Evaluating the in vitro efficacy of varied concentrations of abamectin and fluopyram, alongside different durations and temperatures of hot water treatments against Meloidogyne incognita, the southern root-knot nematode

Abstract

Plant germplasm importation into Aotearoa/New Zealand poses a risk of introducing unwanted organisms. Current biosecurity measures for plant nematodes on imported nursery stock are under review. This study aimed to investigate alternative chemicals that could replace fenamiphos, the current border treatment. Abamectin and fluopyram were chosen for assays based on their demonstrated nemoticidal activity and availablity. Hot water submersion was also tested as a non-chemical alternative. Second stage juveniles (J2s) of Meloidogyne incognita were isolated from infected susceptible tomato cultivars (Solanum lycoperisicum). Preliminary experiments tested the field rates of abamectin (0.009 g/L a.i) and fluopyram (0.3 g/L a.i.) on J2s, with resulting mortality rates of 54.6% and 78.6%, respectively. Preliminary hot water experiments for 3 hours at 44°C showed complete mortality of J2s. Further experiments with abamectin (0.009, 0.018, 0.045 and 0.09 g/L a.i.) and fluopyram (0.3, 0.6, 1.5 and 3.0 g/L a.i.) showed that the highest mortality rate with abamectin was 75.2%. Concentrations of fluopyram ≥ 0.6 g/L resulted in 100% mortality. Hot water treatments for 1 and 2 hours at 44 and 50°C also resulted in 100% mortality. Further experimentation using in planta bioassays are recommended to assess how fluopyram affects nematodes contained within plant tissues. Overall, the study demonstrated the potential of fluopyram and hot water submersion which provided the complete mortality required in biosecurity situations as an alternatives to fenamiphos for biosecurity measures in Aotearoa/New Zealand.