Multi-year evaluation of seed-applied nematicides for managing Meloidogyne incognita on susceptible and partially resistant soybean cultivars in Arkansas

Seven commercially available seed-applied nematicides were evaluated in a greenhouse pot experiment and in two field experiments using Meloidogyne incognita-susceptible and partially resistant maturity group IV soybean cultivars. Nematicide treatments were abamectin, fluopyram, pydiflumetofen, Bacillus amyloliquefaciens (PTA4838), B. amyloliquefaciens + cis-jasmone, B. flavus (I-1582), and Burkholderia rinojensis (A396). Soybean plants were inoculated with approximately 3,000 M. incognita eggs/pot in the greenhouse experiment. Field experiments were conducted in sites with naturally high infestation levels, averaging 450 nematodes/100 cm3 soil after harvest. In the greenhouse, lower root galling and nematode reproduction were observed with seed-applied fluopyram compared to other nematicides and the non-treated control on a susceptible soybean cultivar. Whereas none of the seed-applied nematicides consistently suppressed root galling or protected grain yield in either the susceptible or partially resistant soybean cultivars in the field experiments. Nematicides provided an average of 0.3% yield protection for susceptible cultivars and had no measurable effect on partially resistant cultivars. In contrast, partially resistant cultivars produced, on average, 50% greater grain yield than the susceptible cultivar. These results demonstrate that seed-applied nematicides provide minimal yield protection under high M. incognita population densities, whereas host plant resistance remains the most effective and reliable management strategy in soybean production.