Oregon burns trees to save them

With a quick response, they were able to keep it restricted to the “generally endemic area,” an 89-square-mile plot where sudden death of oak trees is common. No one is permitted to transport Tanuak in or out of this area. Trunks of coniferous trees coming from the infested area should be cleaned of all debris and soil. government reports I predicted that if the infested area spreads, Asian markets could sanction exported Oregon lumber. Officials regularly monitor Oregon nurseries for Phytophthora ramorum. Until Peterson’s discovery in April, the pathogen was believed to have been successfully contained.

Photo: Oregon Department of Forestry

Peterson’s discovery was more than 20 miles from the quarantine border, too far for spores to travel alone. Analysis of the samples confirmed that the trees were infected with Phytophthora ramorum, but that wasn’t the only bad news: it was a new species of the pathogen, “North American Two,” or “NA2” (named after the continent on which it was first isolated in the laboratory), which was previously only discovered in nurseries. This means that it was a new introduction – likely also from an imported nursery, although it has not been confirmed – and an unexpected new version of the organism.

For Peterson, this was shocking, and most of all disappointing. “The nursery industry, in particular, has invested a lot of energy in monitoring Phytophthora ramorum, and trying to prevent the spread of these outbreaks,” she says. But plant pathogens, like human viruses, are small, cunning and difficult to defend. The disease “lives in the soil, and there’s a lot of movement of plant and soil material from one site to another, and that kind of thing happens,” Peterson says. “It’s no surprise that this eventually happened.”

No one yet knows how NA2 will behave in the woods, although in some laboratory studies it appears to be more aggressive than NA1, the strain now prevalent. In a worst-case scenario, a more contagious strain could spread beyond the tanuak to other species, perhaps even Douglas Fir and other trees of commercial importance.

Dealing with this new battle front fell largely on the shoulders of Sarah Navarro, a Sudden Death Oak pathologist. She and her team surveyed the affected area, and found that more than 146 of the 186 wild tanhuaks and rhododendrons they took tested positive. The incidence of NA2 was much greater than they originally thought.

They could have tried to clean up the tanoaks and then compost them, but this is a slow and complex process that leaves behind piles of logs that could be confused with firewood, creating opportunities for unintentional campers to accidentally move infected logs. Navarro felt she had only one real choice: cut and burn. “This is not the business I got into,” Navarro says. But it is the best tool they should try to slow its spread.

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