Scientist Jonathan Lundgren believes the USDA retaliated against him because of his research on neonicotinoid insecticides and potential effects on bees and butterflies.

Neonicotinoids are among the most widely used pesticides. Some research shows they harm bees and butterflies, but the chemical industry disputes much of the research.

Lundgren, who works at a USDA research facility in Brookings, S.D., filed a federal whistleblower complaint in October.