Effects of temperature and host stage on the parasitization rate and offspring sex ratio of Aenasius bambawalei Hayat in Phenacoccus solenopsis Tinsley

Temperature and host stage are important factors that determine the successful development of parasitoids. Aenasius bambawalei Hayat (Hymenoptera: Encyrtidae) is a primary parasitoid of the newly invasive mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae). The effects of temperature on the parasitic characteristics of A. bambawalei have seldom been investigated. In the study, we explored the effects of temperature, exposure time, and host stage on the parasitization rate and offspring sex ratio (female to male) of A. bambawalei under laboratory conditions. The laboratory results showed that the successful parasitization rate of A. bambawalei increased with higher temperatures and older host stages. When the parasitoids were exposed to 36 °C for 24 h, the parasitization rate of female adults (52%) was nearly two times that of 3rd instar nymphs. Additionally, heat stress duration and host stage resulted in an increase in the offspring sex ratio of A. bambawalei. When A. bambawalei was exposed to 36 °C for 24 h, the offspring sex ratio increased dramatically to 81.78% compared with those exposed for 12 h, and it increased to 45.34% compared with those exposed for 16 h. The offspring sex ratio was clearly higher when the host stage was an adult female mealybug Our findings provide important guidance for the mass rearing and field releases of A. bambawalei for the management of P. solenopsis in the future.