Researchers work with Maine’s indigenous blueberries

PHOTOS COURTESY OF UNIVERSITY OF MAINE.
Dave Yarborough in a blueberry field with weather monitoring equipment used for irrigation projects.

Ranked second in the United States in blueberry production behind Michigan, the state of Maine is unique because its commercially sold crop is the wild type and not the cultivated highbush blueberry. Maine’s commercial blueberry crop is native to the region and grows naturally in the understory of the forest. Maine tops the world production of wild blueberry.

Maine farmers harvest over 30,000 acres of wild blueberries each year (more than 60,000 acres total), and over 90 percent of the crop is the “Sweet Low” species Vaccinium angus- tifolium. While growers must plant highbush or cultivated blueberries, wild blueberries only require management and harvesting. The indigenous lowbush blueberry spreads vegetatively by underground rhizomes, which sprout new roots and stems. Blueberry “clones” are the shoots that grow from a single rhizome system.

Wild blueberries have lower disease pressure than cultivated blueberries. Greater genetic diversity among wild blueberry clone varieties provides greater disease resistance. The standard two-year pruning cycle provides a year with no fruit, which disrupts disease and insect cycles to reduce pest pressure. Finally, wild blueberries grow in the North, where longer, colder winters and a shorter growing season effectively freeze-dry pathogens, such as mummy berries, and insects that are temperature-dependent. This environment is not conducive to the cultivated blueberry.

Blueberry Hill, the University of Maine’s research and extension facility

In the 1930s, pest problems almost put the industry out of business. A decade later, Maine’s wild blueberry growers prompted the state legislature to provide necessary funding to establish a research station. Blueberry Hill, in Jonesboro, is a dedicated facility where scientists search for solutions to blueberry-related problems. The state’s growers and processors have provided annual funding support for over 60 years.

A research and extension advisory committee, comprised of wild blueberry growers and processors, has been in place since the establishment of Blueberry Hill Farm. The committee meets with the researchers two to three times a year to discuss challenges and opportunities in management and processing of wild blueberries and reviews current results and further studies.

Frank Drummond in the lab with insectrearing cages.

“The research is very much driven by needs and opportunities,” says David Bell, executive director of the Wild Blueberry Commission of Maine. “We then work to secure funding for priority research, not the other way around.”

A combination of grants, state bonds and wild blueberry tax funds paid for a 4,000-square-foot research laboratory and shop at Blueberry Hill, completed in 2005. This new facility provides a modern workspace with conference room, offices, a field ecology lab and a physiology/behavior lab, and a walk-in computer-controlled environmental chamber and cold room. It also supports on-site research, extension outreach and graduate student training.

The team

Frank Drummond, professor of insect ecology at the University of Maine, has worked for 20 years researching the ecology of insects in Maine’s lowbush blueberry ecosystem. He has been studying native bees in blueberry for 15 years and honeybees in blueberry for the past five years. He conducts the majority of his research at Blueberry Hill, but also conducts field research at several blueberry farms. Drummond has developed least-toxic and organic methods of insect pest management.

Two years ago, Drummond began researching colony collapse disorder (CCD) as part of a national research team. One of his projects is to develop economic alternatives to the honeybee for pollination of specialty crops like blueberry. Currently, Drummond is studying bumblebees and native leaf-cutting bees.

David Yarborough, professor of horticulture and extension blueberry specialist, studied weed control in wild blueberries and wrote his doctoral thesis on weed population shifts with herbicide use and weed crop competition in Maine wild blueberries. Yarborough has worked at UMaine’s blueberry research station for 30 years, spending the first 12 years as a research assistant.

Other research faculty include a blueberry horticulturist and a blueberry plant disease specialist.

The research

Since Blueberry Hill Farm opened in the 1940s, key discoveries about the development of thresholds and monitoring by trapping for insects have helped growers improve practices. As a result, the wild blueberry crop has increased fourfold on essentially the same land base. Had this research not happened, Yarborough believes the blueberry industry today would be much smaller. Bell concurs, “Maine’s wild blueberry business would be about one-tenth the size it is today without generations of research and development.”

Frank Drummond with Judy Collins, harvesting research plots.

The goal of the university researchers is to develop long-term economically and environmentally sustainable blueberry production systems. To keep Maine’s blueberry industry working, the researchers’ current scientific focus is improving efficiency and reducing yield-limiting factors. Potential yield-limiting factors include disease populations, weeds, poor nutrition, the presence of turkeys and birds, and irrigation, as rainfall patterns are changing due to global warming. Yarborough says that once a grower strengthens their plants and increases the number of healthy plants, pollination becomes a potential yield-limiting factor. The grower may not have enough native pollinators to reach all the blossoms.

The intent of Drummond’s research on pollination is to provide multiple solutions to long-term viability of the Maine blueberry industry. Drummond has been researching the causes and potential solutions to colony collapse disorder of honeybees, and looking at the impact of insecticides on the health of honeybees and native bees. He also studies methods to conserve Maine’s native bees (of which over 70 species exist) and to manage potentially new commercial pollinators such as bumblebees.

One element affecting the health of colonies is insect pest management. Drummond hopes his work assessing the exposure and impact of current insecticides on honeybees, plus the program run by his research assistant, Judith Collins, that seeks insecticides that are less toxic to bees, wildlife and people, will make a positive difference. The simple fact is blueberries need bees.

“Without bees there is no pollination, and thus no fruit,” warns Drummond, who has been exploring honeybee health and the health of other commercial bees such as the bumblebee. He researches multiple solutions so the relevance of the research will be broad.

Currently, Blueberry Hill’s researchers have found natural products and/or organically approved controls for all but one insect, the blueberry maggot. Drummond says they have some potential least-toxic controls for this insect; unfortunately, these controls are not as effective as standard insecticides and are quite expensive for growers to use. “However,” he says, “we are tireless in our pursuit.”

Yarborough’s team recently completed a four-year project in cultural and organic management. They examined methods such as burning as a cultural management control to help reduce insect and disease populations.

“We found interaction between burning and use of sulfur could increase the yield synergistically,” Yarborough explains. Although burning is expensive, the resultant increase in productivity generates big returns on the investment. Burning creates an environment conducive to the beneficial insects that reduce pest pressures.

Sulfur application on the soil lowers pH to about 4, which creates a more toxic environment for weeds, but a more beneficial environment for the blueberry plants. The acid-loving blueberries are able to pull adequate nutrients out of the soil.

While each method has its own benefits, using either method alone is not as effective as using the combination. “One plus one is equal to three, instead of two,” says Yarborough. “We can lower weed pressure, require lower herbicide inputs, so this helps commercial growers as well.” Yarborough also found disease pressures were lower in the organic versus conventional fields.

Yarborough also found disease pressures were lower in the organic versus conventional fields.

The majority of Maine’s wild blueberry growers run small family farms. Yarborough and Drummond believe their research benefits farms of all sizes, especially those in New Hampshire, Massachusetts, Atlantic Canada and Quebec. Bell credits Blueberry Hill’s comprehensive research program and cooperative extension outreach with helping farmers become more economically and environmentally sustainable.

“The R&D team is also working to improve processed product quality and explore and promote the health benefits of wild blueberries,” says Bell. “The university is investing in communicating the health benefits of blueberries to the public.”

In cooperation with the university, the Wild Blueberry Commission uses this information to help promote the fruit to consumers. Bell believes it’s important to promote the research station’s work throughout the world to prevent health care catastrophes attributable to low consumption of fruits and vegetables. “It is imperative that consumption of all types of blueberries increases appreciably,” he says.

The future of Maine’s wild blueberries

Bell expects his marketing and promotional efforts to affect the lowbush blueberry industry by driving consumer awareness, interest and, ultimately, demand. “As it has over the last six decades, wild blueberry research and development will continue to be the foundation of the success of Maine’s wild blueberry business. We will continue to focus on improvement of integrated crop management practices for growers to ensure we are one of the most sustainably managed fruits in the world.”

Bell believes processing research will ensure a continued high-quality frozen product available around the globe. Meanwhile, health-related research will also help to drive future demand in the marketplace.

Each year, Maine imports 50,000 to 60,000 hives for pollination and is the second largest user of bees. According to Drummond, the current decline in the honeybee population is a threat to the future of blueberry production in Maine and other parts of the country. “We are facing a crossroad,” he says. “If we have a collapse of both managed and native bees, we will not have affordable access to most fruits, nuts and vegetables. I can’t imagine a diet based almost entirely on leafy greens and grains … kind of boring.”

Drummond believes that the research he and his team are doing today will result in sustained ecosystem function of the wild low-bush blueberry. As he explains, “This marvelous natural North American native crop is not planted, but is a natural understory plant of the Acadian and boreal forests, and one that relies totally on insect pollination.”

Drummond is working to create a future with a strong pollinating honeybee industry presence nationwide, an abundant and diverse species of native pollinators in Maine, and viable economic alternatives to the honeybee, so farmers of all sizes and types of operation can tailor their own pollination strategy. Above all else, he envisions an ecologically sustainable, functioning agro-ecosystem.

Maine growers consistently harvest 70 million to 80 million pounds of Vaccinium angustifolium per year, depending on weather conditions. Yarborough hopes his research will continue to allow Maine to compete with Canada’s rapidly growing wild production and cultivated production throughout the world. “We are opening up more land here, but it takes about 10 years to get lowbush into production.” (In comparison, it takes three to five years to bring highbush into production.)

According to Yarborough, areas that were inhospitable 20 years ago are suddenly suitable for blueberries. “With global warming, there’s no frost, so [farmers can] go into less traditional areas.” Today, growers in Maine get consistent harvests from lands that were frost-prone.

Yarborough, Drummond and the University of Maine’s research team will continue investigating efficient ways to produce and process wild blueberries. Meanwhile, Bell and the Wild Blueberry Commission will continue searching for better ways to market the crop. Yarborough expects that all of these forces working together will manifest a healthy future for the wild blueberry industry. “We are only going to continue to learn more and do better,” he exclaims.

The author is a freelance writer based in Massachusetts and a monthly contributor to Growing.