Nematode-trapping fungi in conventionally and organically managed corn-tomato rotations

We tested the hypothesis that nematode-trapping fungi would be more abundant in organically-managed than in conventionally-rnanaged plots (corn-tomato rotation) in the Long Term Research on Agriculture Systems Project (Yolo County, CA). The replicated plots were established in 1992, began receiving different levels of organic matter (Ilo organic amendments or incorporation of a winter legume crop plus composted manure) in 1993, and were sampled for fungi four times, twice near harvest (Sep 1995 and Nov 1996) and twice near planting (May 1996 and 1997). Fungi were quantified using soil dilution and soil sprinkle plates combined with most probable number procedures. The following fungi were detected: ARthrobotrys haptolyla, A. oligospora, A. thaumasia, Dactylella leptospora, Harposporium anguillulae, Meristacrum sp., Monacrosporium eudermatum, Nematoctonus leiosporus, and Stylopage sp. Arthrobotrys thaumasia was the most abundant (about 10 propagules/g of soil) followed by A. oligospora (about 1 propagule/g of soil). Population densities of the other fungi were usually less than 1 propagule/g of soil. Except for N. leisporus, which was detected more frequently in the organic plots, and Me? istacrum sp., which was more abundant in the organic plots, detection frequencies and population densities of nematode-trapping fungi were similar in conventional and organic plots.