Botanical Extracts for the Control of Plant-Parasitic Nematodes: Diversity, Modes of Action, Advanced Formulations, and Efficacy

Plant-parasitic nematodes (PPNs) cause substantial yield losses across a wide range of economically important crops worldwide, and the progressive withdrawal of synthetic nematicides due to toxicological and environmental concerns has created an urgent need for safer alternatives. Botanical extracts, owing to their chemically diverse secondary metabolites and multi-target nematicidal activity, represent one of the most thoroughly studied options. The present work synthesizes and critically evaluates the current state of knowledge on botanical extracts as nematicidal agents, encompassing phytochemical diversity, extraction methodology, nematicidal mechanisms, advanced formulation strategies, and the principal constraints limiting field-scale applicability. Research coverage has been markedly uneven: most studies have concentrated on a small set of plant families, particularly Lamiaceae, Asteraceae, Brassicaceae, and Meliaceae, with Meloidogyne spp. as the predominant target, while many other taxa remain underexplored. Proposed nematicidal mechanisms include oxidative stress, cholinergic interference, disrupted intracellular pH regulation, impaired detoxification, and induction of cell death; yet mechanistic integration through multi-omics approaches remains limited. Activity under laboratory conditions often declines markedly in soil, largely due to compound instability or volatility, a limitation that encapsulation and nanoemulsion formulations are beginning to address. Future research should prioritize standardized mechanistic studies and replicated field trials to bridge the gap between laboratory promise and practical nematode management.