Infection with pathogenic fungi is a major threat to the mass production of the parasitoid wasp Habrobracon hebetor: 20 generations under surveillance

Abstract

Pathogen infection is one of the most important challenges threatening the success of mass rearing of natural enemies either in insectaries or in augmentative biological control programs. In this investigation, we studied the biological and population growth parameters of a naturally infected colony of the parasitoid wasp Habrobracon hebetor (Say) (Hymenoptera: Braconidae) over 20 generations (G1_inf − G20_inf) of rearing on Ephestia kuehniella (Zeller) (Pyralidae: Lepidoptera) under laboratory conditions. Based on morphological characteristics and ITS sequences, two types of fungal colonies were isolated from the diseased females and identified as Thermothielavioides terrestris and Aspergillus flavus. The results showed that although no significant differences were found in the female longevity and fecundity of H. hebetor on E. kuehniella up to G15_inf, the duration of the immature period was extended as the number of generations increased. In addition, the intrinsic rate of increase (r) and finite rate of increase (λ) had no significant differences up to G8_inf. The net reproductive rate (R₀) of G15_inf had no significant differences with G2_inf, G8_inf, and G10_inf. On the other hand, in G15_inf, R₀ was significantly higher than G4_inf, G6_inf, and G20_inf. The findings underscore the negative impact of fungal infection on population growth parameters compared with uninfected population. This study showed that naturally fungal infection of the parasitoid affected the population growth and life table parameters through mass rearing, compared and discussed with the healthy parasitoid.