IOWA STATE (US)—In a race against time and nature, a modern-day Johnny Appleseed is working to defend ash trees from the devastating effects of the emerald ash borer.
“Where these borers have been present the longest, it has basically been a total wipeout,” says Mark Widrlechner, assistant professor of agronomy and horticulture at Iowa State University.
“That is something we rarely see in nature,” Widrlechner says. “It’s uncommon for a pest to come in and just clean something out. It doesn’t just attack sick trees. Emerald ash borer attacks healthy trees. It attacks small trees. So you don’t have just big, old trees falling to this, you’ve got 2 to 3 inch saplings falling to this.”
Widrlechner is a horticulturist for the United States Department of Agriculture’s Agricultural Research Service and a curator at the North Central Regional Plant Introduction Station in Ames, Iowa, which is responsible for collecting and maintaining ash and other seeds for the USDA’s National Plant Germplasm System.
Native to Asia, the emerald ash borer’s larvae burrow just under the bark and into the circulatory system of the tree. The larvae interrupt the tree’s water and nutrient delivery system. Starved of nutrients, the branches die. Eventually the entire tree is lost.
Estimates from New York State, one of the states researchers predict the insect will infest as it spreads outward from Michigan, where it was first discovered in 2002, put the total number of ash trees destroyed at 70 million.
Widrlechner is collecting seeds from different ash species including green, white, blue, and black ash, and many variations within each species. He thinks he may be about 10 percent there.
“When I first found out about the emerald ash borer, we had about 60 different types of ash tree germplasm (seed) in our system,” he says. “Now we have about 220. Ultimately, I think we’ll need at least a couple thousand to represent the diversity that’s out there. In the next two years, we should really start to make a dent in it.”
Widrlechner is the national coordinator for all the agencies involved with seed collection and conservation, which include members of the ARS, the United States Forest Service, the Animal and Plant Health Inspection Service, the Natural Resources Conservation Service, the Bureau of Land Management and state agencies and public gardens.
“We’ve got a lot of people working on it,” he says. “I just got back from southern Wisconsin and northern Illinois looking for good, natural populations that have seed. We find them, mark them with the GPS coordinates, and then go back when the seeds are ready in September and October.”
One of the problems this year is that many of the trees are not producing very many or very good quality seeds, something that happens in certain years for unknown reasons, Widrlechner says.
“The strategy that we’re following right now is focused on the area just outside the range of the insect or the area where the insect is just moving into,” he explains. “Places where the insect has been for a while we’ve lost. There’s just so little ash to go back to.”
Once the seeds are collected, they are stored in the Plant Introduction Station and also at a secure backup site at the National Center for Genetic Resources Preservation in Fort Collins, Co.
The Plant Introduction Station is a joint project of Iowa State University, the USDA, and the State Agricultural Experiment Stations of the 12 north central states as part of the National Plant Germplasm System. The facility keeps an inventory of many types of plant germplasm. The seeds are used in research locally and sent to researchers around the world as needed.
The effect of losing the nation’s ash trees would be felt in many areas, most notably in the ecosystem, Widrlechner says.
“I’m really concerned,” he explains. “You take a major tree out of the forest and what is going to fill the hole? Another native tree might do it or something non-native could fill the gap and change the ecosystem.”
Despite the challenges, Widrlechner says there are reasons for long-term optimism, because ash seeds tend to remain viable even after years of cold storage. If, and when, the germplasm in the Plant Introduction Station is needed, new ash trees should grow from the stored seeds.
Iowa State University news: www.news.iastate.edu