The Effect of Botanicals with Nematicidal Activity on the Structural and Functional Characteristics of the Soil Nematode Community

We investigated the effects of three botanicals with nematicidal properties (anise-Pimpinella anisum, parsley-Petroselinum crispum, and rocket-Eruca sativa) on the soil nematode community, in terms of trophic structure and nematode genera composition. We compared effects with those of fluopyram (synthetic nematicide) and Nemagold (bionematicide). We assessed the role of time, by sampling 15 and 45 days after treatments and analyzing nematode genera and microbial phospholipid fatty acid biomarkers (PLFA). Soil incorporation of botanicals reduced plant parasitic nematodes, increased bacterivores, especially the enrichment opportunists and among them Rhabditis, having no effect on fungivores and non-parasitic plant feeders. Neither the number nor the composition and dominance hierarchy of nematode genera were affected. Nemagold did not induce any significant change, while fluopyram decreased both free-living and parasitic nematodes, but with no uniform effect against all genera. The least affected genus was the fungivorous Aphelenchus. While most microbial PLFAs increased with time, the abundances of nematode genera did not change, except the Meloidogyne incognita second stage juveniles, which emerged in soil only 45 days after treatments. The low enrichment index and high channel index values of the fluopyram soil samples indicated a stressful environment. The opposite was observed in the botanical treatments, especially parsley and rocket.