EFFECTS OF BEAUVERIA BASSIANA ISOLATES ON SITOPHILUS ORYZAE L. UNDER IN VITRO CONDITIONS

Stored grain insect pests can reduce weight, quality, seed viability and commercial value of stored grains. Management of these pests mainly rely on synthetic insecticides and fumigants. Negative effects of these pesticides have urged the researchers to develop alternative and environmentally friendly management strategies such as microbial control. Microbial control strategy uses living organisms called microbial control agents and entomopatho-genic fungi are one of these agents. The objective of the current study was to assess the efficacy of ento-mopathogenic Beauveria hassiana isolates (F-52, F-53 and F-56) against rice weevil (Sitophi/us oryzae) and the damage they cause to stored wheat grains. Morphological analysis of the isolated fungi and molecular identification was determined using PCR technique. The efficacy of fungal isolates against S. oryzae was tested by wheat grain dipping method. Wheat grains were dipped into different conidial concertation (1 x 103, 1 x 105, 1 x 107, 1 x 108, 1 x 109 conidia/ml) for 1 hour. The seeds were then dried and transferred to glass vial containing ten adult insects. The vials were incubated at 25±1 °C temperature and 75% relative humidity for 11 days. Thereafter, the treated adult insects were checked for mortality after 1st, 3rd, 5th, 7th, and 9th days of incubation. Dead insects were transferred to moist sterile 90 mm glass Petri dishes to determine the mycosis rate. The cumulative mortality in adults 9 days after exposure to isolates of B. hassiana ranged between 22% and 94%,31%and 100%, and 14% and 86% for different concentrations of F-52, F-53, and F-56, respectively. The highest mortality rate (100%) was obtained after 9 days incubation period with F-53 isolate at 1 x 108 conidia/ml concentration. The highest mycosis rate (95%) was obtained at the end of the 14th day with F-52 isolate in 1 x 109 conidia/ml, which was followed by F-53 (93%) and F-56 (82%) isolates. The results indicated that these isolates caused high mortality and exhibited higher mycosis rate. Further storage trial should be conducted, particularly with these isolates to see their in vivo performances.