Soil Biotic and Abiotic Responses to Dimethyl Disulfide Spot Drip Fumigation in Established Grape Vines

Abstract

Dimethyl disulfide (DMDS) is a soil fumigant used in agricultural systems as an alternative to methyl bromide (MeBr) for the control of soilborne pests and pathogens. However, fumigants including DMDS that have broad biocidal activity can affect both target and non-target organisms in soil. This study focused on the effects of DMDS on the recovery of ecologically important microbial communities and soil abiotic factors while affecting plant parasitic nematodes in both field and microplot trials. Phospholipid fatty acid (PLFA) analysis was used to characterize changes in microbial community structure over time. Total amount of PLFA as well as all major non-target soil microbial groups such as Gram positive bacteria, Gram negative bacteria, fungi, arbuscular mycorrhizal fungi (AMF), and actinomycetes decreased significantly 15 d after fumigation in the untreated control as well as in all the rates of DMDS tested in a microplot trial. Fumigation had little effect on microbial biomass but at some time points some treatments did affect microbial community structure. Canonical multivariate analysis of variance indicated that soil microbial communities 45, 60, and 90 d after fumigation were similar to one another compared with 15 d after fumigation. The research showed that reduction and changes in microbial community biomass and structure were mainly due to environmental factors and therefore, it is concluded that DMDS fumigation did not impact the activity of beneficial microorganisms. Total N, C, and other abiotic factors were also not affected by DMDS fumigation. Plant parasitic nematodes were greatly affected by DMDS fumigation and this interaction could be related to its mode of action which affects nematode mitochondrial activity.