Agriculture Contributes to Wild Pollinator Decline

Jane Sooby

Has a group of bumblebees burrowed into your compost heap? Have alfalfa alkali bees embedded themselves into a bare spot in your backyard?

If so, don't fetch the kerosene. You are providing habitat to the most useful wild creatures this side of earthworms.

The role of pollinators is possibly the most taken-for-granted element in plant production. Most flowering plants reproduce sexually, requiring the transfer of the male pollen from one flower to the female egg of another flower. Many plants have evolved strategies to attract an insect partner that effects this fertilization, or pollination. This is why so many plants have showy or aromatic flowers. Bees, butterflies, moths, flies, beetles, hummingbirds, and even bats act as pollinators.

Many farmers have noticed a decline in the number of wild pollinators visiting their orchards, gardens, and fields this year. Part of this decline is due to the weather. The fate of many wild pollinators depends on the survival of a single individual, a mated queen, who overwinters and emerges in spring, looking for a source of nectar while she builds a nest. Spring sprung this year only to be followed by three weeks of cold, wet weather. If the queen can't find a source of nectar after she emerges, she will die before producing the next generation.

Honeybees, which overwinter in colonies, have an advantage in this respect. Numbers of wild honeybees have been declining over the last decade, however, due to the spread of the varroa mite. This mite attaches to bees and sucks their blood, like deadly ticks. The varroa mite is devastating wild and domesticated honeybee populations nationwide.

The most widely grown crops in Nebraska do little to support wild pollinator populations. Corn, wheat, millet, and milo are all in the grass family, which depends on wind activity for pollination. Soybeans are not particularly attractive to pollinators. The crops that depend on pollinator activity-mostly by bees-are sunflowers, canola, and legumes like vetch, alfalfa, and clover.

Wild pollinators are important in fruit orchards. Apples, cherries, plums, and pears depend on them to set fruit. Home gardens rely on pollinator activity, too. Vine crops like cucumbers, cantaloupes, squash, and melons need pollinators to produce fruit. Pollinators help provide food for wildlife by assisting fruit production in plants that they eat, such as wild plums, elderberries, partridge peas, vetch, and gooseberry.

Marion Ellis, assistant professor of entomology at the University of Nebraska-Lincoln, says that increasing agricultural activity in the state has contributed to a wild pollinator decline. "A lot of wild pollinators aren't there in the numbers they were a couple of years ago because of the habitat loss," he commented. Ellis believes that installing center pivots into areas that were previously rangeland, removing shelterbelts, and planting large areas to crops unattractive to pollinators have reduced both habitat and forage available to wild pollinators.

Because most crop species have been introduced to Nebraska, wild pollinators aren't as important to crop production as they are to orchard, garden, and wildlife food production. Managed honeybees are more significant pollinators of crop species. They are interested in a broad range of pollen types, while native wild pollinators tend to specialize in the kinds of flowers they service.

Dr. Ellis expresses concern about the declining number of managed honeybee hives in Nebraska. "In the 40's, every fourth or fifth farm kept bees. Now we have just a few large producers keeping most of the bees in the state." The number of managed honeybee colonies in Nebraska has declined 50% in the past decade. This decline is due to low market prices for honey and intensive management requirements for honey production.

People can help increase wild pollinator populations by creating attractive nesting sites for them. Nest boxes, compost heaps, and flowers with deep corollas attract bumblebees. Leafcutter bees require some kind of tube to nest in, and will settle in boards with holes bored in them or even soda straws stuck into milk cartons. Alfalfa alkali bees and other ground-nesting bees are attracted to bare spots on the ground.

Dr. Ellis teaches an annual three-day course in basic beekeeping. This course is presented in the counties from which the largest number of inquiries regarding bees have been made. For further information on wild pollinators or managing honeybee colonies, contact your local county extension office.

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