Sustainable approach for soil and substrate disinfestation against soilborne pathogens in nursery

Soil fumigation is a more widespread practice for reducing soilborne pathogen inocula from substrates and soil in nurseries. The effects of dazomet and metam-sodium on the survival of Rhizoctonia solani, Sclerotium rolfsii, Ilyonectria palmarum, I. macrodidyma and four Trichoderma species (T. harzianum, T. atroviride, T. koningii and T. reseei) were evaluated in this study. Five experiments were performed in a commercial nursery in Catania province (Sicily, Italy). The field plots were artificially infested with sclerotia/chlamydospores differentiated on plant tissues of each fungal species. Basamid (dazomet) was applied at 100, 160, 200, 400, and 500 kg ha-1, while Divapan (metam-sodium) was used at rates of 250, 350, 400, 700, and 1000 L ha-1. Both fumigants were applied under virtually impermeable film (VIF) or totally impermeable film (TIF). Fungal survival was evaluated after 21 d from plant tissues extracted from soil after treatments and plated on potato dextrose agar. When Basamid was applied at 200, 400 and 500 kg ha-1, and Divapan at 400, 700 and 1000 L ha-1, no viable inocula were recovered for all pathogenic species, whereas Trichoderma spp. viable propagules were retrieved from the fumigated plots, except for T. reseei (Divapan at 1000 L ha-1). Low rates of Basamid (100 and 160 kg ha-1) and Divapan (250 and 350 L ha-1) under VIF were less effective at reducing pathogen viability, while fumigants applied under TIF killed sclerotia/chlamydospores of each pathogenic species except R. solani (Basamid at 100 kg ha-1). Viable propagules of all Trichoderma species were retrieved from fumigated plots with low rates (except when Divapan was applied at 350 L ha-1 under both films for T. reseei and T. harzianum and under TIF for T. atroviride and T. koningii). This research opens the way to the possibility in rate reduction of both fumigants under low-permeability films for eradicating/reducing inocula of pathogenic species in soil with fewer side effects on beneficial Trichoderma species.