Effect of temperature and humidity on performance of Aprostocetus brevipedicellus (Hymenoptera: Eulophidae)

Aprostocetus brevipedicellus Yang and Cao (Hymenoptera: Eulophidae) is a gregarious egg parasitoid of lepidopterous pests and a promising biological control agent for many forest pests. To establish optimal mass rearing conditions for A. brevipedicellus, we evaluated its biological and population parameters, as well as offspring fitness, when reared on eggs of Antheraea pernyi Guérin-Méneville (Lepidoptera: Saturniidae). The parasitoid was exposed to 5 constant temperatures (16, 20, 24, 28, and 30 °C) at 65% to 75% relative humidity (RH) and 4 humidity levels (30, 50, 70, and 90 ± 5% RH) at 23 to 25 °C. The results showed that the 24 °C and 70% RH treatment elicited the optimal reproductive performance in A. brevipedicellus, yielding both the highest fecundity and net reproduction rate (R0) among all tested temperature and humidity treatments, 13% to 50% and 19% to 74% higher, respectively, than those under the remaining treatments. Meanwhile, the highest offspring emergence rate and the lowest number of dead parasitoids per host egg were also observed at 24 °C and 70% RH treatment. Furthermore, A. brevipedicellus exhibits considerable tolerance to humidity, completing its life cycle at 24 °C across the entire tested range (30% to 90% RH). However, its thermal tolerance was more limited. The larvae survived in a state of arrested development at 16 °C, and although adults developed at 32 °C, they failed to emerge from host eggs. These findings indicate that 24 °C and 70% RH are the optimal conditions for the mass production of A. brevipedicellus.