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New evidence shows that the controversial pesticides known as neonicotinoids, or neonics, could be linked to bee population decline.

A new study, published Tuesday in the journal Nature Communications, looks at wild bee populations relative to the use of neonics on the oilseed rape plant in England over 18 years, from 1994-2011. The researchers found that population extinction rates went up along with the pesticide use on the plants, which are widespread throughout the country.

“The negative effects that have been reported previously do scale up to long-term, large-scale multi-species impacts that are harmful,” Dr. Nick Isaac, a co-author of the report, told the BBC. “Neonicotinoids are harmful, we can be very confident about that and our mean correlation is three times more negative for foragers than for non-foragers.”

Across the 34 species analyzed in the study, there was a 10 percent decline in populations attributable to neonic use, the BBC said. Five of the species dropped off by 20 percent or more, and the most affected group went down by 30 percent. In total, half of the population decline in wild bees could be linked to the pesticides, the researchers said.

“Historically, if you just have oilseed rape, many bees tend to benefit from that because it is this enormous foraging resource all over the countryside,” said lead author Dr. Ben Woodcock. “But this co-relation study suggests that once its treated with neonicotinoids up to 85 percent, then they are starting to be exposed and it’s starting to have these detrimental impacts on them.”