Evaluation of Ethiopian Isolates of Entomopathogenic Fungi as Potential Biological Control Agent of the Desert Locust

Abstract

Ten native fungal isolates were collected from the different regions of Ethiopia. Six of the isolates were identified as Beauveria bassiana, one as Metarhizium anisopliae, one as Paecilomyces sp. and one as a new Beauveria sp. Eight of the tested fungal isolates showed pathogenecity to fifth instar Schistocerca gregaria. B. bassiana isolate FF and M. anisopliae isolate EE were more virulent compared to the rest. Thus two isolates were further assayed in peanut (Arachis hypogaea) and noug (Guizotia abyssinica) oil formulations, and compared with a known entomopathogen, M. anisopliae isolate ICIPE 30. The results indicated that there were
strong dose-response patterns. Peanut oil formulation enhanced infectivity of both FF and EE. Infectivity of EE was significantly (P<0.05) reduced in noug oil formulation. Comparison of virulence revealed that isolates FF and EE were more pathogenic than ICIPE 30. FF in peanut oil formulation had the lowest LCso value of 2.02xl05 conidia/ml followed by EE, 2.93xl05 and ICIPE 30 with 4.98xl05 conidia/ml. The highest mortality was achieved by FF at 1x10s conidia/ml, resulting in 50% in 4.2 days and 100% mortality in seven days. The median lethal time of the fourth, fifth larval instar and adult FF treated insects were 3.5, 4.1 and 4.8 days, respectively, indicating that the fourth larval instar is more susceptible. FF and EE grew at a temperature range of 24°C and 37°C, with peaks at 24°C and 28 C for FF and 28°C for EE. Malt extract agar favored growth and sporulation of FF, whereas EE grew and sporulated faster
on sabouraud dextrose agar. Germination of both isolates was significantly (P<0.05) higher in peanut oil formulation than in noug oil.