PA Farm News
April 9, 2008
Understanding Bumblebees: Making a Case for Conserving Native Pollinators
By Alex Surcia, Penn State Cooperative Extension
Research
Assistant
CARLISLE-- Why is pollination important?
A healthy economy and sustainable communities rely on local food production and availability. Over the last three decades, American agriculture has industrialized explosively; the result is that fewer but larger farms specialize in a handful of crops. This change has been driven by many factors, including the demands of feeding a growing population and the simple economics of production. Urban sprawl and “factory” farms have resulted in a rapid loss of plant and animal diversity. Populations of insects have declined. Why is this a problem? Insects pollinate 75% of our crop plants, and only if properly pollinated can plants produce high-quality seeds, fruits and vegetables.
The nonnative honeybee has become the American farmers’ favorite pollinator. Introduced from Europe 400 years ago, the honeybee spread rapidly in the 1940s when migratory beekeepers began to use American highways. A 1998 census estimated that 2.9 million honeybee colonies were present in North America, and 2.5 million of those were rented for pollination. Cornell University researchers recently estimated the pollinator services of honeybees for food crops at $15 billion annually.
Most people ignored the continuous decline in native pollinators, such as the bumblebee, blaming the weather or lack of fertilizers for poor agricultural yields. But in the past decade the honeybee population declined 25%, mainly due to the bees’ exposure to pesticides, exotic diseases, and parasites. An even more serious threat to U.S. agriculture came in 2006, when in 24 states Colony Collapse Disorder decimated up to 80% of honeybee colonies. This epidemic clearly demonstrates that to rely on a single species of bee to pollinate much of the nation’s food is risky. Attention has turned to the native bees as alternative to the honeybee.
What is pollination?
Pollination is the first step in creating a fruit or vegetable. Pollinating agents, such as bees or wind, transfer pollen from the male parts of a flower (anther) to the female parts (stigma). Only when compatible pollen reaches the stigma is pollination successful. Eighty percent of pollinators are insects; the wind causes pollination about 20% of the time, and water less than 1%. Bees are the most significant pollinators. More than 4000 bee species exist in the Eastern United States. A native bee, the bumblebee is a more efficient pollinator than the honeybee because bumblebees can tolerate inclement weather better, and because they buzz-pollinate by shaking the anthers, thus releasing more pollen.
How many types of pollination exist?
Self-pollination occurs when pollen is transferred within a single flower without an agent. Exceedingly rare, this pollination is found in flowers whose anthers touch the stigmas before the flower opens. Self-fertility (self-pollinating) is the flower’s ability to set fruit if an agent brings pollen from the same plant. When the flower sets fruit with pollen from a different plant, cross-pollination results. Cross-pollinated plants acquire more diverse genetic information, enhancing the plant’s ability to adapt to continuous environmental changes. Often, by modifying its flower features the plant evolves to reward fewer, or just one, pollinator species — thus making access harder or impossible for other pollinators. With less competition, specialized pollinators are motivated to forage between plants of the same species, cross-pollinating them. Unlike honeybees, bumblebees do not communicate flower location with each other. This increases the chances that bumblebees will concentrate on the same crop. Moreover, the individual bumblebee specializes in certain plants, usually “majoring” in a particular flower, with a back-up “minor” flower in case the main source is exhausted. This specialization increases the success of cross-pollination.
How can we conserve native pollinators?
Native bees, especially bumblebees, thrive in environments containing a variety of plants. The bumblebee colony needs a constant source of food, and through the winter only the young queens survive. The ideal environment is diverse, balancing long-blooming native plants with other plants that attract bumblebees. Generally, plants hybridized to produce more blossoms, or blossoms of different sizes or colors, are poor foraging sources. Pesticide-free and unmowed patches of grass and “islands” of trees offer much needed nesting habitats for pollen bees. Less manicured gardens provide a more welcoming environment for bees. Plant and bee diversity is crucial for agricultural success.
By Alex Surcia, Penn State Cooperative Extension
Research
Assistant CARLISLE-- Why is pollination important?
A healthy economy and sustainable communities rely on local food production and availability. Over the last three decades, American agriculture has industrialized explosively; the result is that fewer but larger farms specialize in a handful of crops. This change has been driven by many factors, including the demands of feeding a growing population and the simple economics of production. Urban sprawl and “factory” farms have resulted in a rapid loss of plant and animal diversity. Populations of insects have declined. Why is this a problem? Insects pollinate 75% of our crop plants, and only if properly pollinated can plants produce high-quality seeds, fruits and vegetables.
The nonnative honeybee has become the American farmers’ favorite pollinator. Introduced from Europe 400 years ago, the honeybee spread rapidly in the 1940s when migratory beekeepers began to use American highways. A 1998 census estimated that 2.9 million honeybee colonies were present in North America, and 2.5 million of those were rented for pollination. Cornell University researchers recently estimated the pollinator services of honeybees for food crops at $15 billion annually.
Most people ignored the continuous decline in native pollinators, such as the bumblebee, blaming the weather or lack of fertilizers for poor agricultural yields. But in the past decade the honeybee population declined 25%, mainly due to the bees’ exposure to pesticides, exotic diseases, and parasites. An even more serious threat to U.S. agriculture came in 2006, when in 24 states Colony Collapse Disorder decimated up to 80% of honeybee colonies. This epidemic clearly demonstrates that to rely on a single species of bee to pollinate much of the nation’s food is risky. Attention has turned to the native bees as alternative to the honeybee.
What is pollination?
Pollination is the first step in creating a fruit or vegetable. Pollinating agents, such as bees or wind, transfer pollen from the male parts of a flower (anther) to the female parts (stigma). Only when compatible pollen reaches the stigma is pollination successful. Eighty percent of pollinators are insects; the wind causes pollination about 20% of the time, and water less than 1%. Bees are the most significant pollinators. More than 4000 bee species exist in the Eastern United States. A native bee, the bumblebee is a more efficient pollinator than the honeybee because bumblebees can tolerate inclement weather better, and because they buzz-pollinate by shaking the anthers, thus releasing more pollen.
How many types of pollination exist?
Self-pollination occurs when pollen is transferred within a single flower without an agent. Exceedingly rare, this pollination is found in flowers whose anthers touch the stigmas before the flower opens. Self-fertility (self-pollinating) is the flower’s ability to set fruit if an agent brings pollen from the same plant. When the flower sets fruit with pollen from a different plant, cross-pollination results. Cross-pollinated plants acquire more diverse genetic information, enhancing the plant’s ability to adapt to continuous environmental changes. Often, by modifying its flower features the plant evolves to reward fewer, or just one, pollinator species — thus making access harder or impossible for other pollinators. With less competition, specialized pollinators are motivated to forage between plants of the same species, cross-pollinating them. Unlike honeybees, bumblebees do not communicate flower location with each other. This increases the chances that bumblebees will concentrate on the same crop. Moreover, the individual bumblebee specializes in certain plants, usually “majoring” in a particular flower, with a back-up “minor” flower in case the main source is exhausted. This specialization increases the success of cross-pollination.
How can we conserve native pollinators?
Native bees, especially bumblebees, thrive in environments containing a variety of plants. The bumblebee colony needs a constant source of food, and through the winter only the young queens survive. The ideal environment is diverse, balancing long-blooming native plants with other plants that attract bumblebees. Generally, plants hybridized to produce more blossoms, or blossoms of different sizes or colors, are poor foraging sources. Pesticide-free and unmowed patches of grass and “islands” of trees offer much needed nesting habitats for pollen bees. Less manicured gardens provide a more welcoming environment for bees. Plant and bee diversity is crucial for agricultural success.
Penn State is committed to affirmative action, equal opportunity, and the diversity of its workforce. Penn State Extension in Cumberland County is located at 31 Allen Road, Suite 601, Carlisle, PA17013, phone 717-240-6500 or e-mail
cumberlandext@psu.edu.
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