Annual bee counts in England show that urban gardens support bee populations. The British government is expected to launch their national pollinator strategy this fall. Learn more in this article from the Guardian.
Instead of spraying crops, sometimes seeds are coated with pesticides, usually before the seed is even distributed to farmers. When the seed is planted the plant begins taking up the compound and expressing in throughout it’s tissues (in leaves, pollen and nectar), though much of the active ingredient is actually lost into the soil and finds it’s way into waterways (Goulson 2013). One worry is that then non-target insects using the crop, such as pollinators, may then be exposed the pesticides, with potential harmful effects. So the question is- does this type of seed treatment actually improve crop yields?
For soybeans, the answer is no, according to an EPA report released today. The report assessed grower pesticide use surveys throughout the US between 2009-13, comparing neonicotinoid treated soy (three different active ingredients: imidacloprid, thiamethoxam, and clothianidin) to non-treated soy. They found that the net economic gain of neonic seed treatments was $0 per acre. Additionally, treated seeds cost slightly more than untreated seeds, potentially leading to a net loss.
Given the potential harms of the pesticide to beneficial insects, and the lack of economic benefit, seed pesticide treatments seem like they are not the most effective way to control pest insects and crop damage. Studies of other crops that use neonic coated seeds, such as sunflower, are needed to determine if this method of pest control is something that should be abandoned for alternate methods. Right now it is challenging for growers to obtain untreated seed, because, as mentioned, it is often done by companies distributing the seeds. Altering the seed companies practices to reflect this data will likely benefit them, growers and the non-target insects that might be harmed by treated seeds.
Pollinated foods provide many of the micronutrients that are essential for human health, including vitamin A (important for growth and development), folic acid (aka folate; helps prevent birth defects), and iron (makes it possible for our bodies to transport oxygen in the blood). However, due to pollinator declines coupled with agricultural intensification (more conventionally managed commercial monocultures), there may be pollinator deficiencies that target certain areas of the globe more than others. A recent paper in the Proceedings of the Royal Society of Britain mapped the overlap of pollinator deficiencies, pollinator-dependent crops that produce high amounts of vitamin A, iron, and folate, and regions with high micronutrient deficiencies. By doing this they hope to highlight areas where pollinator conservation can be targeted to benefit agricultural yields and curb malnutrition.
They authors found that crops providing vitamin A are about 50% pollinator dependent. Top pollinator-dependent crops that are a source of vitamin A are mango, melon and pumpkin, although this varies by region (e.g. okra in India; guava in Thailand). Non-dependent crops include carrots and sweet potato. Only 12-15% of iron and folic acid providing crops require pollination, though some require pollination for production of seeds, but not of the part humans consume. Key crops include sesame, avocado, and pumpkin. (With halloween approaching, it is good to know pumpkin, which abounds right now, can provide us with many key micronutrients).
Areas that have the highest micronutrient deficiencies coincide with areas that grow pollinator-dependent crops which provide these nutrients. Southeast Asia, India, and central and southern Africa are hotspots for pollinator dependence of foods rich in micronutrients. The authors suggest that these areas be targeted for pollinator conservation in agriculture in order to bolster production of these key crops.
This is a very interesting area of study, which has not yet been explored, but can help set global priorities for production of micronutrient-producing pollinator-dependent foods that can help address food security and malnutrition needs.
Article citation: Chaplin-Kramer, Rebecca, et al. “Global malnutrition overlaps with pollinator-dependent micronutrient production.” Proceedings of the Royal Society B: Biological Sciences 281.1794 (2014): 20141799.
Great little piece in the New York Times about the need to continue incentivizing farming practices that benefit the unsung heros of crop pollination: native bees.
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.
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.