The findings from an 18-year study have concluded that use of pesticides, known as neonicotinoids, are more likely to lead to a long-term population decline among wild bees that forage on plants treated with the chemicals than those who feed on non-treated flowers, according to an article on reuters,com.

The research focused on 62 species of wild bees across Britain and the data establishes a link between the declining population of the insects and the application of these chemicals, which are used worldwide.  Previous laboratory testing has shown the insecticides to be harmful to certain bee species, most notably commercial honeybees and bumble bees.

Neonicotinoids were initially licensed in Britain back in 2002, and by 2011, some 83 percent of oilseed rape seeds, plants on which many species of wild bees like to forage, were being treated with the chemicals.  The new research attempted to determine how the use of the products had an influence on the numbers of wild bees and what changes had been seen in the population.

The findings showed that the bees feeding on the treated seed plants were three times as likely to experience a decline in population when compared to those foraging on other wild growing plants.  Five of the 62 studied species saw a decline in population of over 20 percent, while the worst was found to have a 30 percent decline.

Prior to the study, people had an idea that something was happening to the bee populations, but the scale of the issue was eye opening, according to Ben Woodcock, co-leader of the study.  He added the results show the decline is “long-term,” and it was having an impact on more species than previously suspected.

Woodcock, who is an ecological entomologist at the Natural Environmental Research Council Center for Ecology and Hydrology, said the average decline across all species was seven percent, but among the 34 species that forage on oilseed rape plants, it was over 10 percent.

The research was based on data from 1994 through 2011, and was published in the journal Nature Communications.