Pollination Challenges in Today’s Changing Climate

Pollinators are responsible for nearly 30 percent of our nation’s food supply. Honey bees (Apis mellifera) support an estimated $15 billion in crop production, visiting fruits, nuts and vegetables including blueberries, cranberries, cucurbits, apples, almonds, onions, celery, beets, brassica and citrus. In California alone, 850,000-plus acres of almonds require more than 1.5 million honeybee colonies for pollination. Pollination Challenges

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Yet populations of honey bees and other pollinators worldwide are declining. In the United States, approximately 30 percent of colonies are lost each winter due to the combined effects of pests, pathogens, environmental toxins and poor nutrition. While climate change is not the sole cause of stress to honey bees, the links to climate change are clear. For example, the honeybee pest Varroa mite could produce many more generations in a warm year than in a year with seasonably cool temperatures. University of California-Davis entomologist Elina Niño, Ph.D., said the added presence of the mites stresses honey bees. Niño also expressed concern that California’s ongoing drought has reduced the amount of available forage for the honeybee population. “We’re feeding our bees sugar and protein supplements. It’s becoming more and more expensive to keep the colony going,” she said.

For growers relying on pollination to set their crops, unpredictable weather patterns can lead to unpredictable pollination. Honey bees are most active in warm, sunny conditions, said Cesar Rodriguez-Saona of the Rutgers University Philip E. Marucci Center for Blueberry and Cranberry Research. Intense rain patterns can reduce their foraging behavior.

Zeke Goodband, orchard manager at Scott Farm in Dummerston, Vermont, brings in about one hive of honey bees per acre at the beginning of the blossom bloom. Yet climate change has disrupted the growing season, requiring Goodband to adjust his pollination practices.

In recent years, unusually mild starts have caused the farm’s 120 varieties of heirloom apple trees to break dormancy as much as a month ahead of historical patterns. Subsequent returns to normal cold or freezing temperatures damage apple buds and blossoms. In cold snaps, imported honey bees don’t do the job. “The honey bees seem to have the work ethic of teenagers – start work later in the day, stop earlier and seem to need near perfect conditions to really work,” Goodband said.

Pollination Challenges


Return of the native

Before the advent of trucking honey bees around the country in 1907, produce growers without their own hives relied on wild native bees to pollinate their crops. There are approximately 4,000 species of wild bees documented in the U.S., and today, estimates for wild bee pollination services are at $3 billion.

“Many of our crop plants depend on bees and wild pollinators for fruit set,” reported University of Florida entomologist Glenn Hall on his website The Bees of Florida. Native pollinators can pollinate almost any plant, but they prefer certain plants over others.

In our changing climate, more growers are returning to wild pollinators to ensure the success of their crop. In New Jersey, USDA’s Natural Resources Conservation Service assists local farmers in designing, installing and maintaining native pollinator habitats as conservation practices. Funding for these habitats is available through the various financial assistance programs offered by USDA-NRCS.

In Vermont, Goodband is relying more on wild bees for pollination because they work in cooler temperatures and tolerate wind and wet weather. “Native bees just seem more resilient and able to deal with these changes,” he reported.

In Dedham, Maine, wild blueberry grower Gail VanWart discovered likewise. Long stretches of wet weather during spring pollination had become an increasing problem for VanWart. “Honey bees will not fly when it’s rainy, windy, or when the temperature drops below 50 degrees Fahrenheit,” she said. “Spring is when the bloom comes on the wild blueberries, and they have just a few weeks to be pollinated before the bloom falls off. Any blossom on the wild blueberry plant that does not get pollinated will not become a blueberry.”

VanWart switched from honey bees to native pollinators, so she could count on pollination happening, even in varied and inclement conditions. “We gained insight on how nature intended crops to be pollinated,” she shared in a recent email. VanWart also turned her wild blueberry farm into a sanctuary for native pollinators to exhibit their worth in crop production.

Since making the switch, VanWart has seen increased pollination and, thus, increased yields. Financially, “going native” has been a boon. “Native wild bees do not cost us any time or money to keep, so it is far less costly than keeping honey bees, especially in a northern climate where they have a hard time overwintering,” she said.

Encouraging natives

Anne L. Nielsen, extension specialist in fruit entomology at Rutgers University, manages flowering weeds between trees in apple and peach orchards to reduce the number of bees foraging in the orchard after bloom. “Ongoing research in my lab has been on managing ground cover to reduce pesticide exposure to foraging bees – both honey bees and natives,” she said.

Josh Campbell, a native pollinator researcher in the Honey Bee Research and Extension Laboratory at University of Florida suggested growers make their land as pollinator friendly as possible by:

Following exact label instructions for pesticides to minimize impact on pollinators:

  • Using a no-till practice (even outside of the crops) to enhance native bee nesting structure for the 70 percent of native bee species that are ground-nesters;
  • Planting native wildflowers that bloom at different times to provide nectar/pollen throughout the season, and;
  • “weeds” are highly attractive to honey bees and native pollinators.

To enhance the biodiversity of their orchard ecosystem, Scott Farm planted a plethora of wildflowers and a diverse array of tree fruit, shrubs and vines. “With 120 varieties of heirloom apples we’re pretty well spread out with bloom times and harvest,” Goodband said. “We think our growing philosophy that recognizes the orchard as a potentially wildly diverse ecosystem will help us ‘weather’ the changes in climate.”

In Maine, VanWart makes sure to have native plants around to provide native pollinators a diversified diet from spring to fall. “It is just letting nature do what it was supposed to,” she said.