Chemical Alternatives to Methyl Bromide for Nematode Control under Vineyard Replant Conditions

Abstract

Vineyard replant disorder is a disease of unknown etiology, currently controlled by methyl bromide fumigation. While not all the components of the disease are known, plant-parasitic nematode densities are often high in vineyard replant soils. Alternatives to the broadly effective general biocide, methyl bromide, are needed for vineyards replanted after January 2005, when import and manufacture of methyl bromide was banned except for exempted quarantine uses and approved critical uses. Two field trials were conducted in vineyards that had been planted to own-rooted Thompson Seedless grapes for 70 to 85 years and were known to support populations of plant-parasitic nematodes. In a randomized block design with five or six replicates per trial, shank-injected and/or drip-applied propargyl bromide (>207 kg ha⁻¹), iodomethane + chloropicrin (50:50, >269 kg ha⁻¹ drip-applied), and 1,3-dichloropropene + chloropicrin (InLine, 468 L ha⁻¹) provided control of plant-parasitic nematodes throughout the first growing season similar to control achieved with methyl bromide (507 kg ha⁻¹). Chloropicrin (448 kg ha⁻¹) provided less nematode control than methyl bromide, but significantly greater control than untreated. An experimental drip formulation of sodium azide (Agrizide, 336 kg ha⁻¹) was insufficient to control nematodes under vineyard replant conditions. Although vine growth in the treated plots was generally greater than in the untreated plots, growth was greater with methyl bromide than with the alternative chemicals. Alternatives to methyl bromide for nematode control in sandy loam soils were documented, but acceptable alternatives for the management of the complex vineyard replant disorder are more elusive.