Sustainable alternatives to 1,3-dichloropropene for controlling root-knot nematodes and fungal pathogens in melon crops in Mediterranean soils: Efficacy and effects on soil quality.

The control of agricultural pests is key to maintain economically viable crops. Increasing environmental awareness, however, is leading to more restrictive European policies regulating the use of certain pesticides due to their impact on human health and the soil system. Given this context, we evaluated the efficacy of three alternatives to the soil fumigant 1,3-dichloropropene (1,3-D), which is currently banned in Europe: two non-fumigant nematicides [oxamyl (OX) and fenamiphos (FEN)] and the soil fumigant dimethyl disulfide (DMDS). We analysed the efficiency of these pesticides against root-knot nematodes and soil fungal pathogens (determined by qPCR) as well as the soil biological quality after treatments application (estimated by enzyme activities). Among treatments, 1,3-D and DMDS significantly reduced nematode populations. FEN was more effective in sandy soil, while OX had no effect in any soil. OX and FEN had no effect on fungal pathogens, whereas DMDS reduced the abundance of Rhizoctonia solani and Fusarium solani at the root level in clay-loam soil. Soil quality decreased after treatment application but then recovered throughout the experiment, indicating the possible dissipation of the pesticides. Our findings support DMDS as a potential sustainable alternative for controlling root-knot nematodes and fungal pathogens due to its effectiveness in both studied soils, although its negative impact on soil biological quality in sandier soils must be taken into account. Main finding of the work. DMDS is a reliable alternative to 1,3-D for controlling agricultural pest but its inhibitory effect on soil enzyme activities varied according to the soil characteristics.

Impact of foliar fungicides on target and non-target soil microbial communities in cucumber crops.

The application of foliar fungicides to horticultural crops has raised public concerns worldwide. In fact, it has been demonstrated that such fungicides have an impact on non-target microorganisms in the rhizosphere. Fluopyram, triadimenol and penthiopyrad are three broad-spectrum fungicides recommended to control foliar diseases. In our experiment, these fungicides were applied to a cucumber crop to mainly control downy mildew caused by Pseudoperonospora cubensis and grey mold caused by Botrytis cinerea. At the same time, we found that these treatments also controlled other fungal pathogens affecting cucumber crops, particularly penthiopyrad, which was more effective. Once the fungicide application period was over, the effect decreased, although fungicide traces remained in the soil. Furthermore, microbial soil community analysis indicated that both fungicide treatments affect fungal communities to a greater extent than bacterial communities.