|Shrestha, A - UNIVERSITY OF CALIFORNIA|
Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 12, 2009
Publication Date: April 21, 2009
Citation: Hanson, B.D.,S. Schneider,J. Gerik,A. Shrestha, T. Trout, S. Gao. 2009. Comparison of Shank-anf-Drip-Applied Methyl Bromide Alternatives in Perenial Crop Field Nurseries. HortTechnology 19:331-339. Interpretive Summary: Producers of perennial crop nursery stock such as fruit and nut trees and garden roses in California must meet stringent regulations to ensure that the crop is free of economically important nematodes. Currently, these growers depend upon preplant fumigation with methyl bromide to meet this requirement. Because methyl bromide is being phased out due to its deleterious effect on stratospheric ozone, alternative fumigants and application techniques are needed by this industry. The research reported in this paper was conducted to test several currently available alternative fumigants as well as a new active ingredient material in a nut tree and garden rose nursery. Fumigants were applied with both traditional shank injection equipment and through an arrangement of drip irrigation tubing. Several alternative chemicals provided statistically similar control of nematodes, pathogens, and weeds as the methyl bromide treatment, although nematodes were still detected in some plots. In general, nematode control with shank applications were better than the same chemicals applied through drip irrigation and this was particularly apparent at the site with a clay loam soil texture.
Technical Abstract: Methyl bromide has been used extensively at open-field perennial crop nurseries to ensure the production of plants that are free of soilborne pests and pathogens. California regulations require that nursery stock for farm planting be commercially clean with respect to economically important nematodes. Under the terms of the Montreal Protocol, use of methyl bromide by developed countries was phased out January 1, 2005. Although the perennial nursery industry in the United States largely continues to use methyl bromide under Critical Use Exemptions and Quarantine/Preshipment criteria allowed under provisions of the Protocol; nursery growers need viable alternatives to this fumigant. Two fumigation trials in perennial crop field nurseries with sandy loam and a clay loam soils, respectively were conducted to compare efficacy of fumigants applied either through standard shank-injection equipment or as emulsifiable compounds applied through drip irrigation equipment. In the garden rose nursery trial, nematodes were detected at planting in the untreated control, no-tarpaulin 1,3-D + pic, and pic alone several months after treatment. Nematode genera included Meloidogyne spp. (rootknot nematode) and Tylenchorhynchus spp. (stunt nematode). At harvest two years later, rootknot nematode was detected in rose roots from untreated plots and plots treated with untarped 1,3-dichloropropene + chloropicrin, metam sodium, and chloropicrin alone. In the tree nursery field trial, shank-injected treatments typically provided better nematode control than the same chemicals applied via the drip lines although weed control and marketable trees were similar among treatments.