Adaptation of the Southern Green Stink Bug, Nezara viridula (Hemiptera: Pentatomidae) to its parasitoid, Trichopoda pennipes (Diptera: Tachinidae)

Nezara viridula is an invasive, highly polyphagous stink bug pest that is difficult to control in both conventional and organic crops. Trichopoda pennipes is a dipteran koinobiont endoparasitoid of N. viridula that decreases its feeding, fecundity, and life span. Forty years ago, this host-parasitoid relationship was considered a landmark example of a successful ‘new association’ between an indigenous biocontrol agent and a new invasive pest, but these relationships are known to change over time as the host may develop some level of resistance to the parasitoid. To revisit this now well-established association, we collected N. viridula parasitized by T. pennipes from crops in Georgia and determined current rates of parasitism, along with egg placement on the host, degree of superparasitism, the resulting number of pupae, and yield of adults by sex. The results were compared with previous studies to ascertain the degree of host adaptation to the parasitoid. Additionally, controlled studies were conducted using laboratory colonies to determine the effect of host and parasitoid densities on the variables associated with parasitism. The results are being used to optimize a rearing system for N. viridula and T. pennipes by controlling superparasitism to maximize parasitoid yield. This study also could be used to estimate release rates of T. pennipes for augmentative biological control.