(Beyond Pesticides, July 31, 2008) The Third International Biofumigation Symposium took place in Australia July 21-25, 2008, highlighting new scientific advancements in the age old practice of planting crops in the brassica family (radish, mustard, etc.) prior to growing other crops to control diseases, insects, and weeds. Research in this area reveals that in many cases, â€śbiofumigation,â€ť as it is called, provides disease and pest control comparable to that of pesticides commonly used as soil fumigants, and does not have the negative health and environmental effects associated with these fumigants.
Growing interest in biofumigation is spurred by the international phase-out of the toxic soil fumigant methyl bromide (for its role in ozone depletion) under the Montreal Protocol. Unfortunately, even though the environmental and health risks of methyl bromide and other soil fumigants have been documented, and non-toxic alternatives such as biofumigation exist, the U.S. Environmental Protection Agency (EPA) has essentially ignored the Montreal Protocol and continued to allow the use of methyl bromide under â€śexemptions.â€ť
In the most recent EPA action on the subject, the agency released proposed rules and risk mitigation measures for five toxic soil fumigants on July 10, 2008. These rules fall short of the hopes of farmworker and environmental advocacy groups because they fail to protect farmworkers, communities, and the environment adequately. The comment period for these proposed rules is open until September 15, 2008.
Biofumigation presents a natural alternative to chemical fumigation and is particularly effective for control of diseases and pests in solanaceous crops such as tomatoes and potatoes. John Kirkegaard, PhD, explains that, “Brassica plants naturally release compounds that suppress pests and pathogens, principally isothiocyanates (ITCs), which most people would recognise as the ‘hot’ flavour in mustard or horseradish. When ITCs are released in soil by green-manuring, soil-borne pests and pathogens can be suppressed and the yields of solanaceous vegetables such as potatoes, tomatoes and eggplants can be increased by up to 40 per cent in some cases.â€ť In addition to brassica plants, other crops have shown biofumigation potential. In one study, incorporation of sorghum was compared to use of methyl bromide in a peach orchard for nematode suppression, and the sorghum performed as a viable alternative to methyl bromide.
In California alone, one of the only states to require pesticide use reporting, over 1.5 million pounds of the five soil fumigants EPA addresses in its proposed rules were used in 2005 (an additional 2.9 million lbs. of methyl bromide was used in strawberry production post-planting). With alternatives such as biofumigation, advocates question the continued use of such toxic chemicals. Ecologically-based farming systems such as organic agriculture and practices such as biofumigation hold the key freeing our agricultural system of its chemical dependency.
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