January 27, 2007

Working to I.D. Foes of Emerald Ash Borer

The emerald ash borer, a major threat to ash trees, may have met the enemy, parasitic wasps.And it's now up to researchers, including those at ARS's Sytematic Entomology Laboratory (SEL), to figure precisely who that enemy is.

"We know of three species of parasitic wasps that are natural enemies of these beetles," says SEL entomologist Michael Schauff, who is based in Beltsville, Maryland. He and fellow entomologist Michael Gates, who works out of SEL's Washington, D.C., facilities, are leading ARS's taxonomic work against the pest.

"But we can't put a name on these potentially helpful wasps without first doing research. We do suspect that some of these species have been unknown to science up to this point."

For more information, go to http://www.ars.usda.gov/is/AR/archive/feb05/borers0205.htm

Photo by Klaus Bolte

Posted by Ron Wolford at 3:19 PM | Permalink |

January 23, 2007

Firewood Unintentionally Transports EAB

Appleby said that even though the pest has been in the news since it was first identified in ash trees near Detroit in 2002, there are still people who are unaware of the problem and inadvertently transport the pest to uninfested areas. "I talked with a homeowner in Michigan who had a number of dead ash trees on her property. She said that she had never heard of the ash borer and didn't know it was a problem." Appleby described an innocent scenario that may occur in which her friend or grandson from Illinois visits and she says, "I have plenty of firewood. Take as much as you want." The wood filled with ash borer larvae, gets thrown into the trunk of the car, destined for a new area. Adult beetles would emerge from the wood during May and June and infest a new neighborhood of unsuspecting ash trees.

The natural spread of an infestation is probably no more than a half mile per year. But over the years, it is the transportation of infested firewood into new locations that continues to bring new infestations. Today the insect is commonly found in the southern half of Michigan with scattered infestations in northern Michigan, an area in Canada just east of Detroit, northwestern and several other locations in Ohio, northeastern Indiana and just north of Indianapolis, and in 2006 Illinois infestations were found in Cook and Kane counties.

"Nurseries and businesses that sell trees are monitored and controlled," said Appleby. "But all it takes is one uninformed person to transport infested firewood to bring the pests into a new area."

The beetle may have been in the Detroit area for 10 to 12 years before it was even discovered there. Shortly afterward, federal and state agencies imposed a quarantine in the infested areas, which prohibited the movement of any ash trees, logs, and firewood out of the areas. Unfortunately, prior to the quarantine, infested firewood and some infested trees were already moved to other areas. Households having fireplaces use firewood and a common practice for campers and people who own cabins in outlying areas is to take firewood to their camps and cabins. So, unknowingly infested firewood was distributed to many areas and even to adjoining states.

Appleby says that the emerald ash borer joins a long list of exotic species that have become invasive --most have been accidentally transported. "The emerald ash borer beetle is native to China, Korea, Japan, Taiwan, and parts of Russia. We can only speculate that the beetle probably arrived in the larval stage inside wood crating material from China. Shortly after arriving, adult beetles emerged from the wood and flew to local ash trees infesting them."

Although Appleby says that woodpeckers are natural predators, they feed on larger larvae but by that time the larger larvae have already done extensive damage.

From studies in the state of Michigan it is known that the insect overwinters in the larval stage under the bark of ash trees. In April the larva changes into the inactive pupal stage and then beginning in early to mid May it changes into the adult stage. The adult beetle then chews a distinctive D-shaped exit hole, about an eighth of an inch in diameter, in the bark. The adult beetle flies to ash foliage where it feeds on the edges of the leaf. After feeding for about a week, the beetles will mate. Seven to 10 days after mating the female beetle is attracted to the upper branches of a living ash tree where she deposits eggs in bark crevices. The eggs hatch in about 10 days. The larva bores into the bark and feeds just under the bark where it makes serpentine tunnels.

It is the feeding of the larval stage that is so destructive to the tree. The feeding causes a disruption in the tree's ability to transport nutrients and so as the number of tunnels continues to increase each year, the upper tree branches begin to die and kill the tree in three to five years.

To date, white, green, and black ash trees all appear to be susceptible to attack by the emerald ash borer. In some urban areas ash may comprise as much as 20 percent of their ornamental trees. "In some Michigan communities where ash lined the streets on both sides, now only stumps remain and the residents have no shade," said Appleby. "We should learn never to plant all of one tree species in a given area but plant a diversity of tree species."

Appleby said that some communities are no longer planting ash trees. "This might be a good course to take, particularly in northeastern Illinois, but in other areas it might be too drastic not to include the planting of at least some ash. Time will tell whether or not we will be successful in limiting the spread of this very destructive ash insect."

Posted by Ron Wolford at 9:15 PM | Permalink |

January 12, 2007

Illinois Department of Agriculture Expands Emerald Ash Borer Quarantine

The Illinois Department of Agriculture has expanded its emerald ash borer quarantine to include all of Kane County.

Detections of the tree-killing beetle outside the boundaries of the original quarantine prompted the expansion. The detections occurred in Hampshire, Elgin, Plato and Blackberry Townships and resulted from tree surveys to determine the extent of the Kane County beetle infestation.

"The surveys, which involved the inspection of ash trees throughout the county, were a collaborative effort of local, state and federal partners," Agriculture Director Chuck Hartke said. "While we were hoping the results would show the infestation was contained to the area where it was first discovered, the exhaustive work of survey participants will help us to develop a strategy to manage this destructive pest."

The quarantine was established after the emerald ash borer was discovered in Campton Township last June and originally encompassed 51 square miles, a territory that included the rural subdivision west of St. Charles where the beetle was first found in Illinois.

It prohibits the removal of the following items from the county:

The emerald ash borer in any living stage of development.

Ash trees of any size.

Ash limbs and branches.

Any cut, non-coniferous firewood.

Bark from ash trees and wood chips larger than one inch from ash trees.

Ash logs and lumber with either the bark or the outer one inch of sapwood, or both, attached.

Any item made from or containing the wood of the ash tree that is capable of spreading the emerald ash borer.

Any other article, product or means of conveyance determined by the Illinois Department of Agriculture to present a risk of spreading the beetle infestation.

Anyone convicted of moving prohibited items from the quarantine area without prior certification by an Illinois Department of Agriculture nursery inspector may be fined up to $500.

Forty-one trees in Kane County are confirmed to be infested with the beetle, including 31 in Campton Township. Seven of the 41 were identified through a survey method known as bark peeling. After a tree is removed, inspectors using this technique strip the bark from its trunk or branches and examine the bare wood for beetle larvae. Three infestations were detected using trap trees, a survey method where a ring of bark is removed from a tree to distress it, which makes the tree more attractive to the ash borer beetle. The rest were identified through visual inspections.

In addition to Kane County, the beetle, which has killed more than 20 million Ash trees in North America, also has been found in the Cook County communities of Wilmette, Evanston and Winnetka.

"Tree surveys are underway to determine the extent of the infestation in Cook County," Warren Goetsch, bureau chief of Environmental Programs said. "Significant progress has been made, but because the beetle was discovered there in July, a month after the detection in Kane County, the work will take longer to complete."

A beetle quarantine also is in effect in northern Cook County. Its boundaries extend north to south from the Lake County line to the northernmost city limit of Chicago and east to west from Lake Michigan to Interstate 294.

The Kane and Cook county quarantines regulate the intrastate movement of potentially contaminated wood products. The states of Illinois, Indiana, Ohio and Michigan have been placed under a federal quarantine. It prohibits the interstate movement of these same products.

How the emerald ash borer arrived in Illinois is unknown, but the department suspects it may have been transported here in contaminated firewood. To avoid the accidental introduction of the beetle to new areas, the department encourages Illinoisans to purchase only locally grown nursery stock and locally cut firewood.

Anyone who suspects a tree has been infested is urged to contact his or her county Extension office or their village forester for a consultation.

An expert panel appointed by Governor Rod R. Blagojevich has endorsed a strategy to eradicate the emerald ash borer in Kane County and prevent the destructive beetle from infesting ash trees in new areas.

After considering three containment options, the governor's Management and Science Advisory Panel recommended the removal of ash trees within approximately two square miles of the rural area east of Lily Lake where the beetle was first discovered in Illinois.

"While eradication of this pest is our ultimate goal, it may not be possible to remove every ash tree in an infested area," Warren Goetsch, acting division manager of Natural Resources for the Illinois Department of Agriculture, said. "Portions of the Kane County landscape are heavily wooded and some ash trees are simply inaccessible. Many trees that aren't susceptible to emerald ash borer would have to be cut down just to reach these trees, and even then the terrain may prevent equipment from removing them. We plan to remove as much of the ash tree population in an infested area as possible while minimizing damage to the surrounding area."

"Although the loss of trees is unfortunate, I believe that the aggressive approach we endorsed is completely appropriate," Edith Makra, panel member, arborist and Morton Arboretum Community Trees Advocate, said.

More than 2,800 ash trees are located in the area targeted for tree removal, including approximately 1,700 on private property and public rights of way. Another 1,120 are located in 60-acres of heavily forested area. About 150 ash trees currently are believed to be infested.

Before the tree cutting begins, though, the panel wants additional evidence the infestation is confined by conducting a more intensive survey to verify the infestation's so-called footprint. This survey would involve 260 ash trees – or five per square mile -- around the perimeter of the removal area, which includes the Windings subdivision. Thus far, visual inspections largely have been used to identify infested trees. However, beetle larvae can feast on a tree several years before it shows visible signs of distress, so they instructed the Illinois Department of Agriculture to perform the more reliable bark-peeling survey, which exposes the larvae if a tree is infested.

The department currently is searching for a marshaling yard to aid in the disposal of cut trees. Ideally, the site will be located within the Kane County quarantine zone, a 51-square mile area where the movement of potentially contaminated ash wood products is restricted to prevent the accidental spread of the beetle. Federal approvals also must be obtained to remove trees. The approvals are required to ensure the project does not adversely impact the habitat of any threatened or endangered species.

"The USDA is as committed as ever to help Illinois as it develops and implements plans to manage theemerald ash borer," Steve Knight, panel member and Illinois State Director for USDA APHIS PPQ, said. "Since the first report of EAB in Kane County, the USDA has collaborated with the Illinois Department of Agriculture, providing funds and resources for the training of survey personnel, establishing a USDA EAB Field Office at the Kane County Fairgrounds in St. Charles and formally entering into a cooperative agreement with the department for the efficient pass-through of federal funds for EAB management efforts."

No recommendations were made concerning Cook County because the severity of the infestation there has not been determined. A survey to identify infested trees in Kane County started June 9 after confirmation of a beetle in the Windings subdivision. A survey to identify infested trees in northern Cook County did not begun until after July 13 when the presence of the beetle was confirmed in Wilmette and was expanded after subsequent finds in Evanston and Winnetka.

The advisory panel consists of EAB experts from the Illinois Department of Agriculture, Illinois Department of Natural Resources, USDA Animal and Plant Health Inspection Service, USDA Forest Service, University of Illinois and Morton Arboretum. It is an extension of the Illinois EAB Readiness Team that prepared for the arrival of the emerald ash borer for more than two years.

In addition to a containment strategy, the panel recommended the adoption of a state statute to regulate the movement of firewood, which is the most common cause of the beetle's artificial spread. It also suggested providing advice on the use of pesticides to control emerald ash borer. Neither the USDA nor Illinois Department of Agriculture currently recommends preventative pesticide treatments.

The emerald ash borer is a small, metallic-green beetle native to Asia that has killed more than 20 million ash trees since arriving in North America in 2002. Infestations have been confirmed in five states – Michigan, Indiana, Ohio, Maryland and Illinois – as well as Ontario, Canada.

The beetle is difficult to detect, especially in newly infested trees. Signs of infestation include the presence of metallic-green beetles about half the diameter of a penny on or around ash trees, thinning and yellowing leaves, D-shaped holes in the bark of the trunk or branches and shoots growing from the base of the tree.

Anyone who suspects a tree has been infested is urged to contact their county Extension office.

Posted by Ron Wolford at 4:01 PM | Permalink |