By Mark Shour
Iowa State University
Iowa State University (ISU) Extension is starting its third year of a collaborative effort to survey the state of Iowa for a destructive, exotic insect pest. The emerald ash borer, Agrilus planipennis, was first discovered in Detroit, Mich., in 2002, and has killed more than 15 million ash trees in Michigan.
Scientists estimate that emerald ash borer has been in the United States for 10 to15 years, quietly acclimating to its new home and building up populations. Pockets of damaging activity for this exotic beetle have also been found in Indiana, Ohio and Windsor, Ontario, Canada. Cost to affected municipalities, property owners, plant nurseries and forest products industries are in the tens of millions of dollars.
Other collaborators in this project include the Iowa Department of Natural Resources (IDNR) – Forestry Bureau, the Iowa Department of Agriculture and Land Stewardship – State Entomologist Office, the United States Department of Agriculture – Forest Service and the USDA – Plant Protection Quarantine division.
2005 Survey Results
During the summer of 2005, visual surveys were conducted in each of Iowa’s 99 counties. More than 1,300 ash trees in 238 sites (cities, towns, near sawmills or other wood products industries and in various recreational areas) were observed for the signs and symptoms of emerald ash borer activity. Although several instances of native boring insects were recorded, emerald ash borer was not found.
Also in 2005, sentinel/“trap” trees were established at 12 sites across central and eastern Iowa before Memorial Day. Approximately half of these were 2-inch caliper green or white ash trees in containers. They were planted in campgrounds where natural stands of ash trees were limited. The trees were removed from their plastic pots and put in the ground, but in a shallow hole to mimic drought stress. Other trap trees were created by double girdling ash trees (4 to 13 inches diameter) where native ash stands were plentiful. Because sex pheromones (perfume) are not known for the emerald ash borer, an intentionally stressed tree is thought to be more attractive to insect borers.
During October 2005, the 48 sentinel trees were cut down, bark peeled following the USDA Forest Service protocol for this insect, and any borer larvae were preserved. Approximately two-thirds of the trap trees displayed evidence of destructive insect activity. Fortunately, only native borers were found. The insect species found included the redheaded ash borer, the ash/lilac borer, two types of bark beetles and a native flatheaded borer.
2006 Efforts Planned
The plan for 2006 includes revisiting sawmills and wood product sites, but the emphasis will be conducting visual surveys in federal, state and county campgrounds in Iowa. Trap trees will again be established, but sites will extend across the state, following major highways and campgrounds. These areas are considered the highest risk sites in the state because the emerald ash borer moves long distance in firewood.
Concern about interstate movement of firewood into Iowa was confirmed this past summer. Campers bringing firewood from Michigan, Indiana and Ohio were observed at a federal campground in Iowa; the park managers exchanged the firewood for local wood. Five bundles of the exchanged firewood from the aforementioned states were examined and, fortunately, emerald ash borer was not found.
How You Can Help
There are several things you can do to assist in looking for the emerald ash borer in Iowa.
- Know the signs and symptoms of emerald ash borer activity.
- Emerald ash borer adults are dark, metallic and emerald green beetles, measuring one-half inch long and one-sixteenth of an inch wide.
- White larvae feed under the bark of ash trees and produce “S-shaped” tunnels.
- Adults leave “D-shaped” emergence holes on ash tree trunks. Native borers leave round or oval holes.
- Symptomatic trees display thinning and dieback of the upper one-third of the crown. Root and stem suckers (“water sprouts” or epicormic shoots) are produced by affected ash trees directly below borer activity.
- A photographic gallery for the emerald ash borer can be found at www.insectimages.org
- Obtain an emerald ash borer poster and post it on a bulletin board in your workplace. Posters as well as wallet-size cards are available through Iowa Department of Natural Resources – Forestry Bureau and Iowa Department of Agriculture & Land Stewardship – State Entomologist Office.
- Bookmark your Web browser and keep up with current research and survey findings in Michigan, Indiana and Ohio: http://www.emeraldashborer.info/
- Report suspected sightings of emerald ash borer adults or symptomatic trees to the State Entomologist’s office, any local ISU Extension county office or any district forester with the IDNR. Remember, there are native insect borers that colonize declining or dying ash trees and are not of special concern.