UTAH PESTS Staff
Utah Plant Pest Diagnostic Lab
Utah Pests News is published quarterly by the UTAH PESTS staff.
The Importance of Native Bees for Farms
Approximately 75% of the world’s flowering plants require animal pollination, including two-thirds of all crops. In 2000, about $20 billion in North American agricultural production was made possible by bee pollination, and roughly $3 billion worth was provided by native (wild) bees.
Many people believe that honey bees can provide all of the pollination services that plants need. However, there are 50% fewer managed hives today than there were in 1950, and those remaining are threatened by pests, diseases, or a combination of factors known as Colony Collapse Disorder. As a result, native bees are becoming increasingly important in agriculture. Unfortunately, according to a recent report by the National Research Council, all pollinators are in decline as a result of habitat loss, deterioration, and fragmentation, in addition to the adverse effects of pesticides.
Native bees supplement pollination provided by honey bees, increasing yields and profit. Pollination is increased not only because the number of pollinators is increased, but also because, in many cases, native bees are more efficient. For instance, when colder, wetter weather prompts honey bees to remain in their hive, mason bees and bumble bees are actively foraging. Also, an individual native bee exhibits more foraging behaviors than a honey bee. For example, honey bees tend to forage for either nectar or pollen. A nectar-foraging honey bee is not likely to contact the anthers of many orchard blossoms, and therefore is unlikely to pick up or transfer much pollen. However, a mason bee, such as a blue orchard bee (Osmia lignaria) (Fig. 1), forages for both pollen and nectar, and is likely to contact the anthers of every orchard blossom it visits. Buzz pollination by bumble bees (Bombus spp.) is another example of increased efficiency due to foraging behavior. Bumble bees vibrate their flight muscles within a flower, causing the anthers to release pollen (Fig. 2). This behavior promotes cross-pollination and increases fruit size and yield in many plants, such as tomatoes and peppers.
Some flowers are shaped in such a way in that they are inefficiently pollinated or avoided by honey bees. Alfalfa is an example of the latter situation, and the alkali bee (Nomia melanderi) is a highly efficient pollinator of this plant (Fig. 3). Some native bee species have evolved as pollinator specialists for certain crops, such as squash bees (Peponapis spp.) for cucurbits.
Some farming operations may benefit monetarily by advertising that they are "pollinator-friendly," which fits with sustainable agriculture practices. Management that promotes native pollinator populations improves farm aesthetics, which can be advantageous for small farms that frequently conduct tours or allow customers to pick their own fruit.
Native bees are valuable to crops. The benefits of native bees can be maximized with a little awareness and some easy modifications of farm management practices. The 2008 Farm Bill contains several programs which provide monetary support for growers that implement conservation plans, including practices that promote native bees. In future articles, I will discuss these programs, as well as what you can do to encourage native bees to thrive on your farm.
-Cory Vorel, USU CAPS Coordinator
Cane, J. and L. Kervin. 2009. Gardening for Native Bees in Utah and Beyond. Utah Pests fact sheet.
James, R. and T. Pitts-Singer, eds. 2008, Bee Pollination in Agricultural Ecosystems; Oxford University Press, New York.
National Resource Council of the National Academies. 2007, Status of Pollinators in North America; National Academies Press, Wash., D.C.
National Resource Council of the National Academies, Status of Pollinators in North America Report in Brief (pdf)
a. 2008 Farm Bill: Benefits to Crop Pollinators.
b. Farming for Pollinators: Native Bees and Your Crops.
c. Farming with Pollinators: Increasing Profit and Reducing Risk.
d. M. Vaughn, M. Shepherd, C. Kremen, and S. H. Black (2007), Farming for Bees: Guidelines for Providing Native Bee Habitat on Farms.
General Bee Information
There are about 4000 species of native bees in North America, and about 900 species in Utah. A lot of these bees are unfamiliar to many of us. Unlike honey bees, native bees are not aggressive and are unlikely to sting. Even if they do sting, they do not have much venom, and it is not very painful.
Most native bees do not live in colonies; exceptions include bumble bees and some sweat bees. Instead they are solitary, with each female creating her own nest and providing for her own young. About 70% of native bees are ground-nesting, digging tunnels in exposed earth. Many other native species nest in pre-existing cavities in wood, such as soft-centered twigs (e.g., raspberry canes) or the tunnels that beetles leave behind in logs.
There are also about 45 species of bumble bees in the U.S. Bumble bees are social, but do not have persistent colonies, as honey bees do. Bumble bee queens establish new colonies every year in small cavities, such as abandoned rodent burrows. These colonies die off in the fall.
Featured Picture of the Quarter
Cooley spruce gall adelgid is primarily a pest of blue spruce. Feeding by the tiny nymphs (called gallicolae, shown at left) in early spring stimulates newly emerging bud growth to swell and form a gall with interlocking chambers. More than 100 nymphs develop within each gall for a period of 2 to 3 months, emerging as fully grown nymphs in late summer that soon molt to winged adult adelgids.
-USU Extension IPM Program image