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.
ABSTRACT
Halyomorpha halys (Stål), or brown marmorated stink bug (BMSB), has become a major pest and nuisance for both agricultural growers and homeowners since its arrival in North America and Europe. The nutritional ecology of BMSB is important for understanding its life history and rearing requirements. However, little is known about the nutritional status of wild populations, especially in the U.S. This research monitored the nutrient status of nymphal and adult BMSB collected from English holly in western Oregon. We measured their weight, nutrient index (weight/(prothorax × width)³), lipid, glycogen and sugar levels and egg load from Mayâ»September/October. First, glycogen and sugar levels of adults were often lowest sometime in June-August with a general increase by September. Meanwhile, their lipid levels varied without a discernible trend. Second, adult females had few eggs in May, with the highest egg load in June and July, and no eggs by September. Lastly, first and second nymphal instars were found in June, and fourth and fifth instars in September. Because nothing is known about the nutrient levels of nymphs, the reported values from this survey can assist future research on physiological responses of BMSB to treatments or environmental impacts in the field.
ABSTRACT
Temperature-based degree-day models describe insect seasonality and to predict key phenological events. We expand on the use of a temperature-based process defining timing of reproduction through the incorporation of female reproductive physiology for the invasive pentatomid species Halyomorpha halys, the brown marmorated stink bug. A five-stage ranking system based on ovary development was able to distinguish between the reproductive statuses of field-collected females. Application of this ranking method described aspects of H. halys' seasonality, overwintering biology, and phenology across geographic locations. Female H. halys were collected in the US from NJ, WV, NC, OR, and two sites in PA in 2006-2008 (Allentown, PA only) and 2012-2014. Results identify that H. halys enters reproductive diapause in temperate locations in the fall and that a delay occurs in developmental maturity after diapause termination in the spring. Modification of the Snyder method to identify biofix determined 12.7-hr photoperiod as the best fit to define initiation of reproduction in the spring. Applying the biofix, we demonstrated significant differences between locations for the rate at which the overwintering generation transition into reproductive status and the factors contributing to this difference require further study. For example, after including abiotic variables influencing development such as temperature and photoperiod (critical diapause cue), reproduction occurred earlier in OR and for an extended period in NJ. This data describe a method to investigate insect seasonality by incorporating physiological development across multiple regions that can clarify phenology for insects with overlapping generations.
