“Going, going, gone! Big Papi does it again with a walk-off home run for the Red Sox!”
How many times have Sox fans heard this call after that tell-tale crack of bat on ball? Until recently, the wooden bat that struck that ball would have been made of ash from the Northeast. (Some players now use maple, too.) Red Sox third baseman Mike Lowell loves the sound of ash striking a baseball. He has said that he can instantly tell by the sound of the ball hitting the bat if a player is using maple or ash. But if the emerald ash borer has its way, all ballplayers might soon be swinging maple, or something other than ash.
The emerald ash borer (EAB) is a small beetle (it easily fits on a penny) discovered in 2002 in Michigan and Windsor, Ontario. The insect kills North American ash trees, those in the genus Fraxinus. This includes green, white, and black ash, all native to Vermont and New Hampshire. The larvae create tunnels called galleries just below the bark in the phloem layer of the tree. These galleries stop water and nutrients from being transported up the tree. Branches begin to die first, and finally the entire tree goes. Large trees may die within three to four years of initial infestation, and saplings or small trees may die after just a single year.
The emerald ash borer is an exotic accidentally introduced from the Far East. It probably arrived in Detroit stowed away in a wooden pallet from China, perhaps as long ago as the late 1980s or early 1990s. With worldwide trade occurring at the highest rate in human history, it is not surprising that exotic pests are also arriving at records rates. The economic and ecological troubles they cause are enormous.
Over 50 million ash trees have been killed in the United States since EAB was discovered. In just the first two years after discovery, the United States Department of Agriculture spent nearly $50 million on eradication. Ohio estimates it has 2.1 billion board feet of ash exposed to EAB in its forests, worth almost $1 billion at the sawmill.
New England is free of EAB for now. Since its original detection in Michigan and Ontario, the beetle has been found in Ohio in 2003, northern Indiana in 2004, northern Illinois and Maryland in 2006, and in western Pennsylvania and West Virginia in 2007.
The emerald ash borer spreads in North America through a combination of local range extension, associated with local flights by adult beetles of up to a half-mile, and by long-distance “jump dispersal,” caused by human movement of infested saplings or contaminated firewood. The borers arrived in Maryland when a nursery imported ash saplings from Michigan despite a quarantine.
The initial discovery of EAB and its subsequent identification took several months. Little was known about this relatively obscure Asian insect at the time. In the Asian scientific literature, there were species descriptions and only two brief accounts with general information about its biology in China.
Recent research shows that the beetle can have a one- or two-year life cycle. Adults begin emerging in mid- to late May, with peak emergence in late June. Females usually begin laying eggs about two weeks after emergence. Eggs hatch in one to two weeks, and the tiny larvae bore through the bark and into the cambium – the area between the bark and wood where nutrient levels are high. The larvae feed under the bark for several weeks, usually from late July or early August through October. They typically pass through four stages, reaching a size of roughly an inch long. Most EAB larvae over-winter in a small chamber in the outer bark or in the outer inch of wood. Pupation occurs in spring, and the new generation of adults will emerge in May or early June to continue the life cycle.
Quick identification of infestation areas is key to halting the EAB’s spread. Adult beetles leave distinctive D-shaped exit holes in the outer bark of the branches and the trunk. Adults are roughly a half-inch long with metallic-green wing covers and a coppery red or purple abdomen. They may be present from late May through early September but are most common in June and July. Signs of infestation include tree canopy dieback and yellowing or browning of leaves, by which time there are hundreds of beetles that have already reproduced.
State and federal agencies are trying to stop EAB through education, identification of infestations, quarantines, and eradication, though the prognosis is not good. If we can all help keep EAB out of New England, the only thing “going, going, gone” will be another Red Sox home run, not our valuable ash trees.
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