Telenomus podisi Parasitism on Dichelops melacanthus and Podisus nigrispinus Eggs at Different Temperatures

Dichelops melacanthus (Dallas) (Heteroptera: Pentatomidae) is the most important stink bug species that feeds on maize in South America, and it is frequently controlled with chemical pesticides. As an alternative, more sustainable management strategies can be applied, among which the egg parasitoid Telenomus podisi Ashmead (Hymenoptera: Scelionidae) stands out. However, T. podisi can have the undesired effect of parasitizing the predator and biocontol agent Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae). Therefore, the study of T. podisi parasitism on eggs of both D. melacanthus and P. nigrispinus is of theoretical and practical interest. Individual 48-h-old parasitoids were offered a card with host eggs. Parasitism was allowed for 24 h at 25 ± 2 °C. Afterwards, the eggs were exposed to temperatures of 15, 20, 25, or 30 ± 2 °C to test the effects of temperature on the development of immature stages of the parasitoid (egg-to-adult period, emergence (%), and sex ratio). In addition, eggs were offered on a daily basis to parasitoid females exposed to 15, 20, 25, or 30 ± 2 °C. Parasitism was allowed for 24 h before eggs were replaced with fresh ones (≤ 24 h) and stored at 25 ± 2 °C until emergence. This allowed us to study the effects of temperature on adult parasitism capacity (daily parasitism, accumulated percentage of parasitism, parental female longevity, and total number of parasitized eggs per female). Our results show that temperature significantly influenced duration of the egg-to-adult period, emergence, sex ratio, total number of parasitized eggs, and parental female longevity of T. podisi on both host species. Development time of the parasitoid was reduced with increasing temperature. Emergence above 80% was observed at temperatures of 20 and 25 °C in eggs of D. melacanthus, and at 20, 25, and 30 °C in eggs of P. nigrispinus. In both hosts, the ratio of females (sex ratio) was highest at the lowest temperature (15 °C). In both host species, daily parasitism and total number of parasitized eggs decreased with time, and longevity of females was inversely proportional to an increase in temperature. These results allow us to conclude that extreme temperatures of 15 and 30 °C are not favorable for T. podisi parasitism, even though parasitism was still observed. Therefore, in regions where those extreme temperatures are common, additional studies are necessary to explore the need for a higher number of parasitoids for successful field releases. Even though the release of T. podisi in the field may negatively impact the predator P. nigrispinus, it is problaly still safer than the use of chemical insecticides, which would be the alternative measure to T. podisi in the control of stink bugs.