A common pesticide could hinder bumblebees’ ability to pollinate plants, says a new study – and that could be a big problem for both agriculture and the natural ecosystems that depend on the bees for survival.

A paper published Wednesday in the journal Nature tested the effects of a pesticide called thiamethoxam on the ability of bumblebees to pollinate apple trees. The study suggested that, at certain levels, the pesticide can have negative impacts on the bees’ pollination abilities, causing colonies to visit fewer flowers and return with less pollen, and resulting in apples with fewer seeds. These results could indicate poor fruit quality and a risk of decreased agricultural output down the line, fueling the fire in an ongoing debate over how certain pesticides affect the environment and whether their continued use should be permitted in the U.S.

The researchers used three groups of bees in their experiment. They exposed the first two groups to two different “field-realistic” levels of the pesticide, or amounts that are actually used by farmers to protect their crops – 2.4 parts per billion and 10 parts per billion. They didn’t expose the third group to any pesticides at all. Colonies exposed to the 10 parts per billion experienced the strongest effects.

Thiamethoxam belongs to a class of pesticides known as neonicotinoids, which are common in U.S. agriculture. Their use has been widely debated in recent years, as research continues to emerge suggesting that the chemicals may have negative effects on pollinators, including bees – even as critics continue to dispute the findings. In the light of such research, the European Union restricted the use of a handful of neonicotinoid pesticides in recent years, including thiamethoxam. However, its use is still permitted in the U.S.

Developed by Syngenta, thiamethoxam is an active ingredient in several insecticide brands.