Methyl iodide was evaluated as a soil fumigant as a potential replacem
ent for the widely used soil fumigant methyl bromide. In container tri
als, methyl iodide was significantly more effective than methyl bromid
e against the plant parasitic nematodes Meloidogyne incognita, Heterod
era schachtii and Tylenchulus semipenetrans and the plant pathogenic f
ungus Rhizoctonia solani. In small field plots, soil populations of ro
ot-knot nematodes were no longer detected after methyl iodide fumigati
on at an application rate of 112 kg ha(-1). However, after growing a s
usceptible lima bean host for two months, substantial root-knot gallin
g occurred, while Rhizobium nodulation was absent. At 168 kg ha(-1) of
methyl iodide, root-knot galling was reduced to less than 1%, and no
Pythium propagules were recovered on selective detection media. These
efficacy data support the conclusion that methyl iodide is a likely ca
ndidate for replacing methyl bromide as a soil fumigant. (C) 1998 SCI.