Virginia, Delaware, and Washington State. In 2016, it was detected in New Jersey, New York, and Oregon. In 2017, it was detected in Pennsylvania. Once an exotic species like this has been detected, it can be studied and intentionally spread within any State, but it is not allowed to be transported across State lines.

In Ohio, as part of our involvement in a multi-State project on BMSB management, we surveyed for the possible presence of the samurai wasp within Ohio in 2017. To do this, we collected fresh egg masses from our lab colony of BMSB; we deployed the egg masses in the field by clipping them to the underside of leaves, mostly on plants in wooded edges adjacent to fruit and vegetable crops. The egg masses were left outside for 3 days, then brought back to the lab where we observed whether they eventually hatched into stink bugs or if they were parasitized. We deployed 544 egg masses between May and September at several Ohio locations. Over the winter, we have been working our way through these samples, and identifying wasps that emerged from parasitized eggs. This past week, we found that wasps that emerged from two egg masses were identified as the samurai wasp. The two egg masses were deployed in Columbus in early August 2017. This finding that the samurai wasp has spread to Ohio is quite exciting. We plan to do additional surveys in 2018 to determine whether it is present at additional locations within Ohio.


by Celeste Welty, Extension Entomologist

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