Floral Resources for Trissolcus japonicus, a Parasitoid of Halyomorpha halys

Abstract

The egg parasitoid Trissolcus japonicus is the main candidate for classical biocontrol of the invasive agricultural pest Halyomorpha halys. The efficacy of classical biocontrol depends on the parasitoid's survival and conservation in the agroecosystem. Most parasitoid species rely on floral nectar as a food source, thus identifying nectar sources for T. japonicus is critical. We evaluated the impact of eight flowering plant species on T. japonicus survival in the lab by exposing unfed wasps to flowers inside vials. We also measured the wasps' nutrient levels to confirm feeding and energy storage using anthrone and vanillin assays adapted for T. japonicus. Buckwheat, cilantro, and dill provided the best nectar sources for T. japonicus by improving median survival by 15, 3.5, and 17.5 days compared to water. These three nectar sources increased wasps' sugar levels, and cilantro and dill also increased glycogen levels. Sweet alyssum, marigold, crimson clover, yellow mustard, and phacelia did not improve wasp survival or nutrient reserves. Further research is needed to determine if these flowers maintain their benefits in the field and whether they will increase the parasitism rate of H. halys.

Keywords: biocontrol; biological control; brown marmorated stink bug; conservation; flowers; longevity; nectar subsidy; samurai wasp; survival.

Figure A1

Survival curves of male Trissolcus japonicus fed flower treatments, honey, or water inside vials in the lab. Per results of log-rank analysis and post-hoc tests, lines with different letters are significantly different from each other.

Figure 1

Survival curves of female Trissolcus japonicus fed with flower treatments, honey, or water inside vials in the lab. Per results of log-rank analysis and post-hoc tests, lines with different letters are significantly different from each other.

Figure 2

Kernel density plots of nutrient levels of female Trissolcus japonicus fed with flower treatments, honey, or water for 48 h inside vials in the lab. Internal boxplots show the median, interquartile range, maximum, and minimum. Treatments with different letters are significantly different based on Tukey post-hoc tests.