Ecology of Metarhizium anisopliae in soilless potting media and the rhizosphere: implications for pest management
Denny J. Bruck, firstname.lastname@example.org, USDA-ARS Horticultural Crops Research Laboratory, 3420 N.W. Orchard Ave, Corvallis, OR
Studies were conducted to determine the persistence and ecology of Metarhizium anisopliae incorporated into peat and bark-based potting media with and without a crab meal amendment in container grown Picea abies ‘Nidiformis’. Rooted cuttings of P. abies were planted into potting media incorporated with M. anisopliae (1 g of formulated product/L; ~ 6 log10 cfu/g dry potting media). The fungal population in the bulk potting media was quantitatively determined using selective media at 14, 21, 28, 35, 49, 63, 77, 91, 105, 119, 143, 175, 203, 231, 258, 287, and 342 d. The fungal population in the rhizosphere soil was quantitatively determined at 203, 231, 258, 287, and 342 d. M. anisopliae colonized the rhizosphere of P. abies and the fungal population in the rhizosphere soil was significantly greater than in the surrounding bulk soil. M. anisopliae persisted in the peat and bark-based potting media at 6.22 and 5.74 log10 cfu 342 d after incorporation, respectively. Bioassays using bark and peat-based potting media inoculated with M. anisopliae at 6 log10 cfu/g dry potting medium resulted in 93.5 and 97.5% infection of last instar black vine weevil (BVW), Otiorhynchus sulcatus F., respectively. Roots of P. abies inoculated with M. anisopliae as a sole source of incolum infected 76% of 2nd-3rd instar BVW. The ability of inoculated roots to serve as a delivery system for M. anisopliae represents a new method for delivering entomopathogens and would greatly reduce application costs.