Field trial with the entomopathogenic fungus Metarhizium anisopliae var. acridum against bands of the grasshopper Rhammatocerus schistocercoides in Brazil

The efficacy of a mycoinsecticide formulated in vegetable oil was tested in Brazil against the grasshopper Rhammatocerus schistocercoides. A set of ex periments was conducted in the Chapada dos Parecis region (Mato Grosso stat e), a permanent zone of outbreaks for this pest. Experiments were performed in zones of natural vegetation, against grasshopper bands in the third nym phal instar. Three nymphal bands were treated with a mycoinsecticide formul ation based on conidia of the entomopathogenic fungus Metarhizium anisoplia e var. acridum (=M. flavoviride), strain CG 423. Three non-treated bands we re used as control. The application was made with the aid of a hand-held UL V sprayer adjusted to deliver 2 l of the formulation ha(-1), each containin g 1 X 10(13) conidia. Treatments were limited to the surface of the grassho pper bands and their immediate borders (5-10 m). The efficacy of the mycoin secticide was evaluated through band survival after treatment (grasshopper numbers, surface, density, behaviour and daily movement of the band), allow ing the insects to move freely in their natural environment. Insects were r egularly surveyed and maintained in the laboratory, allowing estimates of t he infection rate. Field and laboratory studies showed a clear effect of th e product 10 days after treatment. At 14 days post-spraying, mortality caus ed by the mycoinsecticide in the field was approximately 88%.