US researchers are urging government officials to fund large-scale "landscape-level" studies to test the efficacy of pesticide resistance strategies.
US researchers are urging government officials to fund large-scale "landscape-level" studies to test the efficacy of pesticide resistance strategies. They warn that weed and insect resistance to agrochemicals is costing US agriculture some $10 billion a year.
The study, published on May 18th in the journal Science, calls for research across areas of at least 1,000 acres (400 ha) to assess how particular strategies compare to large "control" areas. The authors contend that such landscape studies have become more feasible because of new genomic and technological innovations that could be used to compare the efficacy of strategies for preventing weed and insect resistance. The researchers say that farmers could receive incentives to participate, suggesting that some existing farm subsidies could be shifted to help pay for participation.
"Resistance to pesticides is rising in critical weed and insect species, threatening our ability to harness these pests," says study co-author Fred Gould, an entomologist and agriculture professor at North Carolina State University. "Weed species have evolved resistance to every class of herbicide in use, and more than 550 arthropods have resistance to at least one pesticide."
The study cites problems with glyphosate herbicide, noting that agrochemical companies and farmers have turned to "new" solutions that are actually old, including the herbicides, 2,4-D and dicamba. "We're working down the list of available tools to fight weeds and insect pests," says co-author Zachary Brown, assistant professor of agricultural and resource economics at the University. "It hasn't been economically feasible to develop new herbicides to replace glyphosate, for example, so what's old is becoming new again. But the current incentives don't seem to be right for getting us off this treadmill."
The authors note that the US is about to begin a "huge experiment" with the commercialization of genetically modified crops that are tolerant to dicamba and 2,4-D. The two herbicides will likely be used alone and in combination with glyphosate, "despite a lack of knowledge about what usage pattern would be best for decreasing the emergence of resistance in weed populations while maintaining economic viability," the researchers say. "This ignorance is reflected in the literature from the EPA and the companies that simply tells farmers that diversified approaches to weed management are best for delaying resistance, but with no supporting evidence or incentives."
The recommended landscape-level experiments could test different spray combinations, rotations, or combined cultural and chemical controls on large acreages, according to the authors, and genomic responses of weeds could be monitored carefully to eliminate a failed strategy before resistance evolves.
Such experiments would require large investments and "may seem radical, but governments do make similar investments to decrease erosion, maintain conservation reserve programmes, and subsidize crop-loss insurance", the authors conclude. "Lacking data from bold experiments, we will likely just learn that heavy use of 2,4-D and dicamba results in weed resistance and that we have an even more critical need for herbicides with new modes of action."