Effects of larval age on mortality of Monochamus alternatus Hope (Coleoptera: Cerambycidae) after application of nonwoven fabric strips with Beauveria bassiana.

Abstract

During field applications of Beauveria bassiana for control of Monochamus alternatus larvae living in dead pine trees, differences of mortalities by application date could not be analyzed due to variability in timing of oviposition. To solve this problem, pine logs with eggs of the same age were obtained by exposing logs to female beetles for one day in a screened cage in July or August. Nonwoven fabric strips impregnated with B. bassiana cultures were applied to the logs in September. Infection rate by B. bassiana was higher among larvae from eggs laid in August compared with those from eggs laid in July. Among the logs oviposited on the same day, the infection rate was higher in those with 4 strips/2 m than those with 1.5 strips/2 m. The results of the experiment showed that control of M. alternatus by applying nonwoven fabric strips with B. bassiana was more effective when the fungus was applied to young larvae located under the bark instead of older larvae further within the wood.