Toward optimized surveillance of adventive Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) based on aspects of its foraging ecology

Abstract

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), an invasive agricultural pest from Asia, has established in much of the USA, where it has had significant, deleterious impacts on the production of various specialty crops. Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) is the predominant egg parasitoid of H. halys in Asia and considered a potential agent for classical biological control. Adventive T. japonicus populations have been detected in 15 US states since 2014 and its continued spread is anticipated, creating the impetus for developing optimized sampling methods for it that are informed by its foraging ecology. Yellow sticky cards (YSC) deployed in the lower and mid-canopy of Ailanthus altissima (Mill.) Swingle trees in Virginia captured statistically equivalent numbers of T. japonicus. Season-long monitoring of T. japonicus and H. halys over two seasons resulted in significant correlations between captures of T. japonicus and H. halys adults, second instar nymphs, and all life stages combined, revealing spatiotemporal synchrony between the parasitoid and its host. Inspection of felled pheromone-baited and non-baited A. altissima showed no effect of baiting with the H. halys aggregation pheromone on H. halys egg mass abundance. Similarly, captures of T. japonicus in pheromone-baited and non-baited trees were not significantly different. Augmenting YSC with H. halys egg masses or n-tridecane did not improve T. japonicus captures. Together, these results should improve the efficiency of T. japonicus surveillance efforts and provide important guidance for future research toward enhancing the sensitivity of sampling tools for it and the interpretation of its impacts on H. halys.