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 bromi de for Meloidogyne incognita control in carrot production. Both compounds w ere applied to tarped beds by hot-gas fumigation in growers' fields near Ba kersfield, 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 treat ments included a non-fumigated control, metam sodium (373 liters ha(-1)), a pplied through overhead irrigation, and 1,3-dichloropropene (1,3-D; 112 lit ers ha(-1)) commercially shank applied. Soil was either extracted or bioass ayed with tomato plants to determine M. incognita populations prior to appl ication of fumigants, 2 weeks after fumigant application, and at carrot har vest. Carrots were rated for marketability based on size and nematode-induc ed damage. Methyl bromide, methyl iodide, and 1,3 D were effective at reduc ing M. incognita populations over the season at all rates tested. In both t rials, plants in plots fumigated with either methyl bromide or methyl iodid e produced at least 161 and 181% more marketable carrots without nematode d amage, respectively, than plants in control plots. Methyl iodide was an eff ective alternative to methyl bromide for nematode control in carrot product ion.