Controversial insecticides known as neonicotinoids pose a danger to wild bees and managed honey bees, the European Food Safety Authority (EFSA) in Parma, Italy, said in a report released today. Bayer, a maker of so-called neonics, disputed EFSA's findings. But the report is likely to give a boost to those pushing for tighter European regulation of the chemicals.

“This report certainly strengthens the case for further restrictions on neonicotinoid use,” entomologist Dave Goulson of the University of Sussex in Brighton, U.K., said in a statement. The European Commission last year proposed—but has not yet adopted—extending a partial ban on neonics to all field crops.

Neonicotinoids are systemic pesticides. Often, they are used to coat seeds to protect them when they are planted in the ground. After the seed germinates, the pesticide spreads throughout the growing plant and guards it against nibbling insects. But the insecticide is also present in the nectar and pollen, meaning pollinators get dosed, too. Many studies have shown that the chemicals can affect the ability of honey bees to learn and forage, although industry scientists have disputed whether the experiments are realistic enough.

In 2013, the commission banned the use of three neonics—imidacloprid, clothianidin, and thiamethoxam—on flowering field crops such as corn, sunflower, and rapeseed. The pesticides can still be used in greenhouses, winter cereals, and for spraying certain crops after they flower. The ban was based on a review by EFSA.