Phytotoxicity and Efficacy of Nematicide Seed Treatment on Wheat, Rye, Oats, and Ryegrass1

Abstract

AbstractRoot‐pruning nematodes can restrict roots of winter annual forage grasses (seeded in autumn) and prevent utilization of water at greater than normal depths during autumn droughts in the southeastern U.S. The efficacy of seed treatment as an inexpensive method for precise delivery of the nematicide in the seedling root zone was studied in the greenhouse. Seed of ‘Maton’ rye (Secale cereale L.), ‘Coker 68‐15’ wheat (Triticum aestivum L.), ‘Florida 501’ oats (Avena sativa L.), and ‘Gulf’ ryegrass (Lolium multiflorum Lam.) were treated in acetone solutions of oxamyl (methyl N′, N′‐dimethyl‐N {(methylcarbamoyl) oxy}‐1‐thiooxamiimidate), carbofuran (2, 3‐dihydro‐ 2, 2‐dimethyl‐7‐benzofuranyl methylcarbamate) or phenamiphos (ethyl‐3‐methyl‐4‐(methyl thio) phenyl (1‐ methylethyl) phosphoramidate) containing 0, 0.25, 0.50, 1.25, 2.5, or 5.0% (w/v) nematicide. Seeds were planted in sterilized soil or soil naturally infested with lance (Hoplolaimus galeatus (Cobb) Sher.) and stunt (Tylen‐ chorhynchus claytonii Steiner) nematodes. Both oxamyl and carbofuran were relatively non‐toxic to germinating seed while phenamiphos was quite phytotoxic. Relative tolerances of the grass species to nematicide seed treatment were rye>wheat>ryegrass>oats. Seed treatment at 1.25% w/v with all nematicides reduced the soil population of stunt nematodes, although the effect was greatest on wheat and oats. Stunt nematodes on wheat declined 65% or more with treatment concentrations of 1.25% w/v. Oxamyl was most effective in reducing populations of lance nematodes. These results indicate that seed treatment is a promising economical method of applying nematicide to control plant parasitic nematodes.