The study looked at how the use of genetically modified (GM) crops had affected farmers' use of agrochemicals over a 13-year period.
Since 2008, GM crops have accounted for more than 80% of maize and soybean planted in the US. The seeds are modified with genes that kill insect predators and allow the seed to tolerate the herbicide glyphosate.
The study found that maize farmers who used the insect-resistant seeds used significantly less insecticide (11%) than farmers who did not use GM maize. The maize farmers also used 1.3% less herbicide over the 13-year period.
However, soybean crops saw a significant increase in herbicide use, with adopters of GM crops using 28% more herbicides than non-adopters.
Professor Frederico Ciliberto, who led the study, attributes this increase to the fact that weeds have developed resistance to glyphosate. Maize farmers had not yet had to address the same level of resistance, partly because they did not adopt GM crops as quickly. However, the study
found evidence that both maize and soybean farmers increased herbicide use during the last five years of the study, indicating that weed resistance is a growing problem for both groups.
'Evidence suggests that weeds are becoming more resistant and farmers are having to use additional chemicals, and more of them', Ciliberto said.
Sustain member GM Freeze is calling for a freeze on the production or import of GM foods, plants, farm crops, feed, seed or farm animals. Find out about their work here.
Sustain: Sustain The alliance for better food and farming advocates food and agriculture policies and practices that enhance the health and welfare of people and animals, improve the working and living environment, enrich society and culture and promote equity.
