Animal-crop rotation system: A hurdle for the use of the nematophagous fungus Duddingtonia flagrans

Abstract

The fallow period can represent an opportunity to farmers if the field can be trimmed to receive finishing cattle. Nematode control remains important at this stage, and the use of biological agents such as nematophagous fungi is desirable. Nonetheless, the indiscriminate use of fungicides on agricultural crops may affect the development and survival of fungal propagules. Therefore, we evaluated the in vitro activity of 14 agricultural fungicides against the Duddingtonia flagrans strain ARSEF 5701. The assays were based on CLSI M38-A2 broth microdilution and the agar diffusion method. The fungicides azoxystrobin, cyproconazole, cyprodinil and tebuconazole showed minimum inhibitory concentrations for D. flagrans below their respective maximum residue limits. Although complete radial growth inhibition was only observed for carbendazim at the maximum concentration tested, D. flagrans proved to be resistant to only two fungicides, cyprodinil and iprodione. The present study indicates that D. flagrans is sensitive to most of the common agricultural fungicides, and resistance depends upon the structure, i.e., hypha or chlamydospore. On the basis of these in vitro results, we concluded that the use of agricultural fungicides could seriously hamper the survival of the fungus D. flagrans in amended soils.