Alternatives and Improvements to Soil Fumigation with Methyl Bromide

Methyl bromide is the last preplant soil fumigant which, when properly applied, kills roots and soil microbes throughout the surface 5 feet of soil. The current estimate is that 20%to 70%of the applied product is volatilized from the soil surface. Polyethylene tarps slow the volatilization rate but not the overall amount. In 1987 I published an article indicating there would be a 25%reduction in efficiency of tree and vine production if the soil fumigants are lost. Nematode resistant rootstocks are not a replacement for pre-plant treatments but are more accurately a replacement for post-plant nematicides. The current alternative to soil fumigation is 4 years of fallowing, a very expensive option. At this time we have initiated studies on glyphosate, Vapam, and lower rates of methyl bromide for their efficacy against Lovell, Nemaguard, Marianna, and Myrobalan roots. We are field evaluating a portable soil drenching device for delivery of water transported biocides. For growers who use Nemaguard with resistance to all root knot nematodes, we will initiate studies on the use of Sudan grass which increases root knot populations but is detrimental for all other nematodes of trees and vine crops. Application procedures in the study include: a) Use of a dual application of MB totaling 200-250 lb. MB applied at 30-inch depth. b) Use of a portable soil drenching device for delivery of Vapam, Telone, Furfural, Urea, and other biocides. c) Soil pasteurization with steam or super critical water (4,000 psi and 750°F). d) Roundup treatments to foliage prior to removal of orchards and vineyards. e) Flooding. f) Trunk injections prior to tree removal. g) Antagonistic rotation crops especially in concert with treatments listed above.