Effect of two dosages of Metarhizium anisopliae var. acridum against Rhammatocerus schistocercoides Rehn.

The fungs Metarhizizium anisopliae var. acridum, strain CG 423, was tested under fiel conditions against the gregarious grasshopper Rhannatocerus schistocercoides (Rehn) (Orthoptera: Acrididae). Conidia formulated in a rancemic mixture of soybean oil and kerosene were sprayed under field conditions using na ultralow-volume hand-held atomizer Ulva Plus adjusted to deliver 2.9 L/há. Bands composed of 2 nd instar nymphs were treated eitheir 5.0x 1012nor 1.0x1013 viable conidia/ha. The number of insects in each band was estimated at day one following spraying and by the field trial ( 15 to 16 days pos-treatment). Reductions in population size reached, in average, 65.5% for bands treated with the higher and lower dosage, respectively. For both dosages, total mortality rates of collected at two days post-application, and kept in cages for 14 days under lab conditions, showed no significant differences as cmpared to that obtained with insects were fed donative grasses sprayede on the field with 1. 0x 1013 viable conidia/há. Mortality levels of the nymphs on grasses collected two and days post-application were not affected when compared to nymphs fed on grasses collected immediately following application