Environmental factors clearly affect the health of leafcutter bees and colony development, but more research is needed to determine which factors affect what aspects of the bee’s life cycle, according to an American bee expert.
“The last questions left are always the most difficult to answer,” Theresa Pitts-Singer of Utah State University told alfalfa producers at the Manitoba Forage Seed Association’s annual conference in Winnipeg.
Leafcutter bees have been spared from colony collapse disorder, which has had a devastating impact on many honeybee populations.
“The honeybee is such a different beast, and it’s used very differently,” she pointed out. “It’s completely domestic in its ways.”
The expert added the way honeybees are moved and expected to forage on less-than-ideal crops, like almond blooms, immediately after hibernation also causes them stress.
One environmental factor facing both honeybees and leafcutter bees is pesticides.
“Even pesticides that don’t specifically kill or target bees may be affecting the larva and things you wouldn’t expect,” said Pitts-Singer. “The thing that is similar is the sublethal effects pesticides can have on bees. Pesticides can affect bees of all sorts, natives bees and managed bees as well.”
Bee pollen shows how prevalent pesticides are in the environment, she said. Pesticides can be found in pollen even when bees forage in an area that has never been sprayed.
“The other unknown is when you combine other types of pesticides, like a fungicide and an insecticide,” she said.
Although a bee’s immune system may be able to individually handle both types of pesticide, the combination might be overwhelming.
Pitts-Singer and her team have been following the lives of leafcutting bees from larva to adult, and then following the bees’ children and grandchildren as well. The research includes monitoring temperatures inside bee shelters and individual cells, marking thousands of individual bees, and building many different shelters positioned in many different ways.
Along the way she has made some interesting observations, such as south-facing boards tend to have higher rates of chalkbrood than north-facing ones.
The researcher also noted more male bees emerge in Canada, roughly two or three for every female, compared to more southern bees that see a one-to-one ratio. Pitts-Singer said the effect of temperature and light on bee sex ratios is one of the many things being examined in her work.
Even though Pitts-Singer’s study has not concluded, she said farmers can work to improve the efficiency of their bees by monitoring conditions on their own farms.
“Basically, what the research is telling me is that you have to monitor multiple factors and see how they all merge together,” she said. “Every year is going to be different.”