Throughout our decades of pesticide use we have tried to create pesticides that are lethal to pests but don’t affect non-target organisms such as ladybirds and bees. One of the avenues scientists are going down for this reason is GM crops. This 2010 study published in Ecotoxicology looks at the effects of Chinese GM cotton on the honeybee.
Bee declines and colony collapse disorder have complex causes, and one of the reasons we struggle to detect some of them is that they’re more subtle than killing the bees; instead they alter their behaviour. Bees feed pollen to their young during an important stage of their development so it is possible that being fed pollen from GM crops affects their ability to learn. Learning is fundamental to a bee’s lifestyle and determines how efficiently they can forage, so a reduced learning ability can influence the colony’s survival.
Laboratory studies on the effects of the GM cotton show it doesn’t kill bees, but does eating the pollen affect bees’ ability to learn?
The answer was no – bees fed GM pollen were are good as bees fed non-GM pollen. Interestingly, they also tested bees fed on plants sprayed with the insecticide imidacloprid. These bees did show a reduced learning ability. So, in this context, the GM crop didn’t have the same negative impact on bees as conventional insecticide.
Working out whether bees are learning is surprisingly easy. The proboscis extension reflex (PER) is a widely used way to measure learning. Bees are taught to associate an odour with a food reward. They very quickly (sometimes after only one go) learn to extend their proboscis when they detect the odour. This study compared what proportion of the bees learnt in this way when fed on the GM crop, non-GM and also the crop treated with insecticide.
Both Emma and I have trained bees like this. If you’d like to read more about how PER works and about other uses for it (in this case explosive detection) then take a look at Anna Khot’s article.
Han P. Et al. (2010) Use of an innovative T-tube maze assay and the proboscis extension response assay to assess sublethal effects of GM products and pesticides on learning capacity of the honey bee Apis mellifera L. Ecotoxicology DOI 10.1007/s10646-010-0546-4
This work ties in very neatly with Emma’s. She is working out whether bees’ learning is affected by disease, and this study is the equivalent for GM pollen.
Honeybees account for at least 80% of the pollinating insects of major crops, so it’s great to see our understanding of how agriculture affects them becoming ever more detailed.