DEBLOIS, Maine — By 7:30 on a surprisingly chilly August morning, workers on the rocky blueberry barrens were two hours into their back-breaking rhythm, raking tiny berries from low bushes.
Over and over, they filled hand-held scoops and gently poured the succulent wild fruit into brightly colored tubs stacked high on the expansive fields— the first of more than 80 million pounds of berries expected to be harvested and frozen in the next few weeks and shipped the world over to fill muffins, pancakes, pies, and breakfast bowls.
This year’s crop is threatened, however, by a red-eyed, weak-flying fruit fly that has soft-fruit farmers across the United States scrambling to protect not just blueberries, but raspberries, blackberries, and late-season strawberries. The spotted wing drosophila, an Asian fly found in California in 2008, first showed up in New England in 2011. In 2012, an estimated 2 million pounds of wild Maine blueberries alone, worth close to $1.4 million, were lost, according to eFly, a consortium of researchers and farmers studying the pest.
Now growers here are bracing for the invasive fly’s return this month and worrying that the infestation could intensify and spread.
“It’s a very scary pest,’’ said Judy Collins, assistant scientist at the University of Maine School of Biology and Ecology. “It attacks so many different fruits. Once its population really gets going, it increases so rapidly . . . it can cause terrible losses.”
On Maine’s blueberry barrens, Cherryfield Foods, Maine’s largest blueberry producer, brought in 44 extra mechanical harvesters to pick all the fruit before the fly population explodes. Other farmers are hiring more pickers or trying to ramp up their freezing operations.
Some small New England growers have been hit so hard in the last two years that they have stopped growing raspberries — one of the pests’ favorite fruits — to save their business and slow its spread. But most are confronting an unenviable choice: Accept that vast amounts of the harvest could be infested with maggots, or apply pesticides more frequently to control the flies. Neither is an image any grower wants to portray to the public. Scientists say fruit sold in stores is safe: Farmers can identify and destroy infested fruit, and there are limits on how much pesticide can remain on fruit before it is sold.
Entomologists say they cannot predict the fate of the thousands of backyard raspberry patches and blueberry bushes in the region. They are asking homeowners to be vigilant for telltale mushy fruit and, while there is debate about whether it will really help with such a pervasive problem, some suggest bagging and sealing any infested fruit before throwing it away. The fly is also found on commercial and backyard crops of cherries, tomatoes, and other fruits.
The pest may look familiar: It is technically a vinegar fly, those pesky bugs found in kitchens that attack overripe or diseased fruit. But this fly is a “game changer” said Sonia Schloemann, University of Massachusetts Amherst Extension fruit specialist, because the females are equipped with a razor-like appendage that allows them to slice into healthy fruit to lay eggs, often close to harvest time. The fly’s rapid reproduction rate — 10-12 generations in a year — and the suddenness of its appearance make it even more worrisome.
“Growers are disappointed,’’ said David Bell, executive director of the Wild Blueberry Commission of Maine. “Through investing in university research and hard work we were really able to get our insecticide use down to next to nothing.” For example, blueberry growers have learned to deal with a native blueberry maggot by understanding its life cycle, rigorously looking for it, and using pesticides sparingly to kill it.
“What spotted wing requires us to do is to start all over,’’ said Bell.
The wild blueberries are quite different from the cultivated ones usually sold in supermarkets, and not just because they’re tiny. The plants have crept over Maine’s rocky land naturally since the end of the last Ice Age, creating hundreds of thousands of bushes. Other than in Canada and a few scattered locations in New England, they are not found anywhere else in the world.
In the mid-1990s, wild blueberries catapulted into the national health spotlight. Researchers showed they contained large amounts of antioxidants, which are believed to have cancer-fighting properties. Markets were developed overseas, and frozen wild blueberries became part of many peoples’ daily diet.
Invasive species are hardly new on the New England landscape, but many take root slowly, giving the authorities time to prepare and slow, if not halt, their spread. The Asian longhorned beetle, which first appeared five years ago this month in Worcester, has been kept in check in part through aggressive — and controversial — cutting of trees.
But the spotted wing drosophila appeared so rapidly and spread so quickly after being found in strawberries and raspberries in California that it was quickly deemed beyond containment. Trucks and planes likely spread the fly by delivering infested fruit.
“All of us were taken by surprise,’’ said Linda Hoffman of the organic Old Frog Pond Farm in Harvard, Mass. who learned of the infestation two years ago when a customer found the larvae inside raspberries. She closed the patch that year and began using a host of organic pest control methods with “fair success.” Now, her pick-your-own raspberry patch is open, but she explains the problem to customers; most are understanding.
Other Massachusetts farmers are taking a wait-and-see attitude. Ward’s Berry Farm in Sharon put on hold plans to expand its raspberry patch, and employees are carefully watchingwhat other crops the fly attacks this year; Tim Nourse, president of Nourse Farms Inc. in Whately, is spraying more and taking precautions to slow the fly’s spread.
“Before if we had a bad berry, we dropped it on the ground, now we take it out of the field” to prevent the fly from multiplying, said Nourse. The best defense, Schloemann says, is for farmers, pick-your-own customers, and backyard growers to get to all the berries before the flies do.
The flies, a mere one-eighth of an inch in length, can be challenging to distinguish from other fruit flies — University of Maine’s Collins can only identify them under a microscope. She monitors them by placing 16-ounce, red plastic cups filled with a yeast-and-sugar solution at the university’s Jonesboro blueberry research farm. She has only captured a few dozen this year, but if last year is any indication, she will soon be finding hundreds in each cup.
Her team is experimenting to see whether the cups, if placed in large enough numbers, could attract the flies away from blueberries on small farms. Another option is to cover plants with a superfine mesh.
Such efforts would not work on the 60,000 acres of blueberry barrens in Down East Maine, a 3½-hour drive from Portland. But the two largest wild blueberry producers are taking the long view.
As giant mechanized harvesters rolled across the barrens behind him, Ragnar Kamp, chief operating officer of Oxford Frozen Foods, the parent company of Cherryfield Foods, shook his head when asked whether he was very worried.
“Mother Nature always throws something at us,’’ he said.
Ed Flanagan, president and chief executive of Jasper Wyman & Son, said he was confident the company would conquer the pest, but said warming winters because of climate change would help it thrive.
“The best pesticide is a cold winter,’’ he said. “If the fly wins we’ll have reduced yield. . . . But we expect to win.”