Thermal requirements and parasitism capacity of Trissolcus brochymenae (Ashmead)(Hymenoptera: Scelinoidae) under constant and fluctuating temperatures, and assessment of development in field conditions

In order to understand the relative importance of Trissolcus brochymenae, a common egg parasitoid of the predatory stinkbug Podisus nigrispinus in areas where this predator is released, the thermal requirements and developmental periods (egg to adult) at constant (17, 20, 25, 28 and 32 degrees C) and fluctuating (10-20, 13-23, 15-25, 17-27, 20-30 and 25-35 degrees C) temperatures, and the effect of constant and fluctuating temperatures systems on the longevity and parasitism capacity of T. brochymenae were investigated. Based on thermal requirements of the parasitoid and field day/night temperature variation in the regions where P. nigrispinus was released, we calculated monthly and yearly number of generations of the parasitoid. Parameters of biological and thermal requirements of T. brochymenae were not affected when the insects were reared under constant or fluctuating temperatures. It was shown that males have a shorter developmental period and lower thermal requirements than females. The lowest parasitism capacity and shortest longevity of T. brochymenae were observed under fluctuating temperature regimes of 10-20 degrees C and 25-35 degrees C. A higher parasitism capacity was obtained under a 20-30 degrees C regime (96.0 +/- 33.6 offspring per female), while longevity was longer at a constant temperature of 27 degrees C (17.6 +/- 0.6 days). T. brochymenae showed a continuous development during all seasons through the year under field conditions, accomplishing 2.7, 2.4, 2.9 generations per month in the CAF, Pains, and Refloralje areas. An average of 26.4 and 25.8, 25.8 and 25.3, and 24.7 and 23.6 generations per year under constant and fluctuating temperatures systems was estimated for the CAF Pains, and Refloralje areas, respectively. No significant difference between thermal systems in each area was observed; however, a significantly smaller number of generations per year were estimated to occur in the Refloralje area. Implications of these results for the forecasting of parasitoid population development and its impact on the host stinkbug predator are discussed.