Evaluation of methyl iodide as a soil fumigant for root-knot nematode control in carrot production

Methyl iodide performance as a soil fumigant was compared with methyl bromide for Meloidogyne incognita control in carrot production. Both compounds were applied to tarped beds by hot-gas fumigation in growers' fields near Bakersfield, California. Methyl iodide was applied at 112, 168, 224, and 336 kg ha(-1) and methyl bromide at 112 and 224 kg ha(-1). Other chemical treatments included a non-fumigated control, metam sodium (373 liters ha(-1)), applied through overhead irrigation, and 1,3-dichloropropene (1,3-D; 112 liters ha(-1)) commercially shank applied. Soil was either extracted or bioassayed with tomato plants to determine M. incognita populations prior to application of fumigants, 2 weeks after fumigant application, and at carrot harvest. Carrots were rated for marketability based on size and nematode-induced damage. Methyl bromide, methyl iodide, and 1,3 D were effective at reducing M. incognita populations over the season at all rates tested. In both trials, plants in plots fumigated with either methyl bromide or methyl iodide produced at least 161 and 181% more marketable carrots without nematode damage, respectively, than plants in control plots. Methyl iodide was an effective alternative to methyl bromide for nematode control in carrot production.