Native bees are great pollinators on their own- they have been shown to be more efficient (on a per bee basis) for a variety of crops globally (there is a wonderful paper in the journal Science by L. Garibaldi et al. describing this). Studies are also showing that native bees help make honey bees better pollinators.
The first to examine this phenomena was a paper from my PI Claire Kremen and her former graduate student Sara Greenleaf. They found that behavioral interactions between native bees and honey bees in sunflower increased honey bee efficiency by 6 times. This was because of two major reasons. Typically multiple honey bees will forage on a single sunflower. They can bump into one another and still stay there working their way around the blooms on a head. However, when a native bee and honey bee meet on while pollinating sunflower, they both flew to a new sunflower. This helps move more pollen between different sunflower individuals, which is required for cross-pollination. The second way honey bees increase between flower movement is when they are scared by male native bees who accidentally try to mate with them while zipping up and down rows looking for females of their own species (Greenleaf and Kremen, 2006, PNAS).
A more recent study has found a similar interaction between native bees and honey bees in almond, the most economically important crop in California. Native bees spur honey bees to move between rows of the orchard crop- increasing the amount of pollen from different trees honey bees carry on their bodies. When the honey bees later deposit this pollen on the stigmas, having more pollen from different individuals increases the chances of pollen tube formation (a grain of pollen extending down and fertilizing the ovary- which results in fruit set). Brittain et al. (the authors of this 2013 study published in Proc. R. B) found that this increased fruit set, which translated into more almonds in farms with higher numbers of native bees present. The mechanism causing honey bees to move more in almonds is still unknown- the authors suggest it could be because native bees deplete pollen at flowers (they tend to forage at earlier times of day than honey bees), forcing them to move larger distances, or they could be leaving scent traces on flowers that honey bees avoid. Nevertheless, the positive outcome for farmers remains
These studies makes me wonder if these indirect interactions are going on in every crop, even those that haven’t yet been studied. It seems like our hard-working native bees are doing their part to help honey bees and, in turn, boost yields. Thanks team native bee!
If you are considering adding wildflowers to your hedgerow (or even your parking strip) new work out of UC Davis suggests that you might not need to add as many seeds as you think to achieve lots of blooms that benefit wild pollinators. Exciting news because it means you can save money while still attracting bees!
The research team planted 3 different densities of a mix of native forbs (herbaceous, annual or perennial plants). They found that the ratio of different plant species to one another had the strongest effects, with one species, gumplant Grindelia camporum, dominating the mixes. Gumplant blooms in the late summer, when most other plants have senesced, making the blooms they provide highly valuable to late season pollinators. For a big early season bloom, the researchers found that chick lupine Lupinus densiflorus provided the highest coverage in their study plots.
Here is a list of the different plant species they used if you want to experiment, but adding more species might increase the overall cost of your planting. Be sure to mix-and-match different bloom periods and life-cycles.
For more detailed information, check out their article from the journal Restoration Ecology:
Wilkerson et al. 2014. Diminishing returns from higher density resotration seedings suggests trade-offs in pollinator seed mixes.
Melittologist Lawrence Packer
was interviewed by Terry Gross on Wednesday’s Fresh Air.
He wrote a new book that highlights that conserving diversity in nature and agriculture is key to keeping bees healthy.
Packer‘s new book is called Keeping the Bees: Why All Bees Are at Risk and What We Can Do To Save Them. Read a brief book review and an excerpt.
Then on Science Friday, Dennis vanEngelsdorp , who has been a pioneer in promoting and studying honey bee health, spoke about new research that shows the threats of neonicotinoid pesticides to insectivorous birds. Previous work has shown that neonics are highly toxic to invertebrates, but this is the first study I am aware of that connects the pesticide to harm in vertebrates.
A week ago I gave a talk all about my research on native bee nesting in agricultural landscapes at East Bay Nerd Nite- it was called “the dirt on bees.” You can watch the raw, uncut video in all it’s glory and learn about where bees are nesting and what it might mean for our food security. It’s is available on the Nerd Nite website, my talk starts at 1 hour, 13 minutes, so be sure to cue it up or there is a lot of dead time:
Over the weekend the white house issued a presidential memorandum that calls attention to the continuing decline of honey bee and native pollinators and set a new agenda to begin addressing the issues head-on. First the memorandum establishes a task forces comprised of numerous governmental departments and organizations. It then goes on to highlight the objectives of the task force, specifically to 1. create a pollinator research action plan, 2. generate a public education plan, and 3. build public-private partnerships to increase and encourage pollinator-friendly habitat.
Buried within the memorandum is a directive for the EPA to assess the effects pesticides, including neonicotinoids, on bees. Another interesting focus is for member agencies to re-evaluate permit and management of power line right-of-ways, areas that could be managed for pollinator habitat. The Department of Agriculture has been given 90 days to come up with best practices to enhance pollinator habitat on federal lands- something it would be very neat to be involved in (so we could help them focus on nesting habitat).
At the same time, the USDA has pledged $8 million to agricultural conservation reserve programs in the midwest states to establish new habitat for honey bees (habitats which also benefit native bees).
In all, Pollinator Week was a resounding success in terms of actions taken on capital hill. This is the largest national effort at pollinator conservation since the Pollinator Habitat Conservation Act in the 2008 Farmbill. I look forward to the exciting research and conservation efforts spurred by this timely and important legislation.
Great article on the threats to bees in the East Bay Express, including explanations about the risks of relying on the honey bee from Professor Claire Kremen. Plus, informaiton about why seeds treated with neonicotinoids are so deadly to bees, yet so hard to avoid.
Next week is Pollinator Week!
You can start it off Monday June 16th by going to or live streaming a discussion about bees and their decline, co-sponsored by the Berkeley Food Institute and the Pesticide Action Network:
What’s the buzz about?: A conversation about bee declines, impacts on our food system and what you can do about it