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Emerald ash borer threat looms

By Staff | May 28, 2010

Dutch elm disease was to blame for virtually killing off elm trees in many communities, including Rugby, in the past 20 years.

A new threat is on the horizon.

The Emerald Ash Borer (EAB) has ravaged ash trees in the upper Midwest, spanning from Michigan to Minnesota and leaving forestry officials in North Dakota bracing for its possible invasion.

There are approximately 78 million ash trees in the state, according to the N.D. Forestry Service, and many are located in cities, along river banks and used for shelterbelters, according to Jeff Smette, nursery manager with the N.D. State Nursey near Towner.

“They were so widely planted as a replacement to the American elm,” Smette said.

Rugby has its share of ash trees and Karlyle Erickson, Pierce County extension agent, is aware of the potential threat of EAB.

“It’s not something we’re too concerned about at the moment, but that can change,’ Erickson said.

The majority of species of ash trees in North America appear to be at risk to the dark, metallic green beetle which is about one-half inch long. Adults emerge in May thru late June. Female begin laying eggs a few weeks after emerging.

The eggs hatch after two weeks and the tiny larvae bore through the bark and into the cambium – the area between the bark and wood to feed for several months.

The trees leaves begin to thin above the infested portions of the major branches since the borer destroys the water and nutrients in the tissue under the bark. The canopy will be dead within two years.

The wood boring beetle was first discovered in 2002 in Michigan, but how long it has been in the upper Midwest is uncertain. It didn’t take long, unfortunately, for it to spread.

One likely scenario for its rapid migration was infested ash trees which were cut down, and the logs for firewood were brought into other areas free from the beetle. To date, it’s killed off 30 million trees.

Smette said what could help N.D. in the battle against EAB is the wide open spaces. However, urban areas and river cooridors where the ash tree is planted could be thinned out.

Many forestry officials and landscapers have encouraged people to plant other species of trees in the future.

“We’re learning from past mistakes and that means to diversify the species we plant,” said Smette.

Also, city forestry departments have plans in place to quickly take down infected ash trees to prevent the beetle from spreading to healthy trees.

Smette said while green, white and black ash are susceptible to EAB, the mountain ash, which is not a true ash species, has not been affected. There is also reports now that the Manchurian ash appear to immune from the beetle.

Erickson pointed out ash trees around here have already have contended with an ash borer.

“This particular one tends to go in cycles and is not as aggressive (as the EAB),’ he said. “However, it can still do quite a bit of damage, killing of branches and boring into the bark, leaving channels.”

Residents with ash trees may soon notice some leaves dropping or curling once warm weather returns. Erickson said a warm up following a cool rainy period at this stage of spring often leads to ash anthracnose, a type of fungus. The best way to manage the disease is to prune dead or dying branches and dispose of all the leaves and other debris in the fall.

Sources: www.emeraldashborer. info

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