OARDC, OSU Extension Join Effort to Fight Ash Pest Found in Ohio

March 5, 2003

WOOSTER, Ohio — Scientists with the Ohio Agricultural Research and Development Center (OARDC) and Ohio State University Extension are joining a statewide effort to control the spread of a dangerous exotic pest of ash whose presence was confirmed in Ohio Feb. 28. Larvae collected early February from a residence in Whitehouse, near Toledo in Lucas County, was positively identified last week by the U.S. Forest Service (USFS) as emerald ash borer (EAB), Agrilus planipennis —a beetle native of Asia discovered for the first time in the United States June, 2002 in Michigan’s Detroit area. “This pest could have the same devastating effect as chestnut blight and Dutch elm disease, which pretty much eliminated native chestnuts and elms from Ohio forests,” said OARDC entomologist Dan Herms. “It can also have a big impact on the nursery industry, since any ash big enough to hold an insect (one-inch-caliper trees) can be attacked by the borer.” Herms and OSU Extension entomologist David Shetlar will be part of the Ohio Emerald Ash Borer Task Force, a group of experts and officials established by the Ohio Department of Agriculture (ODA) upon confirmation of the pest in Buckeye territory.  The task force —which will meet March 13 to evaluate the situation and determine a course of action— also includes representatives from ODA, USFS and the Ohio Department of Natural Resources (ODNR). “We will discuss potential approaches to deal with this problem,” Herms said. “We will also review Michigan’s EAB plan and see if we want to join with them in this effort.” Six counties in southeast Michigan —Livingston, Macomb, Monroe, Oakland, Washtenaw and Wayne— and neighboring Essex County in Ontario, Canada, have confirmed EAB populations. The Michigan Department of Agriculture (MDA) has enacted a quarantine that restricts movement of ash logs and other untreated ash materials outside of the infested area to prevent further spread. Ohio could issue a similar quarantine for Lucas County, but no such action will be taken until the affected area is surveyed to determine the extent of the problem, ODA indicated in a press release. The beetle Because of its recent discovery in North America, little is known about the emerald ash borer’s behavior. U.S. Department of Agriculture (USDA) researchers speculate the insect was brought to the United States via infested wooden shipping crates and has been established in the Detroit area for at least five years. EAB belongs to a group of insects known as metallic wood-boring beetles. Adults are dark metallic green, half inch long and one-sixteenth of an inch wide. Larvae are creamy white, flat, slender and reach 1 to 1 1/4 inches in length when mature. “This beetle seems to be behaving very similarly to other insects in the genus Agrilus, such as the bronze birch borer,” Herms explained. “But unlike other wood boring insects, which only target weakened trees, the ash borer also attacks healthy ones. This is alarming because ash trees are common both in natural forests and landscapes throughout Ohio and the eastern United States.” Like the bronze birch borer, EAB often infests trees during two to three years, causing them to gradually decline and eventually die. But heavy infestation, Herms pointed out, can kill a tree in one season. “Damage is done by the larvae, which feeds on the phloem tissue or inner bark layer of the three,” he said. “This disrupts the flow of nutrients from the canopy to the roots, after which the tree dies.” Adult emerald ash borers emerge in mid-May and are active until July, flying around the tree and feeding on foliage. Flight dispersal is generally reported to be local, not more than 26-39 feet in distance and under 6 feet in height. Adults lay eggs on the bark surface, inside cracks and crevices, from early June to late July. Larvae actively feed from mid-June to mid-October. The borers overwinter as fully grown larvae in pupal cells constructed in the outer sapwood or in the bark. These larvae pupate the following spring, and the cycle starts again. There is only one generation per year. Common signs of infestation include thinning of the crown and crown dieback; appearance of epicormic branches, or unusual sprouts, along the main trunk and on major branches; longitudinal bark splits two to four inches long; frass-filled, zigzagging larval galleries about one-fourth of an inch wide under the bark; presence of small woodpeckers that eat the larvae during the winter; and D-shaped emergence holes on the bark about one-eight of an inch wide. “The D-shaped exit holes are very characteristic of emerald ash borer,” Herms said. “Native borers that prey on ash to a lesser degree make circular exit holes, about one-quarter of an inch wide. Unlike emerald ash borer, they feed on the sapwood and expel sawdust from the tree.” Impact Thus far, EAB has been found in all native species of ash present in the affected area —white, green and black. Herms speculates that blue ash, which grows in the lime-rich soils of southwestern Ohio, will also be vulnerable to the beetle if it ever gets there. Ash is one of the most common Ohio trees, present in every forest type of the state, said Dan Balser, forest health administrator with ODNR’s Division of Forestry. According to the most recent forestry survey (1991), there are 3.8 billion white ash trees in Ohio, covering 850,000 acres of the state’s 8 million acres of woodlands. White ash is one of the primary commercial hardwoods in the United States, used, among other things, for flooring, cabinets and baseball bats. According to Andy Sabula, Division of Forestry’s program administrator for forest industries, the market for ash in Ohio is centered around the manufacturing of tool handles. “Ohio has two major tool handle plants, Ames/True Temper in Noble County and Crook Miller Co. in Defiance,” Sabula indicated. “The state has approximately 2.1 billion board feet of ash saw timber that is worth almost $1 billion at the sawmill. If the EAB infestation is substantial enough to warrant salvage cutting, the prices paid for ash logs are sure to be negatively impacted.” Ohio nursery and landscaping industries would also suffer if the emerald ash borer infestation gets out of control. According to USDA’s 1998 Census of Horticultural Specialties, Ohio is one of the top ash producers in the country —27,000 trees with a total value of $2.3 million a year. In Michigan, another top grower of ash for landscape purposes, EAB will cost green industry firms within the infested area an estimated $8 million, according to a Michigan Nursery and Landscape Association survey. The pest is forcing growers to destroy all ash inventories, and landscapers have to replace trees to fulfill guarantees. Emerald ash borer has killed or is killing as many as five million trees in Michigan, MDA reported.  Management and prevention There is no practical insecticide treatment that will destroy this pest. Michigan State University entomologists recommend applying imidacloprid (Merit 75 WP) to infested trees that are not more than 50 percent dead. Insecticides will not help heavily infested trees, Herms noted, because the severed phloem tissue is not be able to transport the chemicals throughout the tree. “Borers are difficult to manage because they hide under the bark, taking advantage of the tree’s natural protection,” he said. “They are hard to see and it’s also hard to apply insecticides to control them.” ODA is asking citizens to watch out for the beetles and report any signs of infestation to their local OSU Extension office or to the Division of Plant Industry by calling (800) 282-1955.  People should refrain from moving ash trees, lumber or firewood inside or beyond the borders of Lucas County. Also, if you receive such items from Lucas County, please notify ODA at the above-mentioned telephone number. For more information on EAB, log on to http://www.na.fs.fed.us/spfo/eab/. OARDC and OSU Extension are part of Ohio State’s College of Food, Agricultural, and Environmental Sciences.

Author(s): 
Mauricio Espinoza
Source(s): 
Dan Herms