Steinernema australe Enhanced Its Efficacy against Aegorhinus nodipennis (Coleoptera: Curculionidae) Larvae in Berry Orchards after an Artificial Selection Process

Abstract

The entomopathogenic nematode (EPN) Steinernema australe was isolated from Isla Santa Magdalena in Chile and identified as a good alternative for controlling Aegorhinus nodipennis (Coleoptera: Curculionidae) larvae. This weevil is native to the south of Chile and some regions in Argentina, causing the decline and ultimate death of plants in berry orchards. The major problem brought about by the weevil is caused by the larvae, which spend between nine and eleven months below ground, feeding inside the roots of the plants. This study seeks to increase S. australe’s efficacy through an artificial selection process using an odor stimulus. We selected infective juveniles (IJs) that followed the stimulus in order to reach larvae at a depth of 30 cm to achieve this objective. Larvae infected with selected IJs and IJs from the original stock were compared under laboratory, greenhouse, and field conditions. The results showed a 20% increase in the efficacy of selected IJs compared with IJs from the original stock. We observed a higher proportion of selected IJs that reached the larvae faster during the first four days post-application. Moreover, larvae treated with selected IJs were depleted, with a mix of nematode stages emerging from the cadaver. Finally, a potential trade-off with regard to the recycling of nematodes into the soil is proposed.