Study Shows Pesticide Drift May Harm Pollinators by Exposing Them to Unintended Flowers

Bees need a balanced diet of nectar which offers them carbohydrates in the form of pollen and sugars which provides fat and protein, from a wide variety of plant sources. Different bee species have their own nutritional needs, but no healthy bee diet includes pesticides.

As per the new findings by scientists from Trinity College Dublin and Dublin City University (DCU), pesticides have been found in the nectar and pollen of flowers that were not targeted with the toxins, and this could be an extra, underestimated hazard for pollinators.

According to a press release from Trinity College Dublin, co-lead author of the study Professor Jane Stout of Trinity’s School of Natural Sciences said, “This is the first time that a multi-field survey of pollen and nectar from crops and wild plants has been undertaken in Ireland and is critical to our understanding of pesticide residues in the Irish context.”

The study was published in the journal Science of the Total Environment, “Pesticide mixtures identified in crops and non-target wild plants pollen and nectar.”

Elena Zioga, a doctorate student at Trinity College Dublin, collected and examined hundreds of flowers from Irish agricultural fields for the study.

The researchers examined the pollen and nectar of crop and hedgerow plants that were not the targets of the herbicides fluroxypyr and glyphosate as well as the fungicides azoxystrobin, boscalid, and prothioconazole.

Also, the researchers looked for the neonicotinoid pesticides acetamiprid, imidacloprid, clothianidin, thiacloprid, and thiamethoxam, some of which had not been used recently and were no longer even licensed in Ireland. These pollutants could, however, linger in the environment for a very long time.

The research team identified and recorded various chemical compounds, most of which came from fields where there has not been a recent application of pesticides. The most common combination was residues from azoxystrobin, boscalid, and clothianidin with the latter seeming to remain for several years post-application.

According to the press release, co-lead author professor Blánaid White of the School of Chemical Sciences at DCU said, "The research takes place in the context of Ireland reaching the ambitious European Commission target in the Farm to Fork Strategy of reducing the use and risk of chemical pesticides by 50%."

In Ireland, herbicides, insecticides, and fungicides are the most commonly used categories of pesticides. Crops which frequently lure pollinators, such as rapeseed, are likely to have been treated with pesticides from all these groups.

Zioga said, “Application of several pesticide compounds from different pesticide categories, at multiple time intervals throughout the cropping period, raises the risk of pollinator exposure to pesticide mixtures through pollen and nectar with unknown outcomes in pollinator’s health,”

Some neonicotinoids that were banned by the European Commission in 2018 that are known threats to pollinators still loiter in the environment.

Zioga also said, “We found clothianidin residues in pollen and nectar of both plant species even though it hasn’t been applied for years. The fact that it remains present in pollinators’ food sources for so long is a concern,”

Understanding the effects these mixes have on pollinators and other creatures not targeted by the poisons is essential since the pesticides the scientists identified were more frequently blends of various types of pesticides than single substances.

In a press release, White said, “Our findings can help us to understand which are the more hazardous pesticides in an Irish context, and also assist us in understanding what are the risks associated with the different chemical pesticides are so that we can more effectively minimize the risk associated with them,”

Multiple pesticide exposure is dangerous for bee health and could have negative effects on crop yield, ecosystem function, and human health.

White said, “We don’t know the full effect on pollinators of consuming foods contaminated with multiple pesticides, and most of what is known are compound specific,”

Zioga added that the effects on bee species other than honey bees needed to be studied as well.

Also, he added, “The toxicity of single compounds is mainly being tested on honey bees, while we have scarce toxicity data on other wild bee species like solitary bees and bumble bees,”

Stout said the long-term effects of various compounds on pollinators also needed to be looked into.

In the press release, White stated that in order to comprehend the extent of various compounds’ persistence, "we need to understand how different compounds travel through the environment and the rate at which these compounds degrade."