Last week witnessed the return of monarch butterflies to our region and the debut of fireflies in the meadows, but the bug that grabbed our attention was the nefarious emerald ash borer (EAB). This nocent genie is officially out of the bottle as it escaped its federal quarantine zone in Prince George’s and Charles counties and surfaced in several locations in Howard county Maryland more than 30 miles away. This was particularly bad news because it confirms suspicions of many scientists that the rate of spread of EAB is now accelerating in Maryland. EAB was first detected near Detroit, Michigan in 2002, and is found in Illinois, Iowa, Indiana, Kentucky, Maryland, Missouri, Minnesota, New York, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, Wisconsin, and parts of Canada. A native of Asia, EAB likely arrived in this country in packing material. In 2003 the first EAB tremor was felt in our region when the borer was detected in a nursery in Prince George’s County. This detection confirmed the suspicions and fears of many, namely, that the EAB could be transported and relocated with infested nursery stock.
The EAB adult leaves behind a "D" shaped exit hole in the bark of the tree. This is a good clue for diagnosing the presence of this pest.
Ash trees infested with EAB were shipped in April, 2003 to a nursery in the Maryland suburbs near Washington, DC. During the spring and summer beetles moved from Michigan-grown trees to ones grown in the nursery. Some of these trees were shipped and installed in several locations in the greater Washington, DC area. Officials from the Maryland Department of Agriculture in cooperation with the USDA conducted search and destroy missions. In 2003, more than 1000 ash trees were destroyed in an attempt to eradicate this pest. State officials were optimistic about the results of the eradication program until August 21, 2006 when larvae of EAB were detected in ash trees in and near the original eradication area. What this meant was that beetles somehow escaped the first eradication attempt and established an infestation in native ash trees nearby. Sounds a bit like Jurassic Park, doesn’t it? Beetles were apparently on the loose for about four growing seasons before the beast was rediscovered in 2006. On August 22, 2006 the Maryland Department of Agriculture issued a revised Quarantine Order that prohibited anyone from moving ash trees, products, or any hardwood firewood into or out of Prince George’s County until further notice. In 2008, this rascal jumped the southern boarder of Prince George’s County and was discovered a few miles away in northern Charles County. Using historical data provided by the Maryland Department of Agriculture, we recently estimated the natural rate of spread of EAB to be just less than one mile each year. At this rate of spread, it would have taken the beast almost 30 years to move from more its introduction point in Prince George’s County to Baltimore. With the detection of EAB in Howard County, our initial projections are out the window, and our revised models put the green menace in charm city in less than 10 years.
Legless EAB larvae like these two are easily moved in firewood, logs, or branches. Please be on the lookout for these in ash tress and obey the quarantine if you live in Prince George's, Charles County, or Howard County.
Why is this news so discouraging? Here are the reasons. Ashes are among the more common native trees bordering rivers and streams in the lowland and piedmont area where they provide shade and nutrients to our riparian and woodland ecosystems. Ashes also provide food and shelter to more than 20 species of indigenous native insects. Collectively these organisms are valuable members of several ecological communities. They help the natural world go around. Ashes are also important trees in our suburbs and cities where they provide energy savings by cooling our homes and places of work, sequestering carbon, mitigating pollution, intercepting rainfall and reducing storm-water runoff, and adding aesthetic value to our landscapes and homes. As far as we know, EAB attacks all of our native species of ash and also those commonly used for ornamental purposes in landscapes. To date, it has killed more than 40 million ash trees and threatens several billion nationwide. Columbia, MD, where EAB was detected last week has a moderate population of ash trees that are now at risk. A larger concern waits just up the interstate were more than half a million ash trees grow in and around Baltimore. Their value to urban dwellers is enormous, estimated by some models to exceed $ 40 million annually. Because EAB is lethal to ashes, valuable trees will require insecticide treatments to protect them or, if they are infested and killed, they must be removed to reduce hazards to people and property. Protecting or removing more than 300,000 trees that populate Baltimore will be expensive once EAB arrives. Maryland’s cities and suburbs now face weighty decisions regarding how they will manage their valuable ash resources in the face of this egregious and lethal pest. Cities should start planning now for the almost certain arrival of this pest.
Blue Barney traps hung in trees throughout Maryland will help state officials and researchers learn where EAB is and how rapidly it is spreading.
To track the spread on this wily pest, Maryland Department of Agriculture in Cooperation with USDA has established a statewide trapping program that relies on a triangular sticky trap hung in trees. This trap is tinted the color of the affable purple dinosaur Barney and has been affectionately dubbed the “Barney” trap. For reasons known only to Mother Nature, EAB is attracted to the color purple and if beetles are in an area, they will be attracted to these traps, alight and become ensnared in sticky goo where they can be observed and recorded by Department of Agriculture workers. Thousands of Barney traps established throughout Maryland are checked from May until August to detect new infestations of EAB. An effort to manage the green menace is also underway in Maryland and other states that involve the release of tiny parasitic wasps that attack and kill EAB. To learn more about this approach, please visit the May 31, 2010 episode entitled “Parasitoids to the Rescue.” If you would like to find out what you can do to help with the Maryland’s EAB problem and its solution, please visit the Department of Agriculture’s web site at: http://www.mda.state.md.us/plants-pests/eab/ I have received phone calls from concerned citizens wanting to know if their ash trees are infested with EAB. Like a crime scene investigator you can use clues called symptoms and signs to determine if EAB is attacking your ash tree. If you click on the following link, it will take you to a web site that has my step by step guide to identifying pests attacking your ash. The page is called CSI for EAB.http://www.dnr.state.md.us/forests/forester/eab.asp If your plant identification skills are a little rusty or if you suspect that one of your ash trees is infested by EAB, please visit the Home and Garden Information Center’s EAB web page. It contains valuable links including one that will help you identify the ash trees in you landscape. Information on how to report a suspected EAB infestation is also available at this site. http://www.hgic.umd.edu/content/emeraldAshBorer.cfm
References
The interesting references “Direct and indirect effects of alien insect herbivores on ecological processes and interactions in forests of eastern North America” by K. J. K. Gandhi and D.A. Herms and “Street tree diversity in Eastern North America and its potential for tree loss to exotic pests” by M. J. Raupp, A. Buckelew Cumming, and E. C. Raupp were used in preparation of this episode. Bug of the Week thanks our friends at Maryland Department of Agriculture, University of Maryland Extension, and our Maryland Arborists that provided support, training, and the ultimate detection of the green menace in Howard County. To learn more about EAB, please visit the following web sites.
http://www.emeraldashborer.info/
http://www.na.fs.fed.us/fhp/eab/ http://pestthreats.umd.edu/content/documents/EABBulletin.pdf