Abstract

The black vine weevil (BVW), Otiorhynchus sulcatus (F.) is a serious pest of nursery crops, particularly in the Pacific Northwest. The fungus, Metarhizium anisopliae (F52), has recently been registered by the U.S. Environmental Protection Agency for BVW control. The objective of this study was to determine the persistence of M. anisopliae in five common soilless potting media components (coir, fir bark, hemlock bark, peat moss and perlite), which was measured as pathogenicity against BVW larvae. Fungal granules (½ lb/yd³) were incorporated with each media component at potting and fungal persistence determined for 133 days. Experiments were performed with and without plants to determine if the presence of a plant impacted fungal persistence. Overall, the fungus persisted well in all of the potting media components tested up to 133 days post application. Persistence was somewhat lower in the first experiment, likely due to fluctuating media moisture. In the second experiment, with more stable media moisture levels, the percentage of larval infection did not drop below 88% in any media at 133 days post application. It is likely that M. anisopliae will persist well and provide high levels of BVW larval control in most of the commercial potting media used in containerized nursery production, particularly those comprised primarily of the media components tested in these studies.