Sublethal effects of Metarhizium anisopliae on life table parameters of Habrobracon hebetor parasitizing Helicoverpa armigera larvae at different time intervals

摘要

The ectoparasitoid wasp, Habrobracon hebetor Say and the entomopathogenic fungus, Metarhizium anisopliae (Metsch.) Sorokin are biocontrol agents attacking larval stages of Helicoverpa armigera (Hubner). Life table parameters of H. hebetor were studied on H. armigera third instar larvae previously (0, 24, 48, and 72 h) infected with a sublethal concentration (LC30) of M. anisopliae (isolate M14). Fungal infection adversely affected life table parameters of H. hebetor depending on the host postinoculation time for parasitoid release. The entropy values showed the age-specific survivorship (l(x)) curves of type 1 at = 24 h treatments. The highest and lowest intrinsic rates of increase (r(m)) were 0.223 and 0.109 for control and 72 h treatment, respectively. Statistically different variations were observed for r(m) values when post-exposure time was longer than 24 h. Our findings highlight appropriate introduction times of H. hebetor in combination with M. anisopliae (isolate M14) for successful integrated management of H. armigera.