ABSTRACT Fungal virulence is multifaceted and dependent on multiple factors including the pH of the spore suspension. In this study, we accessed effects of six pH values of Beauveria bassiana, and Metarhizium anisopliae medium for the growth, sporulation, and mortality on sugarcane stalk borer Diatraea saccharalis. The culture of fungi was performed onplates containing the PDA (Potato Dextrose Agar) medium. Virulence was tested in D. saccharalis larvae distributed in four replicates of 15 larvae. To evaluate the performance of the isolates, they were grown at different pH values in an artificial chitin medium to confirm the degradation capacity of the fungi at each pH. No significant difference was observed for the sporulation at pH ranged from 4 to 9 for both fungi. In the mortality assay, larval mortality was higher at pH 7 and 8 for both fungi, reaching 87% for B. bassiana and 81% for M. anisopliae.

RESUMO O silício é indutor de resistência de plantas a artrópodes pragas, constituindo-se em promissora estratégia para o manejo integrado. O trabalho objetivou avaliar o efeito do silício nos aspectos biológicos, reprodutivos e populacionais do ácaro-rajado nas gerações parental e F1 em morangueiro. As plantas receberam aplicações de silicato de potássio, nanossílica e água. Fêmeas do ácaro-rajado foram confinadas sobre os discos foliares de morangueiro para oviposição e, após a eclosão, larvas foram observadas até a emergência dos adultos. Destes, casais foram formados para avaliação da pré-oviposição, oviposição, longevidade e fecundidade, com estimativa da taxa líquida de reprodução, taxa intrínseca de aumento, razão finita de aumento e tempo médio de geração. O silício prolongou a duração de algumas fases imaturas do ácaro-rajado nas gerações parental e F1, mas não afetou a duração total do ciclo de desenvolvimento da praga. Os períodos de pré-oviposição, oviposição e longevidade da geração parental e a longevidade e fecundidade da geração F1 do ácaro-rajado foram afetados negativamente pelo silicato de potássio e nanosilicato. Os parâmetros populacionais da geração parental do ácaro-rajado indicam que a nanossílica pode diminuir a população desta praga a longo prazo.

ABSTRACT Silicon is an inducer of plant resistance to arthropod pests, being a promising strategy for integrated management. The aim of this study was to evaluate the effect of silicon on biological, reproductive and population aspects of parental and F1 generations of the two-spotted spider mite on strawberry plants. Potassium silicate, nanosilica and water were applied to the plants. Two-spotted spider mite females were confined to strawberry leaf disks for oviposition and, after hatching, larvae were observed until the emergence of adults. Once adults had been obtained, couples were formed in order to evaluate pre-oviposition, oviposition, longevity and fertility, with an estimated net reproduction rate, intrinsic rate of increase, finite rate of increase and the necessary time for doubling the generation. Silicon prolonged the duration of some immature stages of the mites in parental and F1 generations, did not affect the duration of the whole biological cycle, though. The periods of pre-oviposition, oviposition and longevity of the parental generation and the longevity and oviposition of F1 generation of the two-spotted spider mite were negatively affected by potassium silicate and nanosilica. The population parameters of the parental generation of the mites indicated that nanosilica is able to lead to a long-run decrease of this pest population.