October 2, 2012

Global warming aids Maine cranberry crops, says expert

By North Cairn ncairn@pressherald.com
Staff Writer

Maine's cranberry harvest is up this year, and one Cooperative Extension specialist thinks warmer weather brought on by climate change might be one reason for that.

click image to enlarge

Raymond Lilly, left, and Jimmy Smith rake cranberries towards a pump intake as they do a wet harvest on Tuesday afternoon at Popp Farm in Dresden.

Staff photo by Joe Phelan

click image to enlarge

Jimmy Smith rakes cranberries on Tuesday afternoon at Popp Farm in Dresden.

Staff photo by Joe Phelan

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Charlie Armstrong, a cranberry specialist with the Cooperative Extension at the University of Maine, in Orono, said warming weather since the mid-19th century -- an average 1.5 to 2 degrees Fahrenheit globally -- may be a harbinger of changes to come for agriculture statewide.

If the average temperature were to rise even a couple more degrees, he said, the difference could be significant, opening up parts of Maine to crops such as peaches, ordinarily grown as far south as Georgia, where the peach is the signature fruit.

Maine peaches now are so rare they almost qualify as exotics. They are grown only in small numbers in semi-rural areas such as Albion and Bowdoin.

"I never thought it would be possible to grow peaches in Maine," Armstrong said. One grower has even decided to plant kiwis.

In contrast to peaches and kiwis, Maine cranberries, which represent a mere 1 percent of the nation's total crop, seem like a large-scale agricultural staple.

Armstrong said the 2012 cranberry harvest, which begins this week in many bogs, is expected to yield 25,000 barrels, or 2.5 million pounds, from a total of only 210 acres of beds and bogs statewide. About half are in Washington County.

This year's yield is still slightly less than that of the "best ever" year, 2010, when more than 29,000 barrels were harvested, Armstrong said. It exceeds last year's crop of about 23,700 barrels -- and final results are not yet in.

Despite an increase in troubles this year with such pests as worms and moths, cranberries "are looking super, overall," Armstrong said. The cranberry fruitworm population was high this year -- as much as three times more than normal -- but even the most seriously affected growers lost only 5 percent to 10 percent of their crop.

Armstrong blamed the mild winter for high fruitworm and moth populations. More balmy temperatures "favor the over-wintering stage, halfway between the larva and the moth," of the cranberry fruitworm, a pest that can devastate the crop.

A fungus known as root rot also caused an incremental loss in yield this year -- about 1 percent statewide, which is typical, he said.

In many respects, climate change could "prove beneficial," Armstrong said. A further rise in temperature could harm growers in states such as Massachusetts and New Jersey, traditionally big producers, and that probably would mean conditions in Maine would be more favorable for the berries, which can tolerate the warmer temperature but prefer cool nights.

On the flip side, such weather changes also could be a boon to insects, Armstrong said, adding, "For some growers, it might be more of a headache, because there might be more pests."

It's a problem that cranberry growers here struggled with during the growing season in the form of cranberry fruitworms and fruit rot, along with the threat of a new species of fruit fly, the spotted-wing dropsophila.

However, "narrow chemistries" in newer pesticides, which have replaced many of the more deadly organophosphates, helped keep yield up by eliminating pests that ordinarily take as much as 40 percent of an untreated crop, Armstrong said.

The two newer treatments -- Bt, or Bacillus thuringiensis, and Entrust -- have made a big difference in controlling "the highest fruit worm population I've seen in 10 years," Armstrong said. Bt -- a toxic crystal pesticide first identified in the early 1900s -- now serves as a horticultural poison with residual toxicity lasting, at most, three weeks. It became part of the commercial chemical arsenal in the 1950s and in recent years has been part of genetically modified plant strategies, in this case to get plants to produce the bacterium on their own. Scientists are not certain how it works.

(Continued on page 2)

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Additional Photos

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Cranberries float in a flooded field on Tuesday afternoon at Popp Farm in Dresden.

Staff photo by Joe Phelan


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