FRESNO, CALIFORNIA — Commercial beekeepers and environmental organizations filed a lawsuit Thursday against federal regulators for not banning the use of two pesticides they say harm honeybees.

In the suit, filed by the Center for Food Safety in the U.S. District Court in San Francisco, the group asks the U.S. Environmental Protection Agency to suspend the use of insecticides clothianidin and thiamethoxam-known as ‘neonicotinoids,’ a class of chemicals that act on the central nervous system of insects.

The chemicals are used to treat corn, cotton and other crops against a variety of pests. Research shows that the chemicals build up over time in the soil, plants and trees. They are used widely in the Midwest, where many bees used for California’s annual almond pollination are located. Each February, more than half of the country’s honeybees-about 1.5 million hives-are trucked to California’s almond orchards, the nation’s biggest pollination event.

Beekeepers and some scientists have for years blamed the pesticides for higher bee die-offs. Bees are exposed to the insecticides via residues in nectar and pollen and in contaminated dust from planting of treated seeds. Critics of neonicotinoids say they are toxic to bees, making them more susceptible to pathogens, and could be a significant […]