Prospects of entomopathogens in post-harvest integrated pest management

In these exploratory experiments, entomopathogenic nematodes and fungi were investigated for the management of the populations of postharvest insect pests. Nematodes were screened for pathogenicity to Plodia interpunctella (Hübner), while nematodes and fungi were investigated for virulence to the maize weevil, Sitophilus zeamais (Motschulsky). Adults and larvae of P. interpunctellea were screened for susceptibility to the following six nematodes: Heterorhabitis bacteriophora Poinar (HP88, Lewiston and Oswego strains); H. indica Poinar, Karunakar and David (Homl strain); H. marelatus Liu and Berry (Point Reyes strain); H. megidis Poinar, Jackson, and Klein (UK211 strain); and H. zealandica Poinar (NZH3 strain). The nematodes that had the highest virulence to larvae and adults of P. interpunctellea were H. indica, H. megidis, and H. marelatus. Six strains of nematodes were studied, namely H. bacteriophora, H. indica, H. georgiana (K22), Steinernema feltiae SN and S. carpocapsae. All strains of fungi, Beauveria bassiana (GHA) and Metarhizium brunneum (F52) were evaluated for infectivity to adults of S. zeamais. The two strains of Steinernematidae nematodes and a strain of fungus, B. bassiana were found to cause significant mortality of the weevils compared to the rest of the entomopathogens and the control. To demonstrate the practical application of entomopathogens, wettable dust of B. bassiana were dispensed on jute bags after which weevils were exposed to the treated surfaces for 30 min. The exposed weevils recorded between 90 to 100% mortality 14-d after exposure. Additional study demonstrated that the parasitoid, Habrobracon hebetor (Say) (Hymenoptera: Braconidae) could be integrated with entomopathogenic nematodes. These experiments demonstrate the potential usefulness of entomopathogens in the management of stored product Lepidopteran and Coleopteran pests.