The Potential for Conservation Biological Control of Pentatomids and Plataspids in North Carolina

Ecological functionality of agricultural landscapes can be utilized to conserve natural enemies and to support biological control of insect pests. In the present study, the need for information regarding a native egg parasitoid and an invasive exotic pest has been addressed. Telenomus podisi (Hymenoptera: Scelionidae) has been reported to be the predominant egg parasitoid of stink bugs (Hemiptera: Pentatomidae) attacking important vegetable crops in the southeastern US. Laboratory and field studies were conducted to contribute to the information regarding T. podisi carbohydrate utilization and overwintering behavior. Access to carbohydrate resources plays an important role and naturally available resources such as homopteran honeydew and nectar are utilized by parasitoids. Typically, honeydew has been reported to be an inferior nutritional resource compared to nectar. In this study, T. podisi was offered honeydew from three different aphid species: cowpea aphid, pea aphid, green peach aphid; flower nectar of buckwheat; and clover honey (processed and organic) for assessing their longevity and fecundity. It was found that honeydew from cowpea aphid was as good a food source as nectar based on T. podisi longevity, fecundity and progeny sex ratio. In terms of fecundity, all carbohydrate resources proved to be equivalent. Interestingly, T. podisi continued to kill host eggs even during their post-ovipositional period, although at lower rates. Honeydew from pea or green peach aphids proved to be less suitable, which may have been caused due to presence of unsuitable sugars and/or toxins. It appeared that T. podisi lacked the ability to breakdown melezitose (a common trisaccharide present in honeydew), indicating that T. podisi may have been depending on microbial degradation of oligosaccharides. Endosymbiotic bacteria like Staphylococcus sciuri, Brevibacterium species and Staphyloccocaceae bacterium were isolated from pea aphid honeydew, and Enterococcus species were isolated from fava bean leaves, in an effort to determine the microbial diversity in pea aphid honeydew. These microbes may be playing a key role in assisting T. podisi in honeydew utilization and this aspect needs to be explored further. To assess preferential behavior of Telenomus podisi when exposed to overwintering conditions in an environmental chamber, artificial refuges of paper of varying geometries were constructed and presented as potential overwintering habitats in addition to Podisus maculiventris egg shells. Leaf-litter and tree bark sampling was also done to determine preferred natural overwintering sites for parasitoids in general, and scelionids in particular. Results showed that T. podisi preferred hanging upside down from refuges, avoided tight spaces but showed no preference for any particular refuge construction material. Parasitoids also showed no preference for how far away from the edge of horizontal shelters they settled to become quiescent. The field study yielded higher densities of parasitoids from leaf-litter when compared to tree bark suggesting that leaf-litter might be a preferred overwintering habitat when compared to tree bark.;Field sampling of leaf-litter and tree bark was conducted to assess the overwintering refuge sites for Megacopta cribraria Fabricius (Hemiptera: Plataspidae), an invasive species threatening soybean production in the U.S. It was found that M. cribraria preferred overwintering in leaf-litter as opposed to tree bark, preferring south facing leaf-litter with highest numbers found within 5 m of forest edge. M. cribraria had no preference for tree diameter or species in the mixed forest habitat. These findings may prove useful in future monitoring and management programs for M. cribraria.;Therefore, through better understanding of the ecological intricacies affecting parasitoids and pests, the information from these studies could be used to improve the potential for conservation biological control of pentatomids and plataspids.