To fully appreciate the damage invasive species can do to West Virginia's natural resources, look back to the years that began the current decade:
From 2000 to 2003, gypsy moth caterpillars stripped the leaves from more than 1 million acres of West Virginia forestland. When trees lose foliage, they often die. During that grim three-year onslaught, trees - particularly valuable oaks - perished by the thousands. Forestry officials valued the lost oaks' saw timber and pulp at $3.76 million.
And it all happened because a scientist wanted to breed a better brand of silk-spinning caterpillar.
In 1869, French scientist Leopold Trouvelot brought gypsy moths to Massachusetts from Europe. Trouvelot hoped to crossbreed the hardy species with silk-spinning species less resistant to diseases. A few of the gypsy moths escaped from the laboratory, and have expanded southwestward at 5 to 10 miles a year ever since.
In 1972 they entered West Virginia. Defoliation began in 1985 and peaked in 2001. Because gypsy moth populations tend to peak in eight- to 11-year cycles, foresters expect another peak any time now.
"You're going to continue to see gypsy moths be an issue in West Virginia," said Clark Haynes, assistant director of plant industries for the state Department of Agriculture. "Populations are down right now, but tend to build up during drier weather. We think we'll see another defoliating outbreak within the next two to three years."
Scientists have come up with several ways to control gypsy moth numbers. Gypchek, a virus that exclusively affects the species, is effective. So are BT, a bacterium; and Entomophaga, a fungus. Other approaches include Dimilin, a chemical pesticide; and artificial sex scents that confuse male moths and keep them from breeding with females.
"But all those need to be sprayed, and widespread spraying is expensive," Haynes said. "It's hard to justify spraying until populations get almost to defoliating levels."
Among West Virginia's most vivid signs of spring are the dogwood trees that blossom in spring along the state's highways. In recent years, though, dogwoods have been dying, laid low by a fungal disease called dogwood anthracnose.
"It's been found all over West Virginia, in every county," said Haynes. "It spreads from tree to tree by way of spores that ride the wind. It infects trees through their foliage. The leaves develop necrotic sores that spread and cause them to shrivel up. The necrosis spreads down into the twigs. The twig die-back progresses to the branches and the main stem, and the trees die. It takes three to five years for the disease to run its course."
Haynes estimates that West Virginia has lost 50 percent of its native dogwoods since the disease was discovered here in the mid-1980s.
Researchers still aren't sure where or when the disease got started in the United States. They do know, however, that it takes a lot of work to protect unaffected dogwoods.
"Commercial fungicides are effective against it," Haynes explained. "The key is treating the trees early enough. That means getting the fungicide on the tree as soon as the leaves emerge. It takes several applications to do the job."
Forest officials worried for a time that anthracnose might ultimately kill off all of the state's dogwoods. Since then, however, it's become clear that the disease is more likely to strike in damp coves and stream bottoms than on high, dry slopes.
The Mountain State's native hemlock trees are in danger, too, from a little-known insect known as the hemlock woolly adelgid.
"It's an aphid-like insect," explained Tim Tomon, forest entomologist for the state Department of Agriculture. "They only move right after they hatch from their eggs. After that they attach to the needles of hemlock trees and stay there the rest of their lives."
They suck sap from the trees they're attached to. When enough adelgids siphon enough sap for enough time, the trees die.
Tomon said the adelgids currently wreaking havoc on Mountain State hemlock stands originated in East Asia.
"They're believed to have come in on nursery stock from Japan sometime in the 1950s," he explained. "They were first discovered near Richmond, Va. Since then they've spread from Maine to Georgia and as far west as Cabell County in West Virginia."
Infestations have been reported in 35 of West Virginia's 55 counties.
"If you go up into the eastern part of the state, on the other side of the Allegheny Front, most of the hemlocks are dead. There are patches here and there where that isn't the case, but by and large we're losing our hemlocks."
Forest officials are particularly concerned for Preston County's Cathedral State Park, a 133-acre stand of ancient hemlocks.
"We're treating the whole park, but there are a lot of trees that already have lost their lower limbs," Tomon said.
Treatments with the chemical pesticide Imidacloprid are effective, but expensive. Researchers are currently trying to introduce a beetle, Laricobius nigrinus, that preys on adelgids.
"For right now, I'd say the prognosis for our hemlocks is pretty poor," Tomon said. "If (the beetle treatment) takes off, the outlook would be better."
With ash trees comprising just 2 percent of West Virginia's forests, one might imagine that an invasive species deadly to ash trees would be considered a minor threat.
Not so, says Tomon.
"It's a major concern for the folks associated with the New River Gorge National River," he explained. "There are some pretty good stands of ash down there, and once those trees die, the park's officials will have to spend a lot of money to cut them down. If they don't, the trees will become hazards to hunters, hikers and other people who spend time in the woods."
Tomon makes no bones about it - trees infested with the pest will die.
"The published research now says the mortality rate (from ash borers) is 100 percent," he said.
Native to China, the bright-green insects came to the Detroit area in the late 1990s, transported there in wooden packaging material. They quickly spread, and are now found as far eastward as eastern Pennsylvania.
"We first found them in 2006," Tomon said. "So far we've found colonies in Fayette County, in Morgan County and in Roane County."
Officials suspect the insects arrived in firewood brought to campgrounds by out-of-state visitors. Bans on importing and exporting firewood have since been imposed, but Tomon believes the proverbial horse has already fled the barn.
"The only effective treatment so far is a chemical known as EAB -emamectin benzoate. It can protect a tree for three to four years, but it's expensive and it has to be professionally applied. That puts it out of the average person's range," Tomon said.
Invasive species often catch resource officials off-guard. Two species already found near West Virginia's borders - Asian carp and northern snakeheads - will likely become exceptions to that rule.
"We're pretty concerned about Asian carp," said Bret Preston, the Division of Natural Resources' fisheries chief. "We're not sure anything can be done to stop them."
Introduced to control plankton populations in Mississippi's commercial catfish-breeding ponds, two carp species imported from Asia escaped and entered the Mississippi River watershed. In some areas, they've taken over.
"The big concern is that they tend to out-compete other filter-feeders," Preston explained. "When they do, they ruin the base of the food chain and have a huge impact on food availability for other fish species."
One of the species, the bighead carp, has already been found in the Ohio River as far north as New Martinsville. Preston said he's "pretty surprised" that the other species, the silver carp, hasn't yet shown up.
"Those could become really worrisome, especially to boaters on the Ohio," he said.
When startled by boats, silver carp often jump several feet into the air. Jumping carp have injured dozens of fishermen and pleasure boaters, particularly along the Mississippi and Illinois rivers.
Preston also worries that northern snakeheads, also known as "Frankenfish," might find their way to the Mountain State.
"Snakeheads are already in the Potomac River watershed, but so far they haven't made it upstream of the Great Falls of the Potomac," he said.
Also native to Asia, northern snakeheads are voracious predators that will eat just about anything they can sink their teeth into. Preston believes they could wreak havoc on game fish in West Virginia streams.
"The saving grace is that fishermen are learning how to recognize them," he said. "That means there's far less chance that they'll be brought here in someone's live well or bait bucket."
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Information from: The Charleston Gazette, http://www.wvgazette.com
