Scientists race to prevent ash tree’s extinction

DES MOINES, Iowa — Mark Widrlechner is out to save a species from extinction.

It’s the native ash tree, and although it provides $25 billion worth of timber and decorates backyards across North America, an unstoppable bug has slowly killed millions of trees in 13 states and could cause the species’ ultimate demise — unless Widrlechner is successful.

The horticulturist for the federal Agriculture Research Service in Iowa is heading an effort to collect tens of millions of ash seeds from across the U.S. that can be frozen and ready to plant when researchers figure out how to kill or control the emerald ash borer.

The process is tedious since seeds must be hand-picked from branches only in the fall. But scientists hope to avoid what happened to the American elm, chestnut and butternut trees, which were nearly wiped out by disease.

Widrlechner said the ash borer is especially devastating because it can kill very young trees and reduce the possibility that the species develop a tolerance.

“This one to me looks like it’s much more likely to lead to extinction if we don’t do anything about it,” predicted Widrlechner, who also is a professor at Iowa State University in Ames.

Ash trees are used commercially for baseball bats, kitchen cabinets and other products, and dominate the landscape in parts of the Midwest.

In Kansas and Nebraska, they account for 25 percent to 35 percent of trees and up to 60 percent in some North Dakota communities. In Iowa alone there are an estimated 88 million ash trees, state experts said.

The eastern U.S. produces nearly 114 million board feet of ash saw timber valued at $25 billion, according to the 2009 manual by the Department of Agriculture on the emerald ash borer. The potential impact on the urban landscape could include 30 million to 90 million trees and cause $20 billion to $60 billion in damage, the report estimated.

The insect is native to Asia and was first identified in the U.S. in 2002, when it was spotted in Michigan. It’s now found in Illinois, Indiana, Kentucky, Maryland, Michigan, Minnesota, Missouri, New York, Ohio, Pennsylvania, Virginia, West Virginia and Wisconsin.

The adult beetles are relatively harmless and nibble on leaves, but the larvae are deadly. They drill into trees, eat through the vascular tissue and stop the flow of water. An infested tree can die within a few years, and the emerging generation of beetles moves to other trees, Widrlechner said.

Federal and state agencies tried to limit the ash borer’s movement through quarantines, but scientists agree that there’s no way to stop the insect’s spread unless new techniques are developed.

“This pest is one like we’ve never dealt with before,” said John Bedford, pest response program manager with the Michigan Department of Agriculture. “It doesn’t seem to leave much in its wake.”

In parts of Michigan, “a majority of the ash trees are dead and gone,” he said.

Crews have collected at least 2 million seeds from stands of green, white, black, blue and pumpkin ash — only about 10 percent of the number needed to ensure the diversity of each species is represented, Widrlechner estimates.

Noel Schneeberger, an entomologist with the U.S. Forest Service, said billions of ash trees are scattered across the U.S., Mexico and Canada.

The seed collection project began in New England in 2007, then expanded to Wisconsin, Illinois and Missouri. It also includes the Forest Service, the National Resources Conservation Service, the Bureau of Land Management, the Interior Department, several state forest agencies, American Indian tribes, botanical gardens and even people with ash trees in their yards.

Ash seeds grow in clusters on branches with anywhere from a dozen to 50 seeds hanging in a group. The seeds are hand-picked in the fall and put in paper bags, then dried and sorted. Seeds shared with researchers are put in large jars and refrigerated, Widrlechner said.

Seeds in the “base collection,” which will be used to replenish the ash species, are sealed in plastic and stored in a walk-in freezer. Some remain at the North Central Regional Plant Introduction Station in Ames, and some are sent to the National Center for Genetic Resources Preservation in Fort Collins, Colo.

A similar but smaller project by the Department of Agriculture and North Carolina State University is under way for the Eastern and North Carolina hemlocks, which are threatened by the Hemlock woolly adelgid.

Large-scale seed collections were not taken before diseases nearly wiped out Dutch elms between 1930 and the mid-1970s and American chestnut trees by the 1950s. Butternut, a hardwood native to eastern North American forests, is still affected by a canker disease.

Schneeberger hopes the ash tree will avoid a similar fate. He said the problem shows that urban areas must use a variety of trees, noting that many ash trees were largely planted to replace dying elms.

“We need to pay attention to planting the right trees for the right place in urban areas and diversify the urban canopy,” Schneeberger said. “We don’t plant one street full of ash, for example, we plant a variety of species.”