Beauveria bassiana sensu lato granules for management of brown planthopper, Nilaparvata lugens in rice

Abstract

Entomopathogenic fungi have potential for controlling brown planthoppers in paddy. Currently only sprayable formulations can be applied despite the fact that granular formulations may reduce physical labor during application. Herein, granules of a Beauveria bassiana sensu lato (Balsamo) Vuillemin (Hypocreales: Clavicipitaceae) isolate were produced from a millet-based solid culture. The efficacy of the granules to control brown planthoppers, Nilaparvata lugens (Stal) (Hemiptera: Delphacidae), was determined by applying them to water surrounding rice plants in the laboratory and then infesting the plants with brown planthoppers. In a spray-mediated bioassay to select the most virulent of four B. bassiana s.l. isolates, ERL836 was the most virulent and caused minimal damage to rice plants. Dropping the ERL836 granules on water provided similar control to spraying the conidia. In the laboratory ERL836-colonized millet granules were applied to the water and simultaneously infested with brown planthoppers. The granular treatment had 87.7 % control efficacy 15 days post-application and etofenprox 0.5 % granules had 94.6 % efficacy. ERL836 colonized the surface of the water and brown planthoppers underwent mycosis three and 15 days post-application. Mycelial growth on the stems of rice plants was observed using a B. bassiana s.l. mutant that expresses an enhanced green fluorescence protein. Applying millet-based ERL836 granules to water can be an efficient biological strategy to manage brown planthoppers in paddy. This method is economical and requires less work than spraying the fungi directly on rice.