Nematicidal Activity of Phytochemicals against the Root-Lesion Nematode Pratylenchus penetrans

Abstract

Plant-parasitic nematodes (PPNs) are highly damaging pests responsible for heavy losses in worldwide productivity in a significant number of important plant crops. Common pest management strategies rely on the use of synthetic chemical nematicides, which have led to serious concerns regarding their impacts on human health and the environment. Plant natural products, or phytochemicals, can provide a good source of agents for sustainable control of PPNs, due to their intrinsic characteristics such as higher biodegradability, generally low toxicity for mammals, and lower bioaccumulation in the environment. In this work, the nematicidal activity of 39 phytochemicals was determined against the root-lesion nematode (RLN) Pratylenchus penetrans using standard direct and indirect contact methodologies. Overall, the RLN was tolerant to the tested phytochemicals at the highest concentration, 2 mg/mL, seldom reaching full mortality. However, high activities were obtained for benzaldehyde, carvacrol, 3-octanol, and thymol, in comparison to other phytochemicals or the synthetic nematicide oxamyl. These phytochemicals were seen to damage nematode internal tissues but not its cuticle shape. Also, the environmental and (eco)toxicological parameters reported for these compounds suggest lower toxicity and higher safety of use than oxamyl. These compounds appear to be good candidates for the development of biopesticides for a more sustainable pest management strategy.

Phytochemical Volatiles as Potential Bionematicides with Safer Ecotoxicological Properties

“…However, the soil composition was reported to impact oxamyl persistence and toxicity [ 61 ], which can lead to inconclusive assessments of potential risks, especially regarding the persistence and toxicity of its degradation residues, e.g., oxamyl oxyme or dimethyl amino oxoacetic acid, which are already quantified in concerning amounts in drinking water [ 62 ]. Thus, oxamyl might be responsible for long-term environmental effects since it was additionally predicted to have a strong persistence in the environment in comparison to volatile phytochemicals [ 45 ]. Fluopyram is a next-generation nematicide that appears to have very strong activity against soil parasitic nematodes without many of the harmful effects of oxamyl.…”

“…They can have strong nematicidal activities (1-dodecanol), lower dispersion in the water environmental compartment alongside lower toxicity to aquatic organisms (3-octanol), and show relatively safe toxicity thresholds for mammals or predicted interference with important organic functions. In previous works with the root-lesion nematode Pratylenchus penetrans , the fatty alcohol 3-octanol was responsible for high nematicidal activities, which is notable given that root-lesion nematodes appear to have strong resistance to volatiles as nematicidal compounds of direct contact activity [ 45 ]. The nematicidal volatiles analysed in this study, which included fatty alcohols such as 1-decanol, 1-undecanol, or 1-dodecanol, were found to have higher nematicidal activities than oxamyl, higher affinity to the air and soil environmental comparts, and overall safer (eco)toxicological parameters.…”