ScienceInsider

The agricultural strategy known as integrated pest management typically requires the use of a wide variety of chemicals. Over the years, agricultural scientists have fought a cat-and-mouse game with insects and plant pathogens, developing new substances as the pests build up resistance to the older ones. One pesticide group at great risk of being banned in Europe is the azoles, compounds used to control plant diseases such as the septoria leaf blotch that attacks wheat. This condition is the most important wheat crop disease in northwest Europe and is caused by the fungus Mycosphaerella graminicola. The disease does not kill the wheat, but plant tissue dies around the locus of infection, significantly compromising the yield of the crop. Originally, septoria was controlled by several types of fungicides, but then resistance began to emerge. One group of chemicals, dubbed MBCs (methyl benzimidazoles), first became ineffective against the fungus during the 1980s. Next were the strobilurins, introduced in 1996. By 2003, M. graminicola had developed widespread resistance to the pesticide class, making it obsolete. Currently, control of septoria relies solely on the triazole group, introduced in the 1970s, but there is growing evidence that these pesticides, or at least some of them, are also losing their efficacy. With most of the azole group under threat by the new rules, the worry is that the fungal pathogen might develop resistance to the remaining effective triazoles, says Lucas.

Scientists have been voicing their concerns since the 91/414EEC directive review process started in 2002. In April 2008, leading agricultural specialists met for a workshop in Slovenia to analyze the potential impacts of the legislative proposals on resistance management in Europe. The resulting Declaration of Ljubljana concluded that “resistance management requires access to a diversity of chemistries, with different modes of action.” The declaration also argues that the hazard-based criteria the revised regulations were using to ban certain pesticides could “compromise the possibility to combat new pest problems, whether crop related or posing threats to human health."

Since then, the proposed pesticide regulations have continued to evolve—scientists say they aren’t even sure of the exact revisions that will be voted on tomorrow. According to an analysis by the U.K. Pesticide Safety Directorate, the rules drafted in the first reading of the legislation would have outlawed about 85% of pesticides currently in use. But the European Commission and the Agricultural Council have now proposed watered-down regulations for Tuesday's vote. If approved, this second reading could lead to the ban of 14% to 23% of pesticides, the PSD estimates.

That still worries Lucas, who presented a petition on 8 December, on behalf of 72 scientists from 11 countries, to Robert Sturdy, a U.K. member of the European Parliament (MEP) and a member of its Environment committee. “We would be the first to say that we are not encouraging a solely chemical approach to the control of disease,” Lucas says. The ideal scenario for a farmer, he says, “is to plant a crop that is self-resistant to all the pests and pathogens that it encounters.” The problem, he says, is that that’s not feasible now. Politicians are overestimating the industry’s and research community’s ability to quickly come up with substitutes and alternatives to the outlawed substances, Lucas cautions. Sturdy strongly opposes the "compromise package," but at this stage, the new legislation is likely to pass despite growing opposition, says a spokesperson for his office.

For Mark Whalon, director of the Pesticides Alternatives Laboratory at the University of Michigan, Ann Arbor, the issue has implications beyond European boundaries. In an age of globalization, if unwanted pest resistance arises in Europe, the United States is likely to suffer from it, too, at some point, Whalon says. An organic farmer himself, Whalon understands the calls for a greener and safer environment. But as editor of the Arthropod Pesticide Resistant Database, he also takes the issue of pesticide resistance very seriously. He notes that eliminating pesticides primarily based on possible human health concerns could leave farmers with ones that are more dangerous to the ecosystems around crops. “Just because it is safer for humans doesn’t make a pesticide safer for the environment,” he warns.

—Sara Coelho