June 18-24 is recognized as National Pollinator Week. Honeybees garner a lot of attention for their role in pollinating so many crops but there are other pollinators at work for vegetable crops, including squash bees. There are 32 economically important crops in Ontario alone that are pollinated by bees and other animals. Honeybees aside, there are about 420 other bee species in Ontario that play their part. A joint research project between the University of Guelph and OMAFRA is studying the squash bee.
Susan Chan, School of Environmental Sciences, University of Guelph, is examining the effects of neonicotinoids on the squash bee as well as whether or not the bee is commonly found on farms. Data collection began in 2016.
“It’s very farmer oriented,” she says of the project. “We’re trying to figure out what the risk areas are and how to evaluate pollen on their crops.” Chan tested on farms across the province, looking for evidence of residue in pollen, soil and nectar. Squash bees are ground-nesting bees and Chan says there hasn’t been any previous research into neonicotinoid residues in soil and if they affect these ground nesters. “That’s what the project is partly doing,” says Chan.
Chan has found that squash bees don’t seem to be at a high risk from exposure to pesticides in nectar and pollen. “Neonicotinoids are often applied to soil and then they’re trans-located into the nectar and pollen of crops. Squash bees only feed on pumpkin and squash. They would be particularly at risk if there were residues in the nectar or pollen of pumpkin and squash. What we found that is in fact there doesn’t seem to be a high risk. That’s really good news.”
Testing was also done for chlorantraniliprole. Chan was surprised; she thought she would find a lot of risk in nectar and pollen but has not found that. “I’m quite relieved that the food source doesn’t seem to be putting them at risk.”
It’s the evidence within the soil that has her concerned. “When we look at (pesticide) presence in the soil we find high risk,” says Chan. She suggests that when the females burrow to dig their nests they come into contact with soil and there is a high risk of exposure to them there. “Not for thiamethoxam in all cases, but for clothianidin somewhat and imidacloprid quite a lot.”
You can’t change the bees’ habitat, but there may be a small solution to start. Chan found strong populations of squash bees that were not nesting in a crop field; those residing on the periphery or in a farmer’s lawn would be safer. “What we can do is start to become aware of these nests and protect them. If a farmer were to find a nest, if they want to preserve squash bees they could designate that place as a non-pesticide area.”
Chan says 70 per cent of bees are ground nesters; her conclusion is that risk isn’t always from nectar and pollen, but sometimes it’s from something else, such as soil. “I think also that it depends on the crop and the usage of the pesticide. If you have a crop that uses fewer neonicotinoids you’ll have a lower risk in the soil. If you apply neonicotinoids as a seed coating and not as a soil drench, your risk is going to be lower. There are so many things to think about but that’s a really good principle.”
Protecting all pollinators is definitely a buzzworthy issue.