Efficacy of fumigant and non-fumigant nematicides for Belonolaimus longicaudatus management in potato.

Belonolaimus longicaudatus (sting nematode) is a yield-limiting plant-parasitic nematode in Florida potato production. Fumigation using 1,3-dichloropropene (1,3-D) at 66 kg a.i./ha is a common practice for managing sting nematode, but effective alternatives are needed. Therefore, the objective of this study was to test the efficacy of alternative nematicides and nematicide rates against sting nematode in potato production. A preliminary field trial was conducted in 2022 followed by small plot field trials in 2023 and 2024 in northeast Florida. Treatments in repeated trials included preplant fumigation of 1,3-D at (1) 33, (2), 50, or (3) 66 kg a.i./ha; metam potassium at (4) 125 or (5) 293 kg a.i./ha; (6) a combination of 1,3-D at 33 kg a.i./ha and in-furrow oxamyl; in-furrow (7) oxamyl or (8) fluopyram; and (9) untreated control. Any treatment with fumigation reduced sting nematode population densities relative to untreated control at 6 weeks after planting, and, generally, at harvest. The common practice of 1,3-D at 66 kg a.i./ha remained the most consistent treatment for mitigating damage from sting nematode. 1,3-D at 50 kg a.i./ha or the combination of 1,3-D at 33 kg a.i./ha and oxamyl were consistently better than untreated control, but not as consistent at improving yield as 1,3-D at 66 kg a.i./ha. 1,3-D at 33 kg a.i./ha or metam potassium had inconsistent impacts on yield. Among metam potassium rates, 125 kg a.i./ha had similar efficacy as 293 kg a.i./ha, but was more cost effective. Standalone fluopyram or oxamyl did not improve sting nematode management. In summary, the common practice of 1,3-D at 66 kg a.i./ha was the most consistently effective treatment against sting nematode in potato, but other nematicide treatments also had efficacy.