Mr. Cueff scoffed. “In politics, it’s not the intention, it’s the practice,” he said.

As with elsewhere in rural France, the rolling fields of corn and wheat surrounding this village creep up right to the doorsteps of the residents’ homes — along with whatever chemicals are applied to those crops.

The farmers tending their fields are not supposed to spray pesticides unless the wind blows at less than six miles an hour. But this is Brittany, a peninsula thrust into the Atlantic, where the wind blows in strong from the ocean.

The mayor has spent much of his career trying to put into practice what he calls “the ecology of action, not incantation.” In 2003, he became the first mayor in Brittany to install solar panels on public buildings; the school toilets use recycled rainwater.

On May 18, Mr. Cueff banned the use of pesticides within 450 feet of any dwelling, putting much of the village off limits. Some of the farmers were furious, the powerful farmers’ union was fiercely opposed and its national president, Christiane Lambert, mocked Mr. Cueff on the radio, asking, “Why not cars, too?”