"Pesticide risk assessment has not kept pace with new generations of crop protection products, but biologists, veterinarians, and farmers can all work together to understand the bigger picture... with pesticides, ultimately the dose makes the poison. If we can keep doses in a safe range, it’s ok for pesticides and beekeeping to co-exist. We just need to manage the dose.” - PhD Scholar Sarah Wood. Wood's research is helping to pave the way for better understanding and better practices.
Neonicotinoids are arguably the most villainized pesticides for honey bee health. This class of insecticides is heavily relied on by agriculture, and also highly toxic to pollinators, but not necessarily highly toxic at environmental doses. Neonicotinoids target the nervous system of insects, causing paralysis and death in agricultural pests. They can also be used systemically- which means they are taken into the plant tissues, to precisely target only the pests which feed on the plant - this is a great advance in contrast to pesticide applications which could hit any insect in the vicinity as they are applied (usually sprayed).
The neonicotinoid group of pest management chemicals is highly controversial not only in North America, but world-wide, making headlines in the spring of 2018 when three varieties were banned in the EU for outdoor use. In the US, the EPA has been petitioned and sued by several groups to take action against this chemical class, and Canada has enacted restrictions on the use of some varieties. But do we fully understand the effects these chemicals have on honey bees or at what quantities they are safe? The answer is – in short – no. Additionally, crop protection uses these compounds widely, and removing them from use or restricting them has economic repercussions, in addition to potential environmental impacts from the available alternatives.
What does all this mean? In order for policy and practices to change, and do so correctly, we need better evidence of how exactly neonicotinoids affect bees. While many research projects have been completed studying the effects, sufficient solid conclusions remain elusive. If we do find better evidence that these chemicals are harmful to bees, it will be necessary to include agriculture and regulating entities in the conversation, and ideally find a common ground where both bees are protected, and agriculture can continue advancing and thriving.
Recognizing the need for a higher level of understanding in this area utilizing new innovative approaches, in 2016 the Costco Canada - PAm partnership awarded a scholarship to Sarah Wood, a PhD scholar at Western College of Veterinary Medicine at the University of Saskatchewan. Sarah brings a unique veterinary background to honey bee research, and is using the science of histology, along with other methods, to study the effects of three commonly used neonicotinoids; (thiamethoxam, clothianidin, and imidacloprid), in the hopes that this technique can help determine the harm thresholds of these chemicals for honey bee colonies. Her approach is aimed at linking the effects on individual bees to colony health and honey production.
Histology consists of looking at tissues under a microscope. It is a classic technique commonly used for human drug testing in animal models – for instance, we can give a drug in trials to a mouse and then microscopically examine the tissues of the mouse to screen drugs for safety in humans. Wood has been utilizing this “old-school” technology in a new way as she is applying it to honey bees, looking for changes at the tissue level under the microscope. Ultimately, she hopes that this will help to efficiently determine the safety of drugs and pesticides in bees prior to applying the compounds at a larger scale in the environment.
Along with using this technique in her current research, Wood is helping to build an important baseline of “normal” honey bee histology which will give other researchers the tools they need to utilize histology in future pesticide research and safety screening.
Image: Honey bee worker head, frontal section, at day 19 of development, stained with Hematoxylin and Eosin. The compound eye (a) and the mushroom body of the brain (b) with its medial and lateral calyces (c) are indicated. PhD Scholar Sarah Wood is looking at the size of hypopharyngeal glands (indicated by arrows) in nurse bees under the microscope after exposing bees in the lab to combinations of insecticides and fungicides. She aims to understand the effect of the crop protection products on the development of these glands, which are critical to the nutrition of the brood in the colony.
Sarah Wood’s research is already providing us with important information about the effects of neonicotinoids on honey bees. In 2017, she published some of her results, and is continuing her research building from the knowledge she has already gained. You can read her paper "Comparative chronic toxicity of three neonicotinoids on New Zealand packaged honey bees" here.
The results of this study show clearly that chronic exposure to high levels of common neonicotinoids decreased honey production, while chronic exposure to medium doses in the environment had no effect on honey production. However, high levels have been documented in pollen and nectar in Saskatchewan, an intensive agricultural area where canola is now the largest crop in production. Even when canola is not actively blooming, neonicotinoids from the crops can contaminate other blooming plants in proximity, lengthening the window of exposure. Additionally, this research shows that weak colonies are more vulnerable to pesticide exposure affecting honey bee performance.
Over the past winter, Wood conducted an overwintering toxicity study on the effects of neonicotinoids in bees. The timing of this study reinforced the need for answers – it was a tough winter in Canada, with colony losses at 32.6%.
Beekeepers in Canada have historically struggled with overwinter losses, frequently asking Wood and her colleagues how to improve overwinter survival, and what factors are contributing to colony mortality. In Saskatchewan bees are often overwintered on canola honey where 95% of canola is treated with neonicotinoids, and another study has shown significant levels of neonicotinoids in Saskatchewan honey .
Recognizing the need to provide beekeepers with answers about the potential link between overwinter loss and pesticides inspired Wood to conduct this study. By replicating a situation where bees are given canola honey in their brood chambers, preliminary results of this study show that chronic high doses of neonicotinoids have a negative effect on overwintering, while medium doses have less of a negative effect. While there are many factors that affect overwintering success , these results are an important piece of understanding the interconnected aspects of bee health.
Wood is hoping that her work recognizes the potential for veterinarians to have a say in honey bee research. She would like to leave a legacy of honey bee research which recognizes that involvement of veterinarians in this field can be beneficial.
Wood also hopes that through her research, she is able to enhance the understanding of colony level effects as well as individual level effects of pesticides on bees, making the link between microscopic level analysis and colony health. She says that "Because [bees] are such complex social organisms, it's often tough to tease that out – but if I can correlate the effect between colonies and individuals it could be a big step forward for pesticide risk assessment in the future."
Project Apis m. is proud to support the work of PhD Scholar Sarah Wood. Wood exemplifies bringing new and innovative practices and tools to bee research, while working issues of high industry concern. She is helping bridge the gap between beekeepers and research, and is adding knowledge to the tool boxes of scientists, beekeepers, and farmers alike.
By Sharah Yaddaw,
Project Apis m.