Effects of cold storage on the fitness of Bracon adoxophyesi, as an important parasitoid of palm pests.

Abstract

The cold storage of biological control agents, such as parasitoids, is a valuable method utilised in mass rearing to ensure the availability of sufficient individuals when needed. This study evaluated the effects of storage temperatures of 9°C and 12°C, along with incubation periods of 7, 14, 21, 28, and 35 days, on the biological fitness of Bracon adoxophyesi Minamikawa (Hymenoptera: Braconidae). The results demonstrated that the survival rates of adult wasps exceeded 90.0% after being stored at both 9°C and 12°C for 35 days. At these temperatures, female wasps exhibited their longest lifespan at 14 days, whereas male longevity decreased progressively from 7 to 35 days. The parasitism rates observed were 43.0% at 9°C and 46.0% at 12°C after 7 days of refrigeration, with a subsequent reduction noted after 35 days. The fecundity of parasitic wasps decreased with the extension of storage time, but no significant difference was found in total egg production within 28 days of storage. Additionally, cold storage did not significantly affect the survival of the offspring; however, the proportion of females among the raised offspring was higher than in the control group. In comparing fitness parameters to the control, wasp vitality was notably higher after 21 days of storage at 9°C or 14 days at 12°C, indicating that these combinations of temperature and time are optimal. The findings of this study serve as a reference for optimising cold storage techniques and facilitating the large-scale application of B. adoxophyesi.