Editor’s Note: This article first appeared in Delta Wildlife, Volume XXII, No. 4, Winter 2014, pages 34-35.
The Emerald Ash Borer (Agrilus planipennis), or EAB, is a metallic green, 1/2-long by 1/8-inch-wide, wood boring beetle native to Asia. The EAB attacks all species of ash (in the genus Fraxinus) in North America, four of which grow in Mississippi. It also attacks other woody species in the same plant family such as fringe tree, which is often planted as an ornamental. The borer is believed to have been introduced to North America in the 1990s. In July 2002 it was found in and around Detroit, Michigan and Windsor, Ontario, Canada. Since then the insect has steadily spread to the south, west and east and now resides in two Canadian Provinces and twenty-four States, including Arkansas, Tennessee, and Georgia. Detection surveys will likely identify the EAB in more states before long.
Adult beetles are active in spring and summer when females lay eggs on the bark along the trunk and lower portions of major branches. The larvae burrow through the bark where they feed on the tree’s water- and nutrient-conducting tissues during the summer and early fall. Larval galleries are typically S-shaped (serpentine) and increase in width as the larvae grow. One female can lay up to 90 eggs, which in heavy infestations, and over time, can lead to severe damage to a tree’s ability to transport water and nutrients thereby leading to a decline in the tree’s health. An EAB infestation usually kills the ash host within 2-5 years. Adult beetles chew their way out of the tree leaving telltale D-shaped emergence holes that are about 1/8th inch wide.
In July 2014, Arkansas became the twenty-fourth state to detect and confirm the presence of the Emerald Ash Borer. Currently, there are six counties in south central Arkansas confirmed to have the borer. These six along with nineteen surrounding counties comprise an Arkansas State Plant Board EAB quarantine area. Non-native pests (insects, pathogens, and plants) are often spread by people transporting items that they do not realize contain the pests and this is probably how the Emerald Ash Borer moved so quickly from the Detroit area throughout the eastern US in little more than a decade. For that reason, the quarantine in south central Arkansas includes not only the insect itself, but also nursery stock, green lumber, and all other living and dead material of the genus Fraxinus and all hardwood (non-coniferous) firewood.
It is a matter of some concern that this pest is now within 150 miles, or less, of our large, ash-rich bottomland hardwood forests such as the Delta National Forest, White River National Wildlife Refuge and thousands of acres of privately owned timber and hunting land. Ash species comprise about 2 to 3 percent of all live trees in Arkansas, Louisiana, and Mississippi but most ash volume occurs in bottomland hardwood forest types. Presently, there are no practical means of controlling the spread of this insect that is considered by some to be the most destructive forest pest ever seen in North America and for which the scope of the damage could reach billions of dollars nationwide if not stopped. Several universities and the U.S. Forest Service are studying the biology of the EAB, its rate of spread, EAB detection methods, several insect predators that attack EAB, and the efficacy of insecticides in protecting trees in infested areas. While ash trees in urban areas, yards, and parks can be replaced with other species not attacked by the EAB, the replacement of ash species in natural forests following widespread mortality likely will be determined by the composition of the remaining tree species in the stand as dictated by site and the extent of the disturbance caused by the EAB.
For those interested in learning more about the Emerald Ash Borer there are several informative websites available. The following website maintained by the USDA Forest Service and Michigan State University may be the most comprehensive available in that it involves Canada and all the US states in which the EAB occurs. (http://www.emeraldashborer.info/index.cfm#sthash.xhobB0Jp.dpbs)
In addition, the Southern Hardwood Forest Research Group, affiliated with the US Forest Service, Southern Hardwoods Lab in Stoneville, MS, will address the EAB during its annual meeting in Stoneville on February 19, 2015. One speaker with the US Forest Service in Minnesota will review the history of the EAB in the US and a second speaker with the Arkansas Forestry Commission will update the group on the status of the insect in that state. For more information on the SHFRG meeting please contact Mrs. Penny Byler at firstname.lastname@example.org or (662)-686-3154.
Ted Leininger is a Research Plant Pathologist and the Project Leader of the USDA Forest Service, Center for Bottomland Hardwoods Research headquartered in Stoneville, Miss.