Posts Tagged: pollination
Have you seen the blaze of super blooms popping up alongside orchards and field crops in our rich agricultural Central Valley? The corridors of poppies, tidy tips, yarrow, baby blue eyes, and redbud planted by farmers, dazzle us with color, but they serve a purpose, too.
The flowers provide nectar and pollen for the pollinators, including honey bees, bumble bees and carpenter bees. Look beyond the buzz, and you'll see other beneficial insects, such as lady beetles (ladybugs) and their larvae devouring aphids, and tiny parasitoid wasps preying on stinkbugs and armyworms. They're (unpaid) pest control agents at work.
Farmers are taking notice. Knowing that most beneficial insects rely on floral resources to survive and reproduce, they're bordering their field crops with strips of flowering plants. In addition to gaining pollination and pest control services, they're gaining financial benefits. University of California researchers documented that pest control and pollination benefits will help pay the cost of a 1,000-foot-long-flowering hedge planting within 7 to 16 years. Their research, Pest Control and Pollination Cost-Benefit Analysis of Hedgerow Restoration in a Simplified Agricultural Landscape, was published last year in the Journal of Economic Entomology.
Other benefits of field edge habitat plantings can include weed exclusion, air quality improvement, erosion reduction, wind protection, shade, and wildlife habitat.
What plants are best to attract beneficial insects to farms and gardens? The UC Statewide Integrated Pest Management Program (UC IPM) has just published a list of insectary plants on its website. The list includes native California perennial flowering shrubs and wildflowers suited for field-edge plantings.
UC IPM defines insectary plants as “those grown to attract, feed, and shelter insect parasites (parasitoids) and predators to enhance biological pest control. Insectary plants provide nectar and pollen for adult natural enemies to consume. Even if pests are abundant, certain natural enemies may be less abundant, shorter-lived, or produce fewer offspring unless nectar and pollen resources are available. Insectary plants can also host alternate prey that will feed the natural enemies and keep them abundant locally.”
Are you concerned about rodents and food safety issues from hedgerows plantings? Not to worry. A recent study by UC Agriculture and Natural Resources (UC ANR) researchers found minimal adverse influence on larger agricultural landscapes. A bonus: Migratory songbirds, like goldfinches, often seek out the seeds from the flowering plants in the hedgerows and offer their own display of color. What about weeds? Yes, they can be problematic. Be sure they're well-controlled before planting wildflowers; think soil solarization and herbicides.
Another UC ANR-associated study, Determinants of Field Edge Habitat Restoration on Farms in California's Sacramento Valley, published this year in the Journal of Environmental Management, found that landowners and farmers familiar with the benefits were more likely to adopt these small-scale habitat restoration plantings on their farms. Also important is technical support from agencies such as the USDA, UC Cooperative Extension Service, and the Xerces Society for Invertebrate Conservation, and the sharing of information from farmer-to-farmer and neighbor-to-neighbor.
Something else we can all do: Share your photos of field-edge habitat plantings and your observations on social media. They tell an important story and can inspire landowners to diversify farmlands. This will help drive home the point that providing flowers for beneficial insects, including bees and natural enemies, will build resilience in our farming systems. Natural pollination and pest control services help counter the disastrous effects of colony collapse disorder and other honey bee maladies, and pesticide resistance.
And it's a counter-punch of color.
That old adage takes on more meaning when you plant wildflower strips on your farm. Wildflowers add resilience to our farming systems by providing bees with habitat and food - pollen and nectar. And they're not just for honey bees. Many native bees, such as bumble bees and blue orchard bees, are important crop pollinators. Currently about a third of our crops benefit from bee pollination. This includes vegetables, fruit and nuts, as well as crops grown for seed production, including sunflower, melon, and carrot.
Farmers primarily rely on honey bees for crop pollination; generally two colonies per acre are needed. Honey bees are efficient pollinators, but with colony collapse and increasing colony losses, we must diversify our farming systems so we don't rely solely on honey bees.
Some important native bee crop pollinators include bumble bees, sunflower bees, squash bees, mason bees (blue orchard bees, which pollinate almonds, are mason bees) and leafcutter bees.
The benefits of native bees? Generally they forage on flowers earlier in the day than honey bees do, they tolerate more wind and cooler temperatures and often they're more efficient at gathering and moving pollen from one flower to another. Native bees also prompt honey bees to disperse more, resulting in more pollinator efficiency. All this is important for good pollination and crop production, especially for crops like almonds that bloom in late winter when the weather is more unpredictable.
Many native bees, including squash bees, nest in the soil, generally excavating chambers about 12 inches deep, where they pack cells with pollen for their young. Bumble bees often occupy vacated rodent holes. Leafcutter bees nest in woody cavities, often taking advantage of old beetle galleries. Discing and land clearing removes their nesting sites and potential food sources, but if you add wildflower plantings and hedgerows of flowering shrubs on your farm, that brings them back. Farms with strips of flowers along field edges have higher numbers of native bees than those that do not. Honey bees also benefit from better nutrition from flowers, strengthening their resiliency to pests, diseases, and pesticides.
A recent study, Pest Control and Pollination Cost–Benefit Analysis of Hedgerow Restoration in a Simplified Agricultural Landscape, published by UC Agriculture and Natural Resources (UC ANR) and UC Berkeley, describes the economic value of these plantings. Generally, a $4,000 investment to plant a 1,000-foot hedgerow of native California plants, takes about seven years to pay off from enhanced pest control and pollination services from natural enemies and bees (where honey bees are limiting). If cost-share funding is available from the USDA, this will reduce the investment cost for the restoration and time on returns.
Although habitat plantings are definitely beneficial, some farmers have expressed concern that these plantings will bring in more pests, including rodents, birds and weeds. However, current UC ANR studies show strips of flowers on field edges export beneficial insects into adjacent crops for enhanced pest control. The wildflower strips are too small to support large numbers of rodents or flocking birds that can damage crops (with the possible exception of ground squirrels and cottontail rabbits), and weeds requiring management are present regardless of field edge habitat.
Water? Although it's hot and dry out right now, many wildflowers do not need summer water. This includes Bolander's sunflower (great for songbirds like goldfinches, but the seeds should not be included in row crop mixes as they will cross-pollinate with our hybrid sunflower seeds), milkweed (great for monarch butterflies), vinegarweed, tarweed, gumplant, turkey mullein (doves love these seeds), and summer lupine. Bees, including natives and honey bees, thrive on these hardy flowers, especially now that the growing season is ending, and few crops are blooming.
Look for more information on wildflower and hedgerow plantings on the Hedgerow Hub website, , the Xerces Society website, and UC Davis fact sheet Habitat for bees and beneficials.
Networking is important too. A recent UC ANR survey showed that networking among growers, landowners, and conservation agencies is crucial in the adoption and implementation of new ideas, such as wildflower plantings.
Bottom line: Wildflower strips can ensure a healthy, sustainable food supply for crops that rely on bee pollination. “Bloom where you're planted” equals “Reap what you sow.”
The average American eats 21 pounds of onions per year. Indeed, our appetite for the fresh green as well as yellow, red, and white bulb onions is increasing in the United States, up 70 percent from several decades ago. A valued crop generating $1.2 billion a year, the onion currently ranks No. 2 in the vegetable industry, right behind the potato. Yellow onions account for nearly 90 percent of all onion consumption, followed by red and white varieties.
Onions, cultivated for more than 5,000 years, are one of the most versatile vegetables. They are found in every ethnic cuisine from breakfast to lunch to dinner and are rich in vitamin C and fiber. As Julia Child noted, “It's hard to imagine civilization without onions.”
With a thriving onion industry comes a “crying” need for onion seed planting stock; onions have to flower and set seed. California is a major worldwide supplier of onion seed, with growers producing about 3,000 acres of hybrid onion seed worth about $12 million, and generating an additional $40 million annually in subsequent retail sales. The major growing areas in our state are the Imperial Valley and Colusa County.
Seed companies from around the world contract with growers here in California to produce hybrid onion seed. The many different varieties include red, yellow and white bulbs, including types that are adapted to different day lengths from our northern to southern hemispheres. Growers plant onion bulbs or seedling transplants in late summer with distinct male (male fertile) and female (male sterile) onion lines in the same field. Generally, the field ratio is one row of males for every three female rows and they're tough to tell apart from a distance, but males produce pollen.
In Northern California, flowering occurs for a short four to five weeks the following May and June, with scapes from each bulb producing a white umbel with multiple florets. Growers rely on honey bees for cross pollination, that is moving the pollen from male to female rows. Each acre usually includes 10 to 12 hives. Native bees are also important for pollinating onion flowers, as are flies. No pollinators? No onion seed production.
Thankfully, there are few pests of onion seed, although the recent introduction of the iris yellow spot virus vectored by the onion thrips has resulted in increased insecticide use to control this potentially devastating pest and disease. Recent research by UC Cooperative Extension specialists in Yolo County and UC Davis, however, documented that more than three insecticide sprays applied pre-bloom per year can reduce honey bee visitation to flowers. Insecticides may also interfere with the ability of female flowers to receive pollen; that is, sprays applied near to bloom time can lead to overall lower pollen germination. As a result, growers are now careful to minimize insecticide use in onion seed production fields to ensure good pollination and yields.
Likewise, growers must carefully manage their irrigation water to ensure that the onion flowers produce good nectar rewards to maximize honey bee visitation. Honey bees are attracted to flowers with ample nectar production. Fields that are too wet or too dry show reduced floral nectar rewards and a decrease in honey bee visitation.
After cross-pollination occurs and seeds are set, growers knock down the male rows to remove them to facilitate harvesting of female lines and ensure purity of the seed. Once the female umbels dry down, they are harvested primarily by hand, placed on tarps to fully dry, and then the tiny black seeds from the florets are mechanically threshed with a combine, and cleaned and packaged for retail sales.
Although a small acreage crop in California, onion seed is an important specialty crop that significantly boosts our agricultural economy, as well as providing needed seed for farmers throughout the world.
But, before you can slice them, chop them or dice them, you have to grow them and our California growers do it best.
Additional information on onion seed production can be found at:
fundraiser for undergraduate education, and Allen-Diaz, who has endured bee stings in the past, is willing to take the risk for this important cause. She'll have the help of a noted bee wrangler, UC Davis emeritus professor of entomology Norm Gary. Gary has performed such unlikely stunts as playing the clarinet while covered with honeybees. He will apply a synthetic pheromone to Allen-Diaz's hands to attract the bees, which he says are unlikely to sting unless provoked.
“I'll be holding a precious resource in my hands, one that is essential to life on earth,” says Allen-Diaz. “I'll be placing my hands in Norm's hands to raise awareness about the value of honeybees.”
While raising money for education is certainly a worthy goal, as Allen-Diaz says, the event also draws attention to the plight of our most important agricultural pollinator. In 2006, a number of beekeepers in the Western U.S. noticed their hives had lost 30 to 70 percent of their worker bees. The phenomenon, now known as colony collapse disorder (CCD), is still not fully understood, though a number of factors are believed to be involved. They include habitat loss or degradation and fragmentation, poor nutrition, certain bee management and agricultural practices, natural and chemical toxins, diseases, and parasites. Any one of these factors can affect the insects' ability to combat any of the others. Isolating a single cause, if there is one, has proved elusive.
Many of the fruits and vegetables on the tables of the world are pollinated by insects, particularly bees, and if they were to disappear, our sources of plant food would be restricted to grains and not too much else. It's no wonder CCD is such a concern (for example, see the United Nations Environmental Program 2010 report on Global Bee Colony Disorder and USDA, Honey Bees and Colony Collapse Disorder.
It's not just honeybees, either. Pollinators in general are on the decline worldwide, probably for many of the same reasons that are listed as factors in CCD. They have an essential ecological function on every continent except Antarctica, not merely in service to agriculture. Losey and Vaughn (2006) estimate the value to the U.S. economy of native insects (not honeybees, which are native to Europe) to be at least $57 billion.
As human population grows and becomes more urban, and as habitats get more fragmented, it is no longer adequate to focus conservation efforts merely in non-urban, non-working landscapes.
“We need to figure out how to accommodate as many native species as possible in these kinds of places,” says Patrick Huber of the City of Davis Open Space and Habitat Commission, which has adopted pollinator habitat enhancement as a working goal. The Commission is working to compile a GIS dataset of known big patches of habitat in Davis, in order map pollinator resources around town.
Huber is a geographer in the Landscape Analysis and Systems Research lab at UC Davis, where he focuses on spatial scale in conservation planning. He is working on a tool to help match gardeners with plants that will grow well in their regions, that are locally available, and that provide a network of resources for pollinators throughout the urban landscape and on into the agricultural landscape. For the moment this project is being piloted in Davis, but the hope is to expand it to other communities, tying in resources such as CalFlora.
A recent workshop at UC Davis sponsored by the California Center for Urban Horticulture, Your Sustainable Backyard: Pollinator Gardening, focused on this very issue: what gardeners can do to help pollinators, many of which are bees. (Of 19,500 known bee species in the world, 4,000 can be found in North America and 1,600 in California. There are at least 300 species of bee in Yolo County alone.) Urban gardeners can help pollinators by:
- Planning for succession blooming (in the Central Valley, that means late winter through fall)
- Putting plants in clumps at least 4 feet long if possible (honeybees, especially, like to specialize)
- Putting in plants that provide both nectar and pollen (nectar is fuel for adult bees, pollen is protein for the young)
- Using native plants where possible; they're drought tolerant and have what our native bees need
- Avoiding most-toxic pesticides and herbicides
- Providing a clean source of water (a slow-dripping tap on a sloped surface is ideal; bees like to drink from very shallow sources)
- Providing cavity nest holes in wood for carpenter and other bees
- Leaving some areas of gardens unmulched for ground-nesting bees
There are ways the agricultural landscape can be made more hospitable, too. Neal Williams, professor of entomology at UC Davis, has been working on a project to install 600- to 800-meter plots of flowering plants alongside large fields as resources for pollinators. This has moved out of the trial phase into test plots in coastal and foothill areas as well as in the Central Valley.
Meanwhile, we can all help count our pollinators on May 8, the Day of Science and Service to celebrate 100 years of Cooperative Extension in California. We'll be conducting our own pollinator count here outside the ANR building in Davis: join us, or let us know about yours!
Many thanks to Kathy Keatley Garvey for use of her photos.
The study found that wild bees were more abundant in diversified farming systems. Unlike large-scale monoculture agriculture, which typically relies upon pesticides and synthetic fertilizers, diversified farming systems promote ecological interactions that lead to sustainable, productive agriculture. Such systems are characterized by high levels of crop and vegetative diversity in agricultural fields and across farming landscapes.
“The way we manage our farms and agricultural landscapes is important for ensuring production of pollinated-food crops, which provide about one-third of our calories and far higher proportions of critical micronutrients,” said study senior author Claire Kremen, professor at the University of California, Berkeley’s Department of Environmental Science, Policy and Management. “This result provides strong support for the importance of biologically diversified, organic farming systems in ensuring sustainable food systems.”
Many of the study’s authors, including Kremen, also co-authored a study published March 1 in Science that found that fruit and vegetable production increased when wild pollinators – as opposed to domesticated honeybees – were more abundant.
“That study showed that wild bees helped crop yield, and this study shows that organic crops in a diversified farming system help wild bees,” said Kremen.
Christina Kennedy, senior scientist at The Nature Conservancy, is the study’s lead author.
- Wild Bees Are Good for Crops, But Crops Are Bad For Bees (NPR interview)
- Better Bees: Super Bees and Wild Bees (KQED Quest video)
- Wild bees make honey bees better pollinators (UC Berkeley press release)