Invasive plant war turns inward
MOSCOW, Idaho – This time of year, snow covers most of the vacant lots, neglected fields and construction sites favored by spotted knapweed. But inside a University of Idaho greenhouse, a small patch of this Eurasian invader continues to bloom with its spiky, purple flowers.
This is where George Newcombe hopes to make a breakthrough that might help turn back an ever-growing knapweed invasion. Unlike most other scientists, Newcombe isn’t focused on finding an insect or other pest from knapweed’s native range that might work in keeping the plant under control.
Newcombe, an associate professor of forest pathology and co-director of the university’s Center for Research on Invasive Species and Small Populations, believes tiny fungi that live inside knapweed could be used to control the plant. “They may be the key,” Newcombe said on a recent afternoon in the greenhouse.
These organisms, known as endophytic fungi, are found in many plant species and are the recent focus of an intense amount of research. Newcombe described endophytes as a bit like a parasite because they survive off the host plant but are usually less harmful to the plant. They are believed to boost the plant’s survival in exchange for nutrients provided by the plant.
Taxol, a cancer-fighting drug discovered in yew trees, is a compound produced by endophytes living within the tree, Newcombe said. Some endophytes make grasses poisonous to grazing animals. Others allow plants to survive in the heated soils around geysers in Yellowstone National Park.
Thanks to technological advances, researchers are beginning to understand how these fungi might help or hurt knapweed, said Cort Anderson, assistant professor at the University of Idaho and manager of the Laboratory for Ecological and Conservation Genetics.
“It’s helping us understand what gives them the advantage,” Anderson said. “It’s a very new area of investigation.”
Newcombe has since identified an endophyte that seems to be able to render knapweed sterile. The fungus typically exists in low concentrations in the plant, but when it’s cultured in a lab and sprayed in higher concentrations, it has a deadly effect. Newcombe is hoping to conduct field trials soon.
Unlike bringing in insect pests from an invasive weed’s home country, endophytic fungi don’t appear to carry the risk of unintentionally harming other plants, Newcombe said. And because the fungi are already here, this could dramatically speed the process of bringing the tool from the laboratory to mass production.
Both Newcombe and Anderson believe endophytic fungi could be key in controlling myriad invaders. Essentially, they’re a whole new category of potentially powerful weapons that barely have been explored.
By better understanding these organisms, scientists also hope to gain new clues on how invasives can be so successful against native species. One of the endophytes in knapweed, for instance, is believed to give the plant the ability to render the soil poisonous to competing native plants.
“We need to understand the basic mechanism of invasions or we’re never going to get off this treadmill,” Newcombe said.
It’s no small problem, either. The U.S. Department of Agriculture estimates invasive species cost the nation $138 billion annually. Invasive species, including pests like Eurasian water milfoil and New Zealand mudsnails, also choke waterways and rob fish and wildlife of habitat. In Idaho, the cost of invasives is estimated at $300 million a year, Newcombe said.
The problem is getting worse, with rates of invasion appearing to be speeding up, Newcombe said. Earlier this year, an invasive waterplant from South America was found growing in Moscow, Idaho. The plant, Brazilian elodea, has already choked waterways in Oregon and Western Washington, but was not thought capable of surviving here. The plant’s successful spread is blamed on everything from climate change to expanded global trade.
“When it comes to invasives, the world is becoming a very small place,” Newcombe said.
That’s part of the reason the University of Idaho launched the Center for Research on Invasive Species and Small Populations in 2004, thanks to a $1 million grant from the state’s Board of Education. One of the center’s projects is sharing research on invasives between Idaho and Costa Rica.
“When the source of the next invader could be anywhere, you have to be looking outward,” Newcombe said.