OSU study: Bees abuzz over type of blue fluorescent light

Researchers at Oregon State University have learned that a specific wavelength range of blue fluorescent light set bees abuzz.

The research is important because bees have a nearly $15 billion dollar impact on the U.S. economy – almost 100 commercial crops would vanish without bees to transfer the pollen grains needed for reproduction.

“The blue fluorescence just triggered a crazy response in the bees, told them they must go to it,” said the study’s corresponding author, Oksana Ostroverkhova. “It’s not just their vision, it’s something behavioral that drives them.”

The findings are a powerful tool for assessing and manipulating bee populations – such as, for example, if a farmer needed to attract large numbers of bees for a couple of weeks to get his or her crop pollinated.

“Blue is broad enough wavelength-wise that we needed to figure out if it mattered to the bees if the light emitted by the sunlight-illuminated trap was more toward the purple end or the green end, and yes, it mattered,” Ostroverkhova said. “What’s also important is now we’ve created traps ourselves using stage lighting filters and fluorescent paint – we’re not just reliant on whatever traps come in a box. We’ve learned how to use commercially available materials to create something that’s very deployable.”

Fluorescent light is what’s seen when a fluorescent substance absorbs ultraviolet rays or some other type of lower-wavelength radiation and then immediately emits it as higher-wavelength visible light – think about a poster whose ink glows when hit by the UV rays of a blacklight.

Like humans, bees have “trichromatic” vision: They have three types of photoreceptors in their eyes.

Both people and bees have blue and green receptors, but the third type for people is red while the third kind for bees is ultraviolet – electromagnetic energy of a lower wavelength that’s just outside the range of human vision.

Flowers’ vibrant colors and patterns – some of them detectable only with UV sight – are a way of helping pollinators like bees find nectar, a sugar-rich fluid produced by plants. Bees get energy from nectar and protein from pollen, and in the process of seeking food they transfer pollen from a flower’s male anther to its female stigma.

Building on her earlier research, Ostroverkhova, a physicist in OSU’s College of Science, set out to determine if green fluorescence, like blue, was attractive to bees. She also wanted to learn whether all wavelengths of blue fluorescence were equally attractive, or if the drawing power tended toward the green or violet edge of the blue range.

In field conditions that provided the opportunity to use wild bees of a variety of species – most bee-vision studies have been done in labs and used captive-reared honeybees – Ostroverkhova designed a collection of bee traps – some non-fluorescent, others fluorescent via sunlight – that her entomology collaborators set up in the field.

Under varying conditions with a diverse set of landscape background colors, blue fluorescent traps proved the most popular by a landslide.

Researchers examined responses to traps designed to selectively stimulate either the blue or the green photoreceptor using sunlight-induced fluorescence with wavelengths of 420 to 480 nanometers and 510 to 540 nanometers, respectively.

They found out that selective excitation of the green photoreceptor type was not attractive, in contrast to that of the blue.

“And when we selectively highlighted the blue photoreceptor type, we learned the bees preferred blue fluorescence in the 430- to 480-nanometer range over that in the 400-420 region,” Ostroverkhova said.

Findings were recently published in the Journal of Comparative Physiology A. The Agricultural Research Foundation and OSU supported this research.

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Here’s a release from the Natural Resources Conservation Service’s Oregon office:

Some scientists estimate that pollinators make possible one out of every three bites we take of our food. While bees are the most important pollinators for crops, butterflies, moths, birds, bats, beetles, wasps and flies all play a vital role in sustaining and advancing agriculture.

National Pollinator Week is June 18 – 24, and it’s a time to get in on the buzz and find out what you can do to protect pollinators.

More than three-fourths of the world’s flowering plants and about 35 percent of the world’s food crops depend on pollinators to reproduce. In the United States, more than 3,500 species of native bees help increase crop yields and ensure that wildlife have abundant access to fruits and seeds.

Despite their pivotal role, many pollinators are at risk. While the alarming decrease in bee and bat numbers has recently made headlines, other species have also declined in the face of habitat loss, disease, parasites, and pesticide exposure.

The good news is, you can help. Habitat restoration starts as close as your backyard.

There are two important habitat requirements for bees: 1) food and 2) shelter, both of which need to be protected from exposure to insecticides.

Food. Bees eat pollen and nectar. In the process of gathering these resources, they move pollen from one flower to another, and thereby pollinate your crops and gardens. Bees rely on an abundance and variety of flowers and need blooming plants throughout the growing season. Plants that are native to the Northwest are particularly valuable for bees, as well as a variety of wildlife and beneficial insects.

Shelter. Oregon native bees don’t build the wax or paper shelters we associate with honey bees or wasps, but they do need places to nest. Wood-nesting bees are solitary, often making individual nests in hollow stems or beetle tunnels in standing dead trees. Ground-nesting bees typically dig nest tunnels underground, especially on warmer south-facing slopes. Bumble bees make use of small cavities, such as abandoned rodent burrows, wherever they can find them.

7 ways to make your garden a haven for native pollinators:

1. Use pollinator-friendly plants in your landscape. Shrubs and trees such as California lilac, Oregon grape, red-flowering currant, cascara, rosemary, blueberry, cherry, plum and willow provide pollen and/or nectar early in spring when food is scarce.

2. Choose a mixture of plants for spring, summer, and fall. Different flower colors, shapes, and sizes will attract a variety of pollinators. If you have limited space, you can plant flowers in containers on a patio, balcony, and even window boxes. Try to have something in bloom during each season.

3. Reduce or eliminate pesticide use in your landscape, and incorporate plants that attract beneficial insects for pest control. If you use pesticides, use them sparingly and responsibly.

4. Accept some plant damage on plants meant to provide habitat for butterfly and moth larvae.

5. Provide clean water for pollinators with a shallow dish, bowl, or birdbath with half-submerged stones for perches. This is especially important for managed European honey bees.

6. Leave dead tree trunks, also called “snags,” in your landscape for tunnel-nesting bees. Plant pithy-stemmed shrubs, such as elderberry and raspberries, and leave some dead stems and canes for bees to move into.

7. Support land conservation in your community by helping create and maintain community gardens and green spaces to ensure that pollinators have appropriate habitat.

Improving pollinator habitat on farms

When it comes to farming, native bees are valuable crop pollinators. Hundreds of species of native bees (often called pollen bees) help increase crop yields and may serve as important insurance when managed European honey bees are hard to come by.

There are simple, inexpensive ways farmers can increase the number of native bees living on their land.

1. Know the habitat on your farm. Look for areas on and around your land that can support native bees. Most native bees are solitary or live in small colonies. Mining bees and mason bees are especially important for early spring blooming crops. Bumble, digger, and sweat bees are valuable for late spring and summer blooming crops.

2. Protect flowering plants and nest sites. Once you know where bees are living and foraging, do what you can to protect these resources from disturbance and pesticide exposure.

3. Enhance habitat with flowering plants and additional nest sites. Most bees seek out the sun and prefer to nest in dry places. Nests are created underground, in twigs and under debris, and in dead trees or branches. Seventy percent of bee species build nests in the soil. You can add flowers, leave some ground untilled, and provide bee blocks (tunnels drilled into wood) or bundles of hollow stems to increase the number of native bees on your farm.

4. Protection from pesticides. Most insecticides are deadly to bees, and unnecessary herbicide use can remove many of the flowers that they need for food. If you use insecticides, choose ingredients targeted to specific species (for example, Btk for pests such as leaf rollers) and the least harmful formulations (i.e., granules or solutions). Spray on calm, dry evenings, soon after dark when bees are not active. Keep in mind that even when crops are not in bloom, some pollinators are visiting nearby flowers, where they may be killed by drifting chemicals.

5. Minimize tillage. Many of our best crop pollinators live underground for most of the year, sometimes at the base of the very plants they pollinate. To protect them, turn over soil only where necessary.

6. Allow crops to bolt. If possible, allow leafy crops like lettuce to flower. Consider delaying the termination of blooming cover crops like crimson clover or buckwheat, and delay mowing or raise the height at which you mow field borders, orchard understories, or nearby lawns to allow white clover to bloom. All of these practices give bees additional food sources.

7. Plant hedgerows or pollinator strips: If you want to do more to increase the number of native bees pollinating your crops, you can plant hedgerows or windbreaks with a variety of flowering plants and shrubs. See how this Polk County vineyard is maximizing pollinator habitat on the farm: http://arcg.is/1XHSrb/

Learn more about how you can help native pollinators at www.xerces.org/pollinator-conservation and http://bit.ly/NRCS_pollinators.

Learn more about how Oregon farmers are helping pollinators at http://arcg.is/1XHSrb/.