Susceptibility of Schistocerca gregaria (Forskal) and Euprepocnemis plorans (Charpentier) to Metarhizium anisopliae var. acridum (Metchnikoff) Soroken, Beauveria bassiana (Bals.) Vuill. and Nosema locustae Canning

Effects of the fungi; Metarhizium anisopliae var. acridum (Metchnikoff) Soroken (=Metarhizium flavoviride) Beauveria bassiana (Bals.) Vuill. and the microsporidian Nosema locustae Canning on the acridiids Schistocerca gregaria (Forskal) and Euprepocnemis plorans (Charpentier) were studied in the laboratory. The three pathogens were tested at doses of 10(3), 10(4), 10(5) and 10(6) spores/nymph. Mortalities were subjected to probit analysis to study the dose and time mortality response. The results showed that M. anisopliae var. acridum was the most virulent pathogen to the 3(rd) nymphal instar of S. gregaria and E. plorans followed by B. bassiana, then N. locustae, where the LD(50)s for desert locust at the 7(th) day were 3.5X10(7), 7.4X10(8) and 3.0X10(10) spores/nymph, on the 14(th) day were 4.5X10(4), 7.0X10(5) and 1.2X10(8) spores/nymph and on the 21(st) day were 3.6X10(3), 3.5X10(5) and 1.1X10(5) spores/nymph, after infection with M. anisopliae, B. bassiana and N. locustae, respectively. In case of E. plorans, the LD(50)s on the 7(th) day were 3.5X10(7), 1.6X10(8) and 3.7X10(9) spores/nymph, on the 14(th) day were 2.3X10(4), 7.0X10(5) and 3.3X10(6) spores/nymph on the day 21(st) were 1.3X10(3), 8.7X10(4) and 1.3X10(5) spores/nymph, after infection with the same respective pathogens. Concerning the speed of kill, M. anisopliae was the fastest. pathogen in its action followed by B. bassiana, then N. locustae at LT(50) values bases. The LT(50) values of M. anisopliae, B. bassiana and N. locustae when applied to S. gregaria at the dose 103 were 24.66, 36.39 and 51.26 days, at the dose 10(4) were 16.37, 21.84 and 27.05 days, at the dose 10(5) were 11.76, 17.85 and 20.13 days and at the dose 10(6) were 10.76, 13.59 and 17.40 days, respectively. When applied to E. plorans, the LT(50) values of M. anisopliae, B. bassiana and N. locustae at the dose 10(3) were 19.72, 36.61 and 40.47 days, at the dose 10(4) were 14.90, 23.24 and 23.54 days, at the dose 10(5) were 11.76, 17.85, and 20.12 days, and at the dose 10(6) were 10.43, 13.47 and 16.08 days, respectively. The fungi M. anisopliae var. acridum and B. bassiana showed significant prolongation to infected 3(rd) nymphal insatr of both insect species. The entomopathogens lead to significant prolongation in duration of infected 4(th) and 5(th) nymphal instars. M. anisopliae var. acridum caused the longest prolongation to all nymphal instar durations followed by B. bassiana then N. locustae. The pathogens also caused significant reduction in number of egg pods and number of eggs per pods, in addition they caused significant prolongation in the preovipositional period and the period between each egg pod. They also induced significant reduction in the adult longevity. The most effective pathogen on the fecundity of S. gregaria and E. plorans was M. anisopliae var. acridum followed by B. bassiana then N. locustae.