May 12, 2013

Maine scientists envision changing forests

A warming climate makes the state's trees vulnerable to pests and other stresses that could imperil its 30,000 forestry-related jobs, experts say.

By North Cairn
Staff Writer

(Continued from page 2)

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Maine's forests generate more than $5 billion a year to the economy through the production of timber and wood products. Tourism and recreation jobs also depend on the health of the forestry industry.

Maine Sunday Telegram file/Gordon Chibroski

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Charlene Donahue, a forest entomologist with the state of Maine, and ecology technician Natashia Manyak of the University of Massachusetts at Amherst released parasitic flies at Two Lights State Park in Cape Elizabeth on Thursday in an effort to help control the winter moth population and minimize its damage to trees and shrubs.

Gabe Souza/Staff Photographer

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• BROWNTAIL MOTH – Larvae feed on the emerging foliage of oak, apple, birch, cherry, hawthorn, rose and other hardwoods, emerging from overwintering webs in late April, even before buds have broken. They continue to feed on leaves and molt hairy skins through June. At that point they pupate, leaving their final skin behind. They defoliate trees and cause branch dieback and tree mortality, and the hairs of the larvae make many people’s skin itchy.

Populations are still low in except on  a couple of areas in Brunswick, in which populations remain high, say state entomologists.

Pruning out webs and destroying the larvae by placing them in soapy water, or clip affected branches by the end of April. Specific regulations apply to for controlling browntail moth near coastal waters. Be sure to check on the current Board of Pesticide Control regulations before treatment.

• EASTERN TENT CATERPILLAR – Webs appear be on the increase this year. In Kennebec County, webs are nearly baseball-sized. Look for the tents of this caterpillar at branch-junctions, especially in cherries, crabapples and other fruit trees, in which they can be a concern, and twist webs off the branches with a forked stick or can be clipped and deposited in a bucket of soapy water. Remove caterpillars as well as the web, but do not burn the webs in trees.

• EMERALD ASH BORER – The emerald ash borer is a small invasive beetle from Asia that has destroyed millions of ash trees since being discovered in the U.S. in 2002.  To date, it has been found in 19 states, and Ontario and Quebec, Canada.  It has not yet been found in Maine, but it is expected to move north from New Hampshire.

The Maine Forest Service is again conducting an extensive survey for EAB using purple sticky traps.  The Division of Plant and Animal Health, the Penobscot Nation, and the U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine (USDA APHIS), will be hanging over 860 traps throughout the state. The color and scent of the trap are attractive to flying adult emerald ash borers, which get stuck in the glue on the outer sides of the trap. 
The purple traps are non-toxic and pose no risk to humans, pets or wildlife. However, the glue is sticky and messy, so it is best to avoid handling traps. If you see a purple trap on the ground in Maine, leave it where it is and contact the forestry service by calling, toll-free, at 1-800-367-0223.

• GYPSY MOTH – Larvae have begun to hatch in southern Maine, and the moths are now found in the southern two-thirds of the state. Continued dry weather would likely reduce one of the moths’ important natural enemies – a fungal disease, Entomophaga maimaiga.

• HEMLOCK WOOLLY ADELGID – This destructive aphid-like insect has decimated hemlock stands throughout the Northeast, but in Maine, with help from a USDA Forest Service grant and support of local organizations, a biological control, the St beetle (Sasajiscymnus tsugae), has been released to attempt to bring the problem under control.

A total of 5,700 of the beetles were released at three state parks –Ferry Beach State Park in Saco, Vaughan Woods State Park in Berwick and Wolfe’s Neck Woods State Park in Freeport – in April. Ten thousand will be released in Cape Elizabeth and Wiscasset during May.

• WINTER MOTH – Found in Harpswell and Vinalhaven last year, green inchworm larva defoliates a wide range of trees, shrubs and plants, especially oak, maple, birch, apple, cherry and blueberry. As the leaves expand, the feeding causes new leaves to appear almost Swiss cheese-like, and, as the infestation progresses, the larvae consume all the foliage. Feeding is completed in early June, and adults emerge from the ground in late November and December, congregating by the hundreds, even thousands, around porch lights and on windows from which indoor light is shining.

-- Maine Department of Agriculture, Conservation and Forestry, Forestry Division

"I think there's fairly good agreement that in Maine we'll be facing a warmer and wetter climate," said Struble. "But I think it's going to be chaotic until things stabilize."

Ironically, some effects -- rising temperatures leading to longer growing seasons and greater precipitation -- will likely improve tree-growth potential, scientists agree. But not for all varieties. The stands of trees people see today are not likely to be the forests that dominate in the not-so-distant tomorrow.

"There won't be much change initially," said Struble, because Maine's forests are populated by mature and resilient long-lived varieties. "Trees themselves will change very slowly; the types will change rather slowly. Trees don't shift that fast, but insects and diseases, they do."


The range, distribution and severity of many pests is climate-controlled, Struble said. For example, the Eastern spruce budworm, one of the most destructive native insects in the northern spruce and fir forests, was first identified in the U.S. in 1807 in Maine and still is seen throughout the northern two-thirds of the state. In its larval stage, it bores into and feeds on needles and buds, finally defoliating the tree.

Its numbers and impact tend to drop off as the insect reaches colder regions toward Hudson Bay. But if temperatures continue to rise here, its range will likely stretch farther north, encompassing more and more of the North Woods.

The southern boundary of the pest might shift northward, too, particularly if winter weather doesn't get cold enough to trigger hibernation, a resting phase essential to the insect's survival.

Non-native invasive pests and diseases already here also appear to be expanding their range.

One obvious sign of the penetration into Maine of formerly unknown pests turned up as clouds of white moths in late fall and early winter last year. Winter moths, which descended on communities by the thousands, have spread here from southern New England, where they have been seen in swarms for many years.

"At this time, the big thing is winter moth," said Charlene Donahue, a Maine Forest Service entomologist. "It's in your face, in your trees."

The moth is active, right now, in its larval form, as caterpillars in buds, she said. Within the next few weeks, people will begin to see some defoliation of trees and bushes, including apples, blueberries and cranberries.

Last week, state entomologists from the forestry division of the Maine Department of Agriculture, Conservation and Forestry began releasing parasitic flies in Cape Elizabeth and Harpswell to try to control and minimize the damage to trees and shrubs done by the moth, said Donahue.

It will be years before entomologists know whether the flies have brought the winter moth under control, but they are hopeful. The moths were used successfully in Nova Scotia in the 1960s, halting the infestation and manifesting no adverse effects over the last 50 years, state entomologists said.

But the clouds of winter moths -- like the continuing spread northward of the hemlock woolly adelgid that attacks both landscape trees and forests -- are signs that weather can have a huge impact on all sorts of vegetation.

 "We're not going to end up with an ecological desert," Struble said. "But the reason to be concerned is that (with climate change), you're going to simplify things for a period of time, and if it gets too simple, it's not as stable. We don't really thrive when things are in collapse. ... It's about having time to adapt to things as things change."

North Cairn can be contacted at 791-6325 or at:


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Additional Photos

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Parasitic flies like this one were released at Two Lights State Park in Cape Elizabeth and in Harpswell last week to help control the winter moth.

Gabe Souza/Staff Photographer


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Today's Poll: Climate change

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