The effect of dazomet and fosetyl-Aluminium on indigenous and introduced arbuscular mycorrhizal fungi in commercial strawberry production

Field and outdoor pot trials were conducted to assess the compatibility of an introduced arbuscular mycorrhizal fungal (AMF) isolate Glomus fistulosum ([Skou and Jakobsen sp. nov.] BEG 31) and indigenous AMF isolate/s, with biocides frequently used in commercial strawberry production, namely dazomet and fosetyl-Al (fosetyl aluminium). In the field trial, ‘Elsanta’ plants did not exhibit any mycorrhizal colonisation by indigenous AMF spp. after soil fumigation with dazomet. Recolonisation by indigenous AMF was low one year after soil fumigation and was possibly as a result of viable indigenous AMF propagules being washed in from adjacent non-fumigated fields. The degree of colonisation by the introduced AMF isolate G. fistulosum decreased by approximately 1/2 of its original value after one year in the field. Despite fosetyl-Al application Phytophthora fragariae Hickman infection was still prevalent in ‘Elsanta’ during the trial. Although fosetyl-Al did not significantly affect mycorrhizal colonisation, % total G. fistulosum root length colonisation and the proportion of it that was arbuscular, significantly decreased with increased sampling time. In the pot trial, foliar applications of fosetyl-Al significantly reduced the percentage of AMF colonisation that was vesicular and this was independent of the number of spray applications. Fosetyl-Al did not significantly influence the metabolic activity of G. fistulosum colonisation.