PATTERSON, Mo (MDC) - State and federal agencies are launching new efforts to discover whether emerald ash borers have spread beyond the infestation discovered in Missouri last year, and they are asking for citizens' help in containing the outbreak.
Missouri joined nine other states with known emerald ash borer populations last July, with the discovery of an infestation in Wayne County. That infestation, believed to be at least five years old, has spread at least a mile from the original site at the Greenville Recreation Area at Lake Wappapello.
Federal and state officials say transporting firewood from place to place poses the biggest risk of spreading the destructive pest. They say citizens can dramatically reduce the risk from emerald ash borers by burning all firewood where it is obtained. The challenge is slightly different for the government agencies responsible for forest health.
"A big part of the challenge of preventing this pest's spread is knowing where it is," said Missouri Department of Conservation Forest Entomologist Rob Lawrence. "We could have other infestations in Missouri, and emerald ash borers could exist undetected in other states."
Lawrence said that uncertainty makes caution imperative. She said government agencies' greatest challenge is raising public awareness of how devastating emerald ash borers can be and how they spread.
The emerald ash borer is an Asian beetle that appears to have gained its first North American foothold in southern Michigan in the early 1990s. The most likely source of that infestation was wooden packing materials. Since then the emerald ash borer is estimated to have killed more than 50 million ash trees in rural forests and city landscape plantings from Virginia and Missouri north into Canada.
Most trees die three to five years after being attacked. The cause of death is damage to tissue beneath trees' bark. This tissue carries water and nutrients between tree leaves and roots.
Adult emerald ash borers are weak fliers. Without outside help, infestations spread very slowly - one-half to two miles per year. However, the borers spend much of their lives tunneling beneath bark, and this has been the key to the pest's rapid spread.
"Moving one piece of firewood from an infested area can result in an outbreak in a completely new area hundreds of miles away," said Lawrence. "Because this insect spends most of its life cycle hidden inside trees, infestations are difficult to detect until they are well-established. In the meantime, newly infested areas can be the source of other outbreaks if campers, hunters or firewood suppliers transport wood to other areas."
Lawrence said Missouri needs to determine the extent of its emerald ash borer problem in order to combat it most effectively. To do that, the Conservation Department, the Missouri Departments of Agriculture and Natural Resources, the University of Missouri, the U.S. Army Corps of Engineers, the U.S. Department of Agriculture Animal and Plant Health Inspection Service (APHIS) and the USDA Forest Service are conducting several emerald ash borer surveillance efforts.
Two surveys involve large plastic traps whose color has been described as "Barney purple," a reference to the dinosaur of children's television fame. The traps are triangular in profile and measure approximately 1 foot by 2.5 feet. The purple traps are highly visible to people, but more important the color attracts adult emerald ash borers.
To make the traps even more effective, they are baited with an artificial attractant that mimics chemicals produced by stressed ash trees. Emerald ash borers sense these chemicals, which betray stressed trees that are particularly susceptible to parasites. Insects that land on the traps are caught in sticky material.
Approximately 1,000 of the traps will be placed this month within an 8-mile radius of the Corps of Engineers' Greenville Recreation Area. In addition to this "delimiting" survey, participating agencies are placing 250 to 300 traps at approximately 50 high-risk sites around the state. These sites include campgrounds, sawmills and tree nurseries.
When the traps are retrieved and examined in July and August they will reveal how far Missouri's first known emerald ash borer infestation has spread.
Another technique for detecting emerald ash borers is creating "detection trees." This involves selecting ash trees in target areas and "girdling" them - cutting through their bark all the way around the trunk with a chainsaw. Detection trees produce a chemical signature like the attractant used in traps. Periodic checks of sentinel trees reveal whether emerald ash borers are nearby. This technique is being used in the area 5 miles north and south of the Greenville Recreation Area.
Entrenched emerald ash borer infestations like the one in Wayne County are nearly impossible to eradicate. Instead, state and federal officials are focused on containing the outbreak and slowing its spread. The Corps of Engineers is cutting down and burning affected ash trees, and APHIS and the Missouri Department of Agriculture have imposed a quarantine, prohibiting the movement of wood products or nursery stock out of the county unless a business first signs a compliance agreement to ensure that materials leaving the area are borer-free.
"We are not trying to shut down the forest products industry," said APHIS Pest Survey Specialist Christopher Pierce. "We are working with them to ensure they can keep operating. If you work with any type of wood products and you are concerned about your business, contact us and we will find a way to maintain your business."
So far, no ash trees have been found resistant to the emerald ash borer, so the implications of the infestation are severe. Even before the emerald ash borer reached Missouri, ash trees here were suffering from "ash yellows" disease and a complex of insect and disease problems called "ash decline." Forestry officials say these problems combined could produce devastation unlike any seen since chestnut blight all but exterminated the American chestnut from forests in eastern North America.
Pierce said the public has a critical role to play in preventing the spread of emerald ash borers. He said the most important thing for citizens to understand is not to move firewood around.
"The risk from moving firewood dwarfs all the other means of spread," Pierce said. "Because there could be infestations that we don't know about yet, you could spread borers by taking firewood just a few miles. The only way to be sure you don't accidentally spread this pest is to buy or cut firewood where you want to use it and burn it all there."
Ash trees around homes or businesses should be checked for signs of emerald ash borer infestation if they show signs of stress. Signs include splits in the bark running up and down the tree trunk and D-shaped exit holes measuring approximately 1/8-inch in the sides of trees. Other wood-boring insects leave oval or round holes of various sizes. The borers' larvae create S-shaped trails under infested trees' bark.
Early symptoms of emerald ash borer damage in living trees include dead branches in the crown, and the sprouting of many small branches on the trunk.
Missouri has a number of native beetles that are metallic green, and ash trees can suffer from many other conditions that cause them to die. If you think you may have emerald ash borers, check for other specific evidence, such as the S-shaped burrows and D-shaped exit holes, before reporting them.