The two most widely used pesticides in agriculture, especially on GM crops, are neonicotinoid insecticides and glyphosate-based herbicides. These have become the preferred choice due to their effectiveness as they spread systemically through the plant, and to their low toxicity in mammals.
Inevitably, traces of both are likely to be found together in the same plant where our pollinators will be exposed to them.
Indeed, analyses have shown neonicotinoid and glyphosate contamination not only in the nectar and pollen collected by honey bees but in their honey stores inside the hive. This means all bees, at all stages in their life will be exposed to both toxins.
Although neither pesticide causes instant bee death, increasing concerns are focusing on the possibility of more subtle, long-term and indirect effects on bee behaviour which will ultimately lead to the collapse of the colony .
The behaviour of bees is complex, changing over time as individuals take on different tasks in the hive. Realising how important sensory information is to bee behaviour and that the survival of the hive depends on the ability of individuals to learn the appropriate response to sensory input, a recent experiment examined the effects of chronic exposure to a neonicotinoid, glyphosate and both together on young honey bees' taste perception and scent-based learning ability.
Although there were no interactive effects between the two toxins, both pesticides reduced taste responsiveness and learning.
Interestingly, glyphosate also reduced the bees' food intake. The experiment wasn't designed to explore why: possibly the herbicide made the food impalatable (no alternative food was made available), or possibly the pesticide content made the bees feel unwell. Whatever the reason, poor bee nutrition is bad news for the healthy continuation of the hive.
Sensory-, learning- and feeding-impairment in our most important pollinators are simply not compatible with sustainable food production. Before we actually run out of food, LET'S GET OFF THE PESTICIDE MERRY-GO-ROUND (coming soon, June 2018)
 BEES WITH DEMENTIA - September 2015
- Carolina Mengoni Gaňalons and Walter M. Farina, 2018, Impaired associative learning after chronic exposure to pesticides in young adult honey bees, Journal of Experimental Biology 221
- Young, hive-bound bees befuddled by common chemicals, Cosmos Magazine, 12.04.18
Photo: Creative Commons