When people think of pollinators, they often think of honeybees or cute and fluffy bumblebees. Solitary bees, on the other hand, are highly efficient pollinators but rarely receive the same kind of attention. Solitary bees are generalists, meaning they visit a wide range of flowers, and in many cases have higher pollination efficiency than the classic honey and bumblebees. Over the last few months, I’ve been working to better understand how new biopesticides may affect them.
Biopesticides, particularly those utilising RNA interference (RNAi), a natural gene-silencing mechanism, have been gaining some well-deserved interest. The first RNAi biopesticide, using double-stranded RNA (dsRNA) as an active ingredient, was officially commercialised in January 2024 in the US. Milestones such as these demonstrate that integrated pest management is moving towards the use of more biopesticides as we reduce our reliance on chemicals and seek environmentally friendly alternatives. Biopesticides are potentially preferable over chemical pesticides because they are designed to be targeted towards specific pests based on the genetics of the species. On the contrary, traditional insecticides often have generic targets, such as the nervous system, which are common across insects and other organisms.
As always, when approving plant protection products, the risk of having negative impacts on non-target species should be assessed. As dsRNA acts via very different mechanisms compared to chemical pesticides, there is much we still do not know about what non-target effects may occur, and which species might be most vulnerable. We have chosen to study solitary bees due to their ecological relevance as abundant and efficient pollinators, and due to their underrepresentation in regulatory risk assessments.
That is where my recent work comes in!
Over the last few weeks, I have been finalising the methodology for conducting bioassays on the red mason bee (Osmia bicornis). My work has involved balancing the importance of finding a setup where the bees thrive and feed, while also allowing us to monitor the amount of sugar water being consumed per individual bee, their behaviour, and wellbeing. Optimising the setup involved plenty of trial and error. I tested petals and feeding containers, experimented with syringes, and even tried different UV paints to make sure the bees could easily locate and feed within the setup. After settling on a design described in a paper, I built hundreds of those setups, also known as the “beesocosms” (Figure 1). I have completed one batch of bioassays using an insecticide known to affect bees to validate my methods.
In the coming months, I will run similar assays using dsRNA designed to target an essential gene in Osmia. Given our lovely bees are certainly not pests, this dsRNA is intended for laboratory use only and will not be distributed for any other purpose. Our aim is to establish whether Osmia are susceptible to RNAi at all. If these tests confirm this, the dsRNA could potentially be used as a positive control in future bioassays alongside active ingredients that target real pests. In my tests, apart from looking at bee behaviour and survival, I will also investigate what happens inside the bee: does the dsRNA get stuck or degraded in the gut (a main reason for some organisms not being susceptible to dsRNA), or can it reach the cells where it needs to be to trigger gene silencing?
If mason bees are not susceptible even to a worst-case target, it would be very good news for these pollinators feeding in fields where dsRNA-based products are being used in the future. Although, if they are susceptible to dsRNAs, the next step is to see if they will be affected by other targets based on pest genomes. In theory, an organism’s genome should inform us whether they are sensitive to it or not. However, whether that holds true in practice remains to be seen and is something I will be studying.
Overall, our goal is to help ensure that future biopesticides are not only effective at suppressing pests, but also safer for the pollinators we depend on most.