Thermal Requirements of Ooencyrtus submetallicus (Hym.: Encyrtidae) and Telenomus podisi (Hym.: Platygastridae) Parasitizing Euschistus heros Eggs (Hem.: Pentatomidae)

SIMPLE SUMMARY: The brown stink bug, Euschistus heros, is the most abundant species infesting Brazilian soybean crops, causing significant yield losses. This stink bug is controlled with chemical insecticides, although the use of biological control with the egg parasitoids Ooencyrtus submetallicus and Telenomus podisi is increasing. Our objective in this study was to evaluate the development of O. submetallicus and T. podisi in E. heros eggs at different temperatures, and to estimate the number of annual generations for seven representative soybean-producing regions in Brazil. In the comparative biology study, the sex ratio and individuals per egg were higher for O. submetallicus in all regions. In the study of thermal requirements, the temperatures of 16, 19, 22, 25, 28, 31, and 33 °C were tested. The base temperature (Tb) for O. submetallicus and T. podisi was found to be 9.3 and 6.7 °C, and the thermal constant (K) was 336.9 and 272.7 degree-days, respectively. The average number of annual generations was estimated from the average temperatures of the last ten years in each region; based on these results, both parasitoids presented a higher number of generations than the host in all regions. O. submetallicus and T. podisi have the same ability to parasitize and develop in the eggs of E. heros under the conditions studied; in addition, both exhibited development and satisfactory parasitism at temperatures between 19 and 31 °C. The development of the two parasitoids was faster than E. heros, and the number of generations was higher for the seven studied localities. ABSTRACT: Temperature is one of the abiotic factors that strongly influences the biology and behavior of insects. In this study, we assessed the development of egg parasitoids Ooencyrtus submetallicus and Telenomus podisi parasitizing Euschistus heros eggs at different temperatures, and estimated the average number of generations for seven representative soybean-producing regions in Brazil. A comparative biology study was conducted, where the percentage of parasitism and emergence, life cycle duration (egg–adult), and longevity were found to be similar between O. submetallicus and T. podisi. The sex ratio and the number of individuals emerged from parasitized egg were higher in O. submetallicus in all regions. In the study of thermal requirements, temperatures of 16, 19, 22, 25, 28, 31, and 33 °C were tested. O. submetallicus and T. podisi developed at temperatures between 16 and 31 °C. The base temperature (Tb) for O. submetallicus and T. podisi was 9.3 and 6.7 °C, respectively; the thermal constant (K) was 336.9 and 272.7 degree-days, respectively. The estimated average number of annual generations of both parasitoids was higher than the host. O. submetallicus and T. podisi have the same ability to parasitize and develop in eggs of E. heros under the conditions studied. Both parasitoids exhibited satisfactory development and parasitism at temperatures between 19 and 31 °C. The development of both parasitoids was faster than their host, and the number of generations was higher for the seven studied localities.