The steady westward march of the gypsy moth continued into Minnesota this summer with the leaf-eating insects infesting North Shore forests more than ever.
The Minnesota Department of Agriculture reported a record number of moths trapped in the state, more than double the average of recent years.
Minnesota's moth count generally has ranged from 200 to 400 moths trapped each year, with a high of 953 in 1998. This year, crews captured more than 1,000 moths, and they're still counting.
The biggest problem appears to be along the North Shore in Cook and Lake counties, said Kimberly Thielen Cremers, the state's gypsy moth program coordinator.
"Cook County had more than 700, so they really are concentrated there," she said.
Officials are puzzled about the reason Northeastern Minnesota has become such a moth hot spot. Scientists had expected the moths to slowly move through Wisconsin and into eastern Minnesota, especially in the Twin Cities.
The moths now appear to have skipped over parts of eastern Minnesota and established a foothold in the north. Few moths have been found this year in southern Minnesota, with only one small outbreak in the Twin Cities.
"We didn't really expect the north to be the hot spot, but that's where we're most concerned now," Thielen Cremers said.
Not only do the moths slowly move west on their own, but they are transported across the country by unsuspecting tourists and truckers or Northlanders who visited or camped in infested areas to the south and east.
That could be what's brought more moths to the North Shore, said Kris Reichenbach, spokeswoman for the Superior National Forest.
"The egg masses might have been laid last summer (2004) on canoes, boat trailers, recreation vehicles or even firewood in infested areas and brought into the area this summer where they hatched into moths," Reichenbach said.
"We want to use this opportunity to remind people to look for egg masses on anything that might have been stored outside in areas where gypsy moths already have become established."
A thorough, high-pressure car wash usually removes the moth eggs -- especially from wheel wells, a favorite hiding place.
Last year so many moths were trapped near Tower that crews this spring used airplanes to spray a bacteria to kill moth caterpillars. It was the first eradication effort in northern Minnesota. So far, that spraying appears to have worked, with no moths trapped in that area this summer.
Crews probably will spray in hot spots along the North Shore in late May or early June, Thielen Cremers said. Or they could wait for the moths to hatch and then spread synthetic moth pheromone flakes in the area to confuse their ability to mate. Both the bacteria and pheromones have been effective in reducing and even eliminating small and moderate moth outbreaks.
Before hatching into moths in midsummer, gypsy moth caterpillars can defoliate large sections of forest, with oak, aspen, birch and willow among their preferred meals. They eat more than 300 tree and bush species.
Because the moths are an exotic species, there are few if any natural enemies to slow or stop them. And, unlike forest tent caterpillars which cycle up and down, gypsy moths can remain strong year after year, even defoliating trees repeatedly and stressing forests. Some trees can be hit more than once in a single season.
In some cases, tree growth can be slowed and trees already stressed by other causes can be killed. One Wisconsin study showed up to 20 percent of defoliated trees died.
"Every year we can keep them out, it's an economic and environmental success," Thielen Cremers said. "Trees that are putting all their energy into re-leafing can't grow, and that affects the forest and the timber industry."
Gypsy moths are a huge forest health issue in the eastern U.S. and could become a big issue here, affecting where local wood and forestry products can be marketed. Federal laws prohibit some products from infested areas from being sold in uninfested areas.
The moths hit the eastern U.S. from Europe in the 1860s and have been moving west ever since. They are firmly established as near as central Wisconsin. Crews have been spraying in Northwestern Wisconsin's Chequamegon-Nicolet National Forest for the past several years hoping to slow the moths' spread.
The Minnesota Department of Agriculture placed more than 17,000 small cardboard moth traps across the state this year with a pheromone attractant in each. Moths fly into the traps but can't get out, allowing survey crews to see where moths have taken hold.Duluth News Tribune
