The Blueberries and the Bees

Originally published in the July 2018 issue of the American Bee Journal, and in the Fall 2018 issue of Bee Scene. Permission was granted by the American Bee Journal to republish this article on the Michael Smith Laboratories website. This article reflects the field work completed by the Foster Lab in collaboration with Agriculture and Agri-Food Canada to better understand the causes of bee disease and the possible effects of blueberry pollination.

Written by Alison McAfee from the Foster Lab, Michael Smith Laboratories

 

Thousands of honey bee colonies arrive in the Fraser Valley’s blueberry fields every spring, but beekeepers are worried this crop may be harming their bees.

My alarm only managed to announce one jolting ring before I slapped it off. The clock read 3:45 am, and there was no time to waste. Bleary-eyed, I threw together a thermos of coffee for the road and grabbed the day bag I had packed the night before, complete with sunglasses, 2 bottles of water, granola bars, and a pillow for the long car ride ahead. My colleague, Bradford Vinson, arrived to pick me up at 4:00 am on the dot. I jumped in his pick-up truck and we headed out to the Valley.

Bradford and I were bound for the blueberry fields in Agassiz, a small town in the Fraser Valley of British Columbia, two hours east of Vancouver. There, forty honey bee colonies were waiting for us – all New Zealand packages established earlier in the year – which had just been placed in the blueberry plots to fulfill pollination contracts.

Blueberries are Canada’s biggest fruit export, generating about $400 million in revenue annually. Most of those berries are grown in BC and rely on honey bee pollination for reliable fruit set. But over the last few years, beekeepers have voiced growing concerns over the health of their blueberry-pollinating colonies; in particular, an unusually high incidence of European foulbrood (EFB) disease and a yet-unidentified “snotbrood disease,” which looks similar to EFB but comes back as negative in diagnostic lab tests. Some beekeepers have even indicated that they will decline to participate in blueberry pollination in the future at a scale that could create a major pollination deficit. Too many commercial beekeepers have reported similar concerns to ignore, and it’s time for the issue to be investigated with scientific rigor. We are even willing to get up at 3:45 am to do it.

Heather Higo and Marta Guarna, the project managers, met us in the field to help with the long day of work ahead. We were about to interrogate these colonies for the five most prominent indicators of colony health we could think of: pollen quality, honey quality, amount of brood, presence of diseases, and the size of the adult population. The previous day, we had sampled and measured the same things in forty colonies which were established from the same package source but spared of any agricultural pollination duties. As more Fraser Valley beekeepers got the call to move their colonies into the fast-approaching blueberry bloom, we evaluated a further 120 hives with various genetic origins at four other field sites, creating one of the biggest experiments on bee health in blueberries to ever be conducted.

This isn’t the first time that beekeepers have questioned the impact that blueberry pollination has on their colonies. In the 1980s, Gordon Wardell devoted an entire PhD thesis to the topic of European foulbrood’s association with blueberry pollination in Michigan.¹ He found that there might be a link between the acidity of the pollen and EFB susceptibility; that is, larvae on a diet of less acidic pollens (like blueberry and cranberry, pH 6.0-6.4) were more susceptible to the disease than larvae on a diet with more acidic pollens (like alfalfa, pH 4.4). Interestingly, he found that the same trend held true for more acidic and less acidic pollen patty supplements. In his thesis, Wardell proposed that the mechanism could be rooted in the diet’s ability to change the acidity of the larva’s gut, once ingested.

The logic is that Melissococcus plutonius – the causative bacterial agent of EFB – thrives in less acidic conditions, so the less acidic diet may be having a Goldilocks effect. It’s making the larval gut environment perfect for M. plutonius to multiply. Likewise, the more acidic diet was making the gut less appealing, offering a protective effect. Based on these findings, Wardell developed a nutritional supplement – MegaBee pollen patties – with a carefully adjusted pH to help counteract the low acidity of blueberry pollen. It’s still on the US market today.

Wardell’s experiments were easily the most detailed investigation into the link between EFB and blueberries, but they weren’t the last. Dean Polk, a county agent at the New Jersey Agricultural Experimental Station, reported that similar blueberry-associated EFB and “snotbrood” concerns are being raised by beekeepers on the East Coast of the US. Polk raised this point at the Entomology Society of America conference in Denver, Colorado last November and had conducted a small-scale field experiment to investigate the issue.²

In Polk’s study, the researchers monitored brood area and pesticide residues in commercial hives for the blueberry and cranberry pollination rounds in 2015, ’16, and ‘17. They found that the colonies’ brood areas decreased during the pollination period; however, their ability to draw further conclusions was limited, partially because relatively few colonies were sampled and partially because there were no comparisons to colonies from the same source, but which didn’t participate in blueberry or cranberry pollination. And that is a very important comparison to make, because otherwise skeptics can (reasonably) argue that any decline in colony health could be simply due to other environmental factors like a long bout of bad weather or an outbreak of EFB across all colonies – not just those in blueberries.

So, while concerns over bee health in blueberries have been voiced before, this is the first time it has been investigated at such a large scale. So far, whether there is a significant difference in disease incidence between blueberry pollinating and non-pollinating colonies is unknown. That’s what we hope to find out, and if so, what we can do about it. To get a head-start on addressing the latter, we are not only measuring the health of colonies in and out of blueberries, we are also testing if Wardell’s MegaBee pollen patties can improve colony outcomes in a large-scale, industrial setting, whether the blueberry-pollinating colonies are more EFB-afflicted or not. After all, pH might not be the only benefit of using a pollen supplement.

Blueberries are a notoriously difficult forage source for honey bees. The opening of the bell-shaped flower is usually too narrow for honey bees to efficiently access the anthers (the part of the flower that produces pollen). Kyle Bobiwash, a researcher at Simon Fraser University, published a paper in the Journal of Economic Entomology last year showing that when three species of managed pollinators (Apis mellifera, Bombus huntii, and B. vosnesenskii) were placed in blueberry fields, honey bees brought in the least amount of blueberry pollen per load.³

B. huntii was the clear winner in terms of collection efficiency, bringing in an average of 3 times more blueberry pollen grains per load than honey bees. This is at least in part because some Bombus species are able to utilize “buzz” pollination, in which they grab onto a blueberry bell and vibrate their wing muscles to help release the pollen grains, without having to rub against the anthers.

If honey bee colonies retrieve relatively little pollen from blueberries despite being located in a sea of bushes, then the relationship between blueberry pollen pH, the larval gut environment, and M. plutonius’s preferences may not be as straightforward as it seems. Bobiwash’s study showed that blueberry-pollinating honey bees were only bringing in about 15% blueberry pollen, relative to all the other pollen sources. It could be that it still causes enough of a pH difference to increase susceptibility to EFB disease, especially considering that many blueberry-pollinating colonies move to cranberries next, which are another high-pH pollen source. However, it could also simply be that the honey bees become generally pollen-deficient during their time in the highbush fields, since they (presumably) need to travel farther than normal to escape the blueberry desert and forage on better pollen sources.

Even though honey bees bring in a lower per-capita load of blueberry pollen, honey bees are still effective blueberry pollinators. George Hoffman, from Oregon State University, presented his work at the same Entomology meeting as Polk4 with a talk titled: “Whoops, I stepped in it: A novel mechanism of honey bee (Apis mellifera) pollination of blueberries.” The title speaks for itself. In the talk, he described how honey bees often get pollen on their tarsi (feet) and forelegs while foraging on blueberries, which is enough to pollinate the flowers. Think of it like taking a pinch of pollen from flower to flower, whilst hardly putting any in your pockets.

MegaBee pollen supplements could have the benefit of not only protecting larvae against EFB, but also making up for what could be relatively sparse foraging in the acres of blueberries. Of our 200 project colonies, 120 of them are for the sole purpose of determining if the patty supplementation is beneficial. By May 8th we completed assessing all the project colonies as they were rushed into blueberries, and in about four weeks we will assess them again, right before they move back out. In between, any leftover patties will be carefully removed, weighed, and replaced with fresh ones.

We hope that our 200-colony study will help land concrete answers about what’s going on with the blueberries and the bees. We expect to have preliminary data analyzed by the end of the summer, but some aspects (like the agrochemical analysis of honey and pollen) could take much longer. We are particularly interested in those results, though, because many people – beekeepers and researchers alike – have suggested that fungicides might be the underlying issue. It’s a viable hypothesis, since honey bees do pick up fungicide residues while foraging on blueberry flowers, whether they retain the pollen or not; more and more fungicides (and their adjuvants) have been shown to be less benign than once thought.^5,6

However, we need to remember not to blame the growers for spraying – they have legitimate needs for fungicides and other pesticides. For example, cool, wet springs (like we had in BC over the last couple of years) can jump-start anthracnose, which is a serious fungal fruit-rot disease. It’s one of the most common blueberry diseases in both Canada and the US. But the berries don’t show symptoms until it’s too late – during or after harvest – when nothing can be done to save the crop. Growers can regularly prune and avoid overhead irrigation, but the best way to prevent the disease is to apply prophylactic fungicides. Growers do what they need to do, and in my experience, it’s not because they don’t care about the bees. They are simply looking out for their livelihood. In fact, growers involved in our project are happy to provide us with information on the timing, type, and quantity of agrochemical applications, which will help us interpret our results.

All these factors – fungicide exposure, pollen pH that’s too high, and anecdotes of serious increases of EFB and “snotbrood” incidence – are enough to make beekeepers (understandably) question putting their colonies in blueberries again. Julia Common, one of the cofounders of Hives for Humanity who I wrote about previously,⁷ is one such beekeeper. On top of her and her daughter’s work creating and maintaining therapeutic apiaries in Vancouver’s poverty-stricken Downtown Eastside, she also normally contracts colonies out for blueberry pollination. However, her colonies suffered so badly from EFB and “snotbrood” last year that she didn’t want to send them back to blueberries. “It’s hugely upsetting to see your bees dying,” Julia said to a StarMetro reporter last April.⁸

In the same interview, she said that she considered “walking away from agriculture.” However, Julia has teamed up with our study and agreed to place 50 of her colonies in blueberry pollination to help strengthen our experiment. “I began thinking I actually owe it to the bees to stay in agriculture and figure out if there’s some way to try and see if we can mitigate all these negative factors that the bees are facing.” And if Julia is willing to send 50 colonies to the front line, I’m certainly willing to get up two hours before dawn and work them.

References:
1. Wardell GI. (1982). European foulbrood: Association with Michigan blueberry pollination, and control. Michigan State University.
PhD dissertation.
2. Polk D and Schuler T. (2017). Measures of honey bee health (Apis mellifera) during blueberry and cranberry pollination in New Jersey. Entomological Society of America annual meeting. Conference abstract.
3. Bobiwash K, Uriel Y, and Elle E. (2017). Pollen foraging differences among three managed pollinators in the highbush blueberry (Vaccinium corymbosum). Journal of economic entomology. 111(1): 26-32.
4. Hoffman GD, Lande C, and Rao S. (2017). Whoops, I stepped in it: A novel mechanism of honey bee (Apis mellifera) pollination of blueberries. Entomological Society of America annual meeting. Conference abstract.
5. Fine JD, Cox-Foster DL and Mullin CA. (2017). An inert pesticide adjuvant synergizes viral pathogenicity and mortality in honey bee larvae. Scientific reports. doi:10.1038/srep40499.
6. Mullin, C. A, Fine, J. D., Reynolds R. D. and Frazier, M. T. (2016). Toxicological risks of agrochemical spray adjuvants: Organosilicone surfactants may not be safe. Frontiers in public health. doi: 10.3389/fpubh.2016.00092.
7. McAfee A. (2017). Hives for humanity: Using bees to create social change in the Downtown Eastside. American Bee Journal. 157(9).
8. Cruickshank A. (2018). B.C. beekeepers worry blueberries are making their bees sick. StarMetro Vancouver. [web] https:// www.thestar.com/vancouver/2018/04/28/bc-beekeepers-worry-blueberries-are-making-their-bees-sick.html.

Alison McAfee began researching honey bees in 2013 as a biochemistry undergraduate student at the University of British Columbia, where she is currently pursuing a PhD. She became enchanted with the little ladies and is pursuing a degree in genome sciences and technology, specializing in hygienic behavior and its underlying mechanisms. In 2017, she received the Canadian Association of Professional Apiculturists Student Merit Award – a recognition that honors outstanding achievements in honey bee research and extension. Email her: alison.mcafee@alumni.ubc.ca and check out her blog: www.alisonmcafeeblogs.wordpress.com