Relevance and management of root-knot nematodes in tomato production in Nepal

Abstract

Tomato (<em>Solanum lycopersicum</em> L.) is one of the most economically significant crops worldwide. In Nepal, tomato production is greatly affected by root-knot nematodes (RKN; <em>Meloidogyne</em> spp.). Despite their impact on agricultural productivity, comprehensive information on the distribution and management of RKN species in Nepal remains limited. This study aimed to (i) conduct a socio-agronomic survey and identify RKN species in nine tomato-producing districts of Nepal, and (ii) evaluate sustainable management options incorporating biological control agents (BCAs) and chemical or botanical nematicides. Surveys across nine major tomato-growing districts — Bhaktapur, Chitwan, Dhading, Dolakha, Kaski, Kathmandu, Kavrepalanchok, Lalitpur, and Lamjung — revealed that only 67% of 70 interviewed farmers recognised RKN as a major tomato pathogen. Meanwhile, awareness of its host range was very low (7%). Chemical nematicides were the main control method used, whereas biological and ecological measures, such as marigold intercropping, were rarely employed. Morphological and molecular analyses identified <em>Meloidogyne incognita</em> as the dominant species, followed by <em>M. arenaria</em> and <em>M. javanica</em>. Field experiments at two infested sites (Nala and Jhaukhel) tested the effectiveness of <em>Bacillus subtilis</em> (Serenade^® ASO), <em>Purpureocillium lilacinum</em> (BioAct^® Prime), fluopyram (Velum^® Prime), and Neem-based treatments. There were site-specific differences in effectiveness, with Serenade^® ASO and Velum^® Prime significantly reducing root galling and nematode egg counts, and increasing yield. BioAct^® Prime was more effective in Nala, while Neem and combination treatments showed limited nematode suppression.<br /> Furthermore, greenhouse experiments with the tomato cultivars 'Srijana' and 'Moneymaker' revealed that the efficacy of BCA is genotype-dependent, with trade-offs between nematode suppression and growth promotion. Overall, our research found <em>M. incognita</em> as the predominant RKN species affecting tomato in Nepal and showed the potential of integrating biological control agents with selective chemical and botanical treatments within site- and cultivar-specific frameworks. Strengthening farmer education, resistance screening, and molecular surveillance are critical steps toward sustainable nematode management and resilient tomato production systems in Nepal.