David Yarborough: I’d like to give you an overview of wild blueberry production in Maine from the beginning, and to discuss the changes that have occurred and made it a $250 million industry.
Wild blueberries colonized the soil after the last Ice Age receded. The action of the glacier created a well-drained sandy loam soil that blueberries were able to grow in.
As the glacier receded, the land rebounded and early successionary plants, such as blueberry, began to colonize the nutrient-poor soil sites.
The wild blueberry is one of the first plants to become established and were able to survive because of a fungal infection — that is, a mycorrhizal association, where the blueberry plant trades nutrients for minerals with fungi and so have a symbiotic relationship that benefits both of them.
Wild blueberry plants have survived in the forest understory. When the forest was cleared by Native Americans with fire, or by colonists for shipbuilding for timber, this allowed for the blueberry barrens in Down East Maine to become established. Wild blueberries are the low-bush type. There are two different kinds. They grow about 1 foot tall and cover the fields.
We call them wild because these plants occur naturally in Maine, and we manage their growth to improve production. Native Americans used wild blueberry as food. And we began to manage them after the Civil War when berries were sent to feed the Union troops.
Wild blueberries differ from the cultivated blueberry (in the center) and the European blueberry (on the left). The major difference is the size of the blueberries, but wild blueberries also have a more complex flavor, because they are a mixture of many different varieties.
Commercial wild blueberry production is concentrated in Maine, Atlantic Canada and Quebec, with minor productions in New Hampshire, Massachusetts and Michigan.
There’s a large concentration of blueberries covering thousands of acres in Down East Maine called the blueberry barrens. Maine has about 44,000 acres and two of the largest fruit farms in the U.S.
Two early reports by University of Maine researcher Munson describe the industry. The actual acreage now is lots less than it was in the 18th through the 1900s, as these areas were managed by burning over the fields every five or six years.
Early berries were handpicked and shipped in quart wood boxes by schooner and by rail. In 1883, the Tabbut rake allowed for a more efficient harvest. This rake was fashioned after the cranberry scoop.
Berries (were) first canned in 1886, and there were 21 factories by the 1950s. Berries were packed under different labels, with Maine, Colorado and Chicago or New York, but these were all done in Columbia Falls, Maine.
Maine was the largest producer in the 1950s in the U.S. but now only has about 9 percent of the North American crop. Whereas cultivated blueberry production has increased to 66 percent, with now most produced in the Pacific Northwest and southern United States. Wild production has increased from 10 to 100 million pounds over the past 50 years.
Maine had over 100,000 acres but produced only about 10 million pounds in the 1950s. It now produces 100 million pounds on just 44,000 acres, by improving our management practices.
A unique feature of wild blueberries is that they’re pruned on a two-year cycle to get maximum production from the new shoots. Most fields are under 10 acres, and we have about 500 growers.
Plants were burned over by Native Americans, but in the 1940s, fuel oil was used in burners and is still done in some of the rockier fields today. This is dangerous. It pollutes the air, and if fire escapes, (it) can destroy other property.
But the burning process is good in that it does kill some insects and diseases. The need for burning is because of the rocks deposited by the glacier. And these are common in many fields in the coastal area. We now use excavators to remove the rocks and smooth the fields.
When rocks are removed, fields can be mowed and machine-harvested, which reduces the two most-expensive management costs. But we need specialized mowers to follow the contour of the land. This is possible since pruning only takes about a third of the plant.
Stems emerge from the underground portion of the plant, or the rhizome, which makes up the other two-thirds of the biomass of the plant. Fields have hundreds to thousands of clones that range in size from a few feet to a football field in size.
We estimate there are about 4.8 million different varieties in Maine wild blueberry fields.
Weeds are a major limiting factor to production. This is a wild blueberry field without any weed control. Research on weeds and wild blueberries in Maine show the effect of weed cover in reducing yield, going from 5,000 pounds an acre with no weed cover to 1,000 pounds an acre with a 100 percent cover by bracken fern or dogbane.
So, there’s a point to first control the weeds in order to get good production. Weeds also reduce the quality by crushing and mushing the berries when harvested by rake or machine, which reduces the grade and the value of the fruit.
Mulching is another practice that will help us improve plant spread. Mulch retains moisture and reduces the surface temperature in the summer. This provides a better environment for plants to grow and spread and fill in the entire field.
An important cultural management tool is the use of sulfur to reduce soil pH. Blueberries do well at a low pH and weeds thrive at higher pH levels. In this photo, the pH in the center with the bracken fern and St. John’s wort weeds is 6.0, whereas the areas with the blueberries is 4.3.
In the fall, plants turn red. You can see the different-colored clones more easily that time of year.
Plants are covered with snow over the winter, and the buds break in the spring with leaves and blossoms. We use a sweep net to determine if there are sufficient insects to cause damage. And then we would have to use an insecticide to keep them from eating the crop.
Mummy berry is a disease that causes blight on wild blueberry plants and reduces production. Plants must be protected from infections well before the damage is seen. The University of Maine monitors temperature and moisture conditions to provide a forecast to our growers to indicate when they need to spray to protect the plants and prevent yield loss.
Wild blueberry bloom starts at the end of May and continues through the beginning of June. We need bees to pollinate the crop. Wild blueberry pollen is heavy and requires an insect to transfer it. Honeybees are the most common bees to use, but we also import bumblebees and we have many different types of native bees as well.
Note with this graph the strong correlation with the increase in imported bees, which are migrant workers (in red) and the corresponding increases in blueberry yield (in blue). Good pollination will give larger fruit, more-even ripening, and more fruit, but moisture is also needed to improve production as well.
Some growers have invested in big-gun irrigation systems. This one gun will do an acre with the pipe put in underground. Wild blueberries have been using integrated pest management monitoring tools since the early 1970s.
A University of Maine researcher developed the use of the apple maggot trap to determine fly presence and develop thresholds for spraying to improve both the effectiveness and to reduce sprays.
New research by the University of Maine researchers used the understand(ing) of fruit fly biology to reduce insecticide sprays. Since flies emerge on noncrop fields, they must migrate to adjacent crop fields. So now we only use a border spray of 50 feet around the field and so do not have to spray the interior of the field at all, thereby greatly reducing the amount of insecticide needed for control.
Wild blueberries have one harvest every other year. Harvest begins the last week of July and goes through Labor Day. Harvesting the wild blueberry crop is a tradition done by local labor and a few migrants, prior to the crop increases in the 1970s.
Traditional harvest is with a handheld rake. Migrant Mexican labor came to Maine when we began to have larger crops. We now use a larger rake with extended handles to improve efficiency.
Most of the crop is now harvested by machines, which use just one large box and it has lights on it, so that allows for 24-hour harvests.
Small harvester was developed by Maine Blueberry Equipment Company in Columbia Falls, Maine, with a FAME grant. Other small machine harvesters from Quebec are also becoming available. The objective is to process all fruit within 24 hours. There are six processing plants in Maine and others in Quebec and in Atlantic Canada.
First a blower removes the sticks and debris. Berries are sorted by size, so the smaller ones are taken out. Berries are then washed and are frozen after a journey through a freezer tunnel. (They’re) stored in 4-by-4-by-4-foot tote bins that weigh over 1,000 pounds.
Wild blueberries are an ingredient. Traditional uses include muffins, pancakes, pie and cereal.
Wild blueberry was found to be the No. 1 antioxidant fruit. It has anthocyanins, a phytochemical in the fruit, which ties up free oxygen radicals that cause cancer and aging by degrading DNA in our cells.
A Tufts University animal study showed that old rats with a blueberry diet could do as well as young rats in memory and in physical tests.
Blueberries play a role in many areas, including brain and cardiovascular health. They help prevent cancer and can reduce insulin spikes. All you need is to eat a half a cup of blueberries today, or about 4 ounces, to get these health benefits. Smoothies are now the No. 1 use of wild blueberries.
These websites contain additional information of wild blueberry health, where to find wild blueberries, and how to grow them.