Effects of Alternatives to Methyl Bromide on Soil Free-Living Nematode Community Dynamics in a Greenhouse Study

Abstract

The main aim of this study was to determine the effect of possible alternatives to methyl bromide (MB) on soil free-living nematode community dynamics in a greenhouse system. Three alternative technologies were examined: metham sodium (MS), dosage reduction of MB and MS by a virtually impermeable film (VIF) cover, and soil solarization (SS) combined with select biological control agents (BCA) (SS + BCA). Nematode populations were classified into four trophic groups: bacterivores (BF), fungivores (FF), plant-parasites (PP), and omnivore-predators (OP). Bacterivores were the most abundant trophic group, averaging 62.1% of the total number of nematodes. OP were the second most abundant trophic group and fungivores were the least abundant trophic group, averaging 3.5% of the total number of nematodes. All fumigation practices decreased the total number of nematodes, BF, FF, and PP. The impact of MS on the BF and on the total nematode number was found to be effective in comparison to treatments associated with typical MB application. The impact of MB and MS by VIF cover on the total number of nematodes, BF, FF, and PP, was similar to the impact associated with MB and MS. The effect of SS + BCA on the nematode populations was less pronounced than the effect of the other treatments. However, significant differences in soil total nematode abundance between the four trophic groups were observed between sampling periods (p < 0.01). The fungivore/bacterivore ratio (F/B), fungivore/(bacterivore + fungivore) ratio (modified F/B) and trophic diversity (T) were found to reflect the temporal changes that occurred in the nematode community during the study period, but were not sensitive enough to discern differences between the treatments.