Effect of successive transplantation in rice on the virulence of Metarrhizium anisopliae (metsch.) sorokin against Deois flavopicta

Abstract

The effect of succesive transplantation in a rice medium on the virulence of Metarrhizium anisopliae (Metsch.) Sorokin was studied through a biossay with nymphs of Deois flavopicta Stal 1854 (Homoptera, Cercopidae). The strain E₉, from Espirito Santo state, Brazil, and an isolate J-71, obtained from a natural infection in Deois flavopicta, in Jataí, GO, Brazil, were tested. In both cases spores were collected from artificially infected spittlebugs to obtain the first generation in rice medium. It was demonstrated that the maximum degree of virulence was attained in the third generation of fungus. In this generation, the percentage of dead nymphs, due to Metarrhizium anisopliae, ranged from 65% for strain E₉ to 76.6% for the J-71 isolate. After three generations in a rice medium, rapid reduction was observed in the nymphal infection rate. After 10 generations, the average percent infection was 11.3 for strain E₉ and 16.7 for J-71. Insects started to die two days after the fungal inoculations; superficial mycelial growth began after three to four days, and sporulation started from five to seven days after inoculation.