Field efficacy of nematicides and cotton cultivars to manage Meloidogyne incognita , Rotylenchulus reniformis , and Hoplolaimus columbus in the U.S.

Five nematicide treatments (soil-applied aldicarb or fluopyram, seed-applied Burkholderia rinojensis strain A396 or fluopyram, and no nematicide) and two cotton cultivars (DP 1646 B2XF and DP 2141NR B3XF) were evaluated between 2021 and 2023 in five states with Meloidogyne incognita-infested soils, six states with Rotylenchulus reniformis-infested soils, and one state with Hoplolaimus columbus-infested soils. DP 2141NR B3XF is marketed as resistant to M. incognita and R. reniformis, but susceptible to H. columbus. In contrast, DP 1646 B2XF is susceptible to the three nematodes. Rotylenchulus reniformis experiments were categorized as low or moderate to high nematode infestation level, while M. incognita and H. columbus experiments were categorized as moderate to high infestation. In M. incognita experiments, aldicarb and soil-applied fluopyram reduced mid-season densities, while all nematicides reduced galling across cultivars compared to the non-nematicide treated control (NTC); however, yield was similar among nematicides. In R. reniformis experiments, nematicides did not affect mid-season densities at either infestation level, but greater yield was observed with soil-applied fluopyram at low infestations compared to the NTC. In H. columbus experiments, there was no impact on nematode suppression or cotton yield by nematicides compared to the NTC. For all three nematode species, DP 2141NR B3XF reduced reproduction and/or infection compared to DP 1646 B2XF; however, yield protection by DP 2141NR B3XF was only observed under moderate to high M. incognita and R. reniformis infestations. Overall, cultivar resistance was the most consistent tool to manage nematode density and protect yield under moderate to high M. incognita and R. reniformis pressure across the varying growing conditions of the U.S. Cotton Belt.