Ash trees could go the way of the American Chestnut

A double whammy of health problems may decimate ash trees of all species.

JEFFERSON CITY-At the end of the 19th century, forests in the eastern half of North America harbored millions of stately chestnut trees. By the close of the 20th century, the species was virtually wiped out. Foresters and arborists say the same could happen to the continent's ash trees.

The chestnut devastation was the work of a fungal disease unwittingly brought from Asia. Today a similar situation exists with ash trees and another Asian import, the emerald ash borer (Agrilus planipennis, or EAB).

This handsome, half-inch beetle's larvae tunnel under ash trees' bark, destroying their circulatory systems. Green ashes (F. pennsylvanica) seem to be the pest's preferred host, but no North American ash species is resistant. Infested trees all die. The emerald ash borer already have been found in Maryland, Michigan, Indiana and Illinois. Some of these infestations are well-established and are spreading slowly.

As if this were not bad enough, ash trees in the northeastern quarter of the United States also are in decline due to a disease known as ash yellows. It is caused by germs known as "phytoplasmas." Like the EAB, the ash yellows organism damages trees' inner bark, interfering with transport of water and nutrients. Forest health experts suspect that insects spread the disease. Green ash and white ash (F. americana) are the species most often affected.

Adverse conditions, such as the droughts that have plagued parts of Missouri in recent years, make ash trees more susceptible to both afflictions.

Since arriving in North America, the EAB has killed more than 20 million ash trees and caused economic losses running into the tens of millions of dollars. Rob Lawrence, a forest entomologist with the Missouri Department of Conservation, said the pest could be equally devastating in Missouri, where green and white ash trees are important components of native forests. He noted that ash trees are even more prevalent in urban areas, where their straight trunks and vigorous growth has made them popular park and residential landscape trees. "This beetle has the potential to devastate both rural and community forests," said Lawrence.

Ash wood is hard, tough and straight-grained, which makes it good material for bows, tool handles, baseball bats and musical instruments. Ash trees account for 3 to 10 percent of trees in natural woods in Missouri and as much as 30 percent of urban trees.

Ash trees are important ecologically, too. Mature ash trees often develop cavities that certain bird species need for nesting. Their seeds provide food for cardinals, finches and other birds, and their presence lends diversity to Missouri forests, making them less vulnerable to devastation by diseases or parasites.

"This insect has the potential to remove the ash component entirely from our forests," said Lawrence, "something similar to how chestnut blight removed large chestnut trees from Eastern forests, and potentially worse than what Dutch elm disease has done to elms. This is not a part of normal forest ecology. This is a non-native insect killing trees that have previously never been exposed to this insect and have no resistance to it."

Lawrence said the loss of ash trees in urban areas would have a huge economic impact. Dead trees quickly become safety hazards if left standing, and the cost of tree removal is high.

The Conservation Department works with the Missouri Department of Agriculture and the USDA Forest Service to conduct EAB surveillance. The agencies are checking areas considered to be at high risk for infestation. These include campgrounds, parks and areas where large numbers of ash trees have been planted since the mid-1990s. Last year, state and federal agencies surveyed 69 campgrounds, recreation areas and urban areas. They also are monitoring nurseries where trees are raised. So far, no EABs have been found here.

Citizens have a role to play in keeping the EAB out of Missouri. When EABs go state-hopping, it is almost always in firewood or nursery stock. Nursery owners and agriculture officials are taking measures to keep the beetles out of nurseries. That leaves firewood as a source of infestation.

Missourians need to be aware of the danger of bringing infested firewood into the state. The best way to do this is not to bring firewood home from other states. If you accidentally bring firewood into Missouri, burn it immediately.

Missourians also can help by being alert to telltale signs of EAB infestations and reporting them immediately so state officials can contain them.

EAB larvae create S-shaped trails under infested trees' bark. Early symptoms of damage in living trees include dead branches in the crown, and the sprouting of many small branches on the trunk. When the adults emerge through the bark, they leave D-shaped holes up to three-sixteenths inch in diameter. Other wood-boring insects leave oval or round holes of various sizes.

Lawrence noted that Missouri has a number of native beetles that are metallic green, and ashes can suffer from many other conditions that cause them to die. If you think you may have EABs, check conclusive evidence, such as the S-shaped burrows and D-shaped exit holes, before calling authorities. If you do see signs of EAB, contact the nearest Conservation Department office.

For more information about EAB, visit:

-Jim Low-