Stink bug egg studies in southeastern Virginia: parasitoid survey, and susceptibility and chorion permeability to insecticides

Currently, there is little known about stink bug (Hemiptera: Pentatomidae) eggs, their natural enemies, and their susceptibility to insecticides.

A survey of stink bug egg parasitoids was conducted in row crops and vegetables in eastern Virginia. Parasitization was highest in Euschistus servus (Say) with 89.7% and 49.2% of egg masses and individual eggs parasitized, respectively, followed by Acrosternum hilare (Say), with nearly half of all individual eggs parasitized. The most common parasitoid was Telenomus podisi Ashmead (Hymenoptera: Scelionidae).

Laboratory egg-dip bioassays and field applications of acephate, lambda-cyhalothrin, spinosad, and thiamethoxam, were carried out to determine efficacy against nonparasitized E. servus and A. hilare eggs, and T. podisi embryos developing in E. servus eggs. Results showed that eggs of both species were susceptible to insecticides, that there was little difference among insecticides, but there was generally greater mortality in field-treated versus dipped eggs. Developing T. podisi were generally more susceptible to insecticides than stink bugs.

Scanning electron microscopy was used to investigate oviposition sites as possible sites of insecticide movement into eggs. Oviposition wounds and holes made by a tungsten probe were similarly sealed by a "scab", so it was not clear whether these wounds allow for increased insecticide movement into parasitized eggs.

Differences in chorion permeability of non-parasitized and parasitized eggs were compared by immersing them in solutions containing different ¹⁴C-ammended insecticides at field application rates for 0, 30, 120 or 240 minutes. Results showed that insecticide movement into the egg increased significantly with immersion time for both acephate and λ-cyhalothrin, but there were no significant differences between nonparasitized and parasitized eggs. Neither immersion time nor egg status was significant for thiamethoxam. A model was constructed that predicts amount of insecticide entering the egg at any given time.

An 8-week survey for the brown marmorated stink bug, Halyomorpha halys (Stål) was conducted in Beijing and five other cities in China. Incidence of egg parasitism was recorded. Results showed that H. halys utilized at least four different plants throughout the summer, and insects were found in Nanjing, Kunming, and Xi'an. Parasitization of eggs was noted, and the parasitoids were identified as Trissolcus halyomorphae Yang (Scelionidae: Hymenoptera) by K.A. Hoelmer (USDA-ARS).