Impacto de priori xtra® sobre Nomuraea rileyi em lagartas desfolhadoras

Abstract

The population outbreak of caterpillar in soybeans has been linked with entomopathogenic elimination of fungi by fungicides. Many experiments were conducted to understand the effect of fungicides Azoxystrobin + Cyproconazole on Nomuraea rileyi. The experiments were: (a) N. rileyi activity time; (b) effect of fungicide application on N. rileyi; (c) the natural occurrence of N. rileyi; and (d) the spectrum of action of N. rileyi on soybean caterpillars. Anticarsia gemmatalis mortality achieved 100% at 48 hours when N. riley was inoculated in powder form. N. rileyi in powder form showed higher time activity in comparison to application of N. rileyi in liquid form. Fungicide application on N. rileyi caused a delay on A. gemmatalis mortality. However, when evaluation was later the mortality of A. gemmatalis by N. rileyi was not affected. The occurrence of N. rileyi in caterpillars was different among local sampled, and it was mainly associated with the weather conditions. N. rileyi showed to be entomopathogenic to A. gemmatalis, Spodoptera frugiperda, Helicoverpa armigera and Chrysodeixis includens, however, the mortality ranged among species. The major factor that impacted on non-occurrence of N. rileyi in some years may be the weather conditions, rather than fungicide applications. Therefore, fungicides were not the main cause of non-occurrence of N. rileyi and therefore it was not the main cause of caterpillars outbreaks in soybean.