Generation-Dependent Functional and Numerical Responses of a Naturally Fungus-Infected Colony of Habrobracon hebetor (Hymenoptera: Braconidae) Reared on Ephestia kuehniella (Lepidoptera: Pyralidae) in Iran

Abstract

Abstract The functional and numerical responses of Habrobracon hebetor (Say) were assessed over 30 sequential generations (G) on different densities (2, 4, 8, 16, 32, 64, and 128 fifth-instar larvae) of the Mediterranean flour moth, Ephestia kuehniella (Zeller). Seven tested generations (G2inf, G4inf, G6inf, G8inf, G10inf, G15inf, and G30inf) had already been naturally infected by a fungus species, whereas only the second generation (G2) had the colonies of both infected (G2inf) and uninfected (G2uninf) individuals. All infected generations, as well as the uninfected generation, showed a Type III functional response. A high variation was found in the handling times (Th) of the parasitoid through 30 sequential generations, and G10inf had the longest handling time. The shortest handling time and the maximum estimated attack rate (T/Th) were observed in G2inf. No significant difference in terms of the number of parasitized hosts was found among all infected generations, as well as between G2inf and G2uninf. Although the handling times in G2inf and G2uninf were close to each other, the attack coefficient of G2uninf was more than that of G2inf. The attack coefficient and handling time of infected generations increased from G2inf to G10inf and then decreased in the higher generations. The most plausible parameters of functional response of infected generations were observed in Ginf. A negative relationship between eggs laid and host densities was observed in the infected generations (G2inf, G4inf, G6inf, G8inf, and G10inf). G2uninf and, among infected generations, Ginf were the best generations for practical utilization in inundative release programs.