Samurai wasp, Trissolcus japonicus, detected in Utah

    Samurai wasp, Trissolcus japonicus, detected in Utah

    Brown marmorated stink bug (BMSB; Halyomorpha halys Stål) is an economically important nuisance and agricultural pest that invaded North America from eastern Asia in the late 1990s. BMSB congregates in and on buildings during the winter, and is known to attack over 170 plant species, including fruit, vegetable, and nut crops, as well as herbaceous and woody ornamentals (see our host plants web page for a list of known host plants in Utah). BMSB was first detected in Utah in 2012. Populations are now established in Utah, Salt Lake, Davis, Weber, and Box Elder counties, and a few adults bugs have been detected in Cache and Kane counties. In 2017, BMSB feeding damage was first reported on some fruit and vegetable plants in multiple counties.

    Biological control, through the use of egg parasitoids, is the most suitable option for long-term management of BMSB. Researchers have found at least 12 native wasp species that can parasitize egg masses of BMSB, but these species typically account for less than 11% mortality of eggs (Rice et al. 2014). (The native parasitoids that have been found in Utah are described in the USU Extension fact sheet Parasitoid wasps of the invasive brown marmorated stink bug in Utah.) However, the samurai wasp (Trissolcus japonicus) co-evolved with BMSB in eastern Asia, and there, it is highly effective, with egg parasitism rates reported to be as high as 80%. The wasp has been identified as the most promising agent for classical biological control of BMSB in the U.S. 

    Trissolcus japonicus photo by Elijah Talamas [Public domain]On June 17 2019, two BMSB egg masses that were parasitized by T. japonicus were found on northern catalpa (Catalpa speciosa) leaves in Salt Lake City. This is the first detection of T. japonicus in Utah. These trees were in a managed urban landscape amidst residential homes. Both egg masses were found on separate trees planted approximately 9 meters apart from one another, and both egg masses were found approximately 2 meters above the ground. No guarding parasitoid wasps were seen at collection. Descriptions of individual egg masses are provided below. Three female wasps from egg mass # 2 were identified by Utah State University researchers and sent to Dr. Elijah Talamas (Curator of Hymenoptera, Mollusca, and Neuroptera for Florida Department of Agriculture and Consumer Services) for confirmation. All wasps from egg mass # 1 were identified by Utah State University. A lab colony has been initiated from wasps emerged from egg mass # 2.

    • Egg Mass #1: 28 BMSB eggs present; appearance at collection: all eggs were black in color; eventual fate of eggs: 28 T. japonicus emerged

    • Egg Mass #2: 27 BMSB eggs present; appearance at collection: 1 BMSB emerged; 5 eggs brown; 21 eggs black; eventual fate of eggs: 21 T. japonicus emerged


    Diane Alston, PhD
    Lori Spears, PhD
    Cody Holthouse (PhD Candidate)
    Zach Schumm (MS Candidate)
    Kate Morgan (lab technician)
    James Withers (lab technician)
    Erin Berdahl (extension intern / lab technician)
    Stephanie Hall (lab technician)

    Published on: Jul 08, 2019

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