Persistence of Metarhizium Anisopliae Incorporated into Soilless Potting Media for Control of the Black Vine Weevil, Otiorhynchus Sulcatus in Container-Grown Ornamentals

Authors: Bruck, Denny; Donahue, Kelly

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2007
Publication Date: 6/1/2007
Citation: Bruck, D.J., Donahue, K.M. 2007. Persistence of metarhizium anisopliae incorporated into soilless potting media for control of the black vine weevil, otiorhynchus sulcatus in container-grown ornamentals. Journal of Invertebrate Pathology. 95: 146-150.

Interpretive Summary: The black vine weevil (BVW), Otiorhynchus sulcatus (F.) is a serious pest of nursery crops, particularly in the Pacific Northwest. The insect killing fungus, Metarhizium anisopliae (F52), has recently been registered by the US Environmental Protection Agency for BVW control. The objective of this study was to determine the persistence of M. anisopliae, measured as its ability to kill BVW larvae, in soilless potting media at six wholesale nursery locations across the Willamette Valley, Oregon. The fungus was incorporated into media at potting and fungal persistence determined over two growing seasons (2004 and 2005). Media was sampled from the inner core and outer ring of each pot. Metarhizium anisopliae persisted in the potting media over the duration of the experiment (two growing seasons) with 50-60% of the larvae exposed to fungal inoculated potting media becoming infected. The percentage of larval infection differed significantly between media sampled from the inner core or outer ring of the pots. There were significantly higher levels of larval infection in the center core (56%) of the pot than from media sampled from the outer ring (50%). The percentage of larvae infected with M. anisopliae gradually declined from >90% on week three to 40-60% by week nineteen. The level of larval infection then rebounded over the fall and winter months of 2004 to 75-80% followed again by a slow decline over the course of the 2005 growing season to 30% by the end of the experiment. These data demonstrate that M. anisopliae (F52) has the potential to control infestations of BVW larvae for one or more growing seasons with a single incorporation at planting in containerized nursery production.

Technical 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 US Environmental Protection Agency for BVW control. The objective of this study was to determine the persistence of M. anisopliae, measured as infectivity against BVW larvae, in soilless potting media at six wholesale nursery locations across the Willamette Valley, Oregon. Fungal granules (0.30 and 0.60 kg/m3) were incorporated into media at potting and fungal persistence determined over two growing seasons. Media was sampled from the inner core and outer ring of each pot. Metarhizium anisopliae persisted in the potting media over the duration of the experiment (two growing seasons) with 50-60% of the larvae exposed to fungal inoculated potting media becoming infected. The percentage of larval infection differed significantly between media sampled from the inner core or outer ring of the pots. There were significantly higher levels of larval infection in the center core (56%) of the pot than from media sampled from the outer ring (50%). The percentage of larvae infected with M. anisopliae gradually declined from >90% on week three to 40-60% by week nineteen. The level of larval infection then rebounded over the fall and winter months of 2004 to 75-80% followed again by a slow decline over the course of the growing season to 30% by the end of the experiment. These data demonstrate that M. anisopliae (F52) has the potential to control infestations of BVW larvae for one or more growing seasons with a single incorporation at planting in containerized nursery production.