A balanced omega-3/6 fatty acid diet can reduce the harms of pesticide exposure for honey bee olfactory learning

Among the stressors honey bees are exposed to in agricultural settings, poor diet and pesticide exposure are common and concerning. We tested if a balanced omega-3/6 fatty acid substitute pollen diet could increase the resistance of honey bees to the harms of pesticide exposure. We raised bees on either a substitute pollen diet balanced in omega 3 and 6 fatty acids (1:1 ratio) or imbalanced (1:5) for two weeks before providing them with either 10 nM thiamethoxam (TMX) in 2.0 M sucrose solution or a control. Using a Proboscis Extension Response (PER) learning assay, we classically extend their proboscises to odors associated with punishment, as expected but did learn odors associated with reward. Bees fed an imbalanced diet and TMX had significantly poorer learning in the sixth learning trial and significantly poorer memory when tested 1 h after this final learning trial. However, bees fed the balanced diet were resistant to the effects of TMX and had normal learning in the sixth trial and normal 1 h memory. Bees fed the balanced diet and exposed to TMX had higher survival than bees fed the imbalanced diet and TMX, suggesting that a balanced diet helped bees exposed to TMX. However, the survival data is complex and may suggest hormesis, in which a short, low dose of pesticide can increase insect survival. Our results suggest that a balanced omega-3/6 fatty acid diet can increase the resistance of honey bees to TMX, providing hope for enhancing the resistance of honey bee colonies