Evaluating the effects of short-term low temperature on the growth and development of Trichopria drosophilae based on the age-stage two-sex life table.

Background: The effects of low temperatures on parasitic wasps are crucial for maintaining farmland biodiversity and enhancing biological control, especially given the implications of global warming and frequent extreme cold events.

Methods: We studied the effects of different low temperatures (-8 ± 1 °C, -4 ± 1 °C, 0 ± 1 °C, 4 ± 1 °C, and 8 ± 1 °C) on the mating frequency and duration of male adults of Trichopria drosophilae and the number of pupae beaten by female adults, and constructed the age-stage two-sex life table of T. drosophilae.

Results: This study found that male T. drosophilae adults exposed to low temperatures for 12 h significantly altered their mating behavior, peaking between 15:00 and 17:00. As the temperature dropped during the exposure, both the mating frequency of T. drosophilae and the duration of pupal beating were affected. The survival rate of female adults dropped from 39.55% at 8 °C to just 21.17% at -8 °C. Low-temperature treatment shortened the development period and lifespan for T. drosophilae adults. They developed 4.71 days faster and had a total lifespan that was 10.66 days shorter than those in the control group after being exposed to -8 °C. Furthermore, the average number of eggs laid by females at -8 °C was 4.46 less than that at 8 °C and 6.16 less than that in the control group, which laid an average of 21.55 eggs. The net reproductive rate (R₀) of T. drosophilae decreased with lower temperatures, reaching a low of 23.64 at -8 °C. Conversely, the intrinsic growth rate (r_m) actually increased as temperatures dropped, with the lowest value being 0.21 at -8 °C.

Conclusions: The findings indicate that short-term exposure to low temperatures hampers the growth and population increase of T. drosophilae, thereby reducing their effectiveness as biological control agents.