The Asian micro-hymenopteran wasp, Trissolcus japonicus, (Hymenoptera: Scelionidae) is considered one of the primary parasitoids of the brown marmorated stink bug (BMSB) Halyomorpha halys, in its native region of origin. A common name presently under consideration is the Samurai wasp. Asian fruit growers consider BMSB as only a secondary pest of apple, likely due to the suppression of BMSB provided by native biological controls that include Trissolcus japonicus.
After the severe tree fruit losses from BMSB in the mid-Atlantic in 2011, a team of USDA researchers, including lead entomologist Kim Hoelmer, traveled to Asia to find native predators and parasites of the newly invasive stink bug. A survey of parasitoids was conducted in China & Korea, collecting species of wasps to bring back to the US for further study under quarantine in the USDA laboratory’s in Newark, Delaware.
Trissolcus japonicus became a prime biological control candidate for BMSB, able to parasitize up to 90% of the eggs in a BMSB cluster while under quarantine, demonstrating high efficiency and limited impact on the native predatory stink bug complex during choice and non-choice studies. This tiny wasp is now considered a viable biological control agent for release to control BMSB in the U.S. where it has become an important agricultural and urban household pest.
It was quite a surprise when in 2014, a survey of resident egg parasitoids of the BMSB by Don Weber, (ARS-Beltsville Area Research Center), using sentinel brown marmoraed stink bug egg masses, revealed that T. japonicus was present in the wild at one of his study sites in Beltsville, MD. Since then, several T. japonicus wasp clusters have been found in Maryland and Virginia over the past two years. More recently, it appears that T. japonicus was also found in Vancouver, Washington.
To add to these finds, we have also captured T. japonicus in the Hudson Valley of New York over the past 2 weeks, using sentinel brown marmoraed stink bug egg masses. This work was fully supported by program funds directly from the NY State apple growers.
Beginning 22nd of July 2016, Cornell faculty and staff stationed at the Hudson Valley Research Lab began a baseline study to determine levels of parasitism of brown marmorated stink bug egg laying. We employed BMSB eggs that had been frozen for 3 minutes in -80C, used to reduce the natural defense mechanism of the eggs to parasites. We chose two locations in two counties in the mid-Hudson Valley that had both high traffic of plant products on and off of farms to increase the chance of finding invasive parasitoids that had moved into the region on plant material from the south.
To date 108 clusters containing 3024 eggs were placed in each site with only a single location within one of the sites found parasitized emerging in late August.
In Ulster County, eggs were placed along the wooded edge perimeter of organically grown Jalapeno pepper in Marlboro, NY, stapling egg masses to the leaves of the Asian invasive tree, Tree of Heaven, Ailantus altissima and Black Walnut. The BMSB eggs placed in early and mid-August began to darken, indicating development of parasite larva within the egg. From these we found 70-90% of the individual eggs in each cluster of approximately 28 eggs parasitized. By early September microhymenopteran in the Genus Trissolcus was found successfully emerging from BMSB eggs. Adult wasps were sent to Elijah Talamas, Research Entomologist at the USDA Systematic Entomology Laboratory in Washington, DC for confirmation.
Our second site in which sentinel brown marmoraed stink bug egg masses were placed along the perimeter of peach and apple plantings of a conventional orchard in Warwick, NY has yet to produce parasitic wasps from BMSB egg clusters.
This first observation of Trissolcus japonicus in NY is an important development to farmers as well as homeowners. For the grower of fruit and vegetable, it signifies a step toward the sustainable management of a very unpredictable agricultural pest. If T. japonicus can overwinter and build in numbers in NY we will likely see increasing levels of biological control of BMSB. This may lead to moderate and low level populations in deciduous forests with reduced damage to fruit and vegetable crops during the growing season.
The second benefit of increasing biological control would of course be to homeowners, with lower numbers of BMSB adults in homes and offices over the next few years.
Our short term research goals will include expanding our monitoring range of T. japonicus in other Southeastern NY Ag. sites. We plan to expand our Citizen Science Project mapping using EddMaps/BMSB to reach out to the public who have contributed to our understanding of the spread of BMSB in NYS. We hope to determine if BMSB populations are changing in urban areas while searching for T. japonicus using sentinel BMSB egg surveys.