Sudden oak death, which wreaked havoc through California forests, was preventable, a new research has revealed.

A water mold pathogen caused by Phytophtora ramorum resulted in sudden oak death that downed millions of trees covering hundreds of square miles of California forests. The disease was first observed in 1995 when it tore through northern California and killed iconic tanoak and oak forests. By 2002, the pathogenic strain affecting shrubs was noted in the Southwest of England.

Using mathematical models, University of Cambridge researchers found that if control was immediately implemented as early as 2002, the disease could have been slowed down and its ecological impacts could have been reduced. Unfortunately, the sudden oak death and its effects could neither be prevented nor slowed down today.

At present, treatment of the disease could only be achieved by cutting down the infected trees. Opting for chemical treatment may prove to be impractical and expensive at this point because the disease covers large areas already.

Lead author Nik Cunniffe from the Department of Plant Sciences at the University of Cambridge said that successful control of the epidemic today would not be possible even if huge monetary investments are spent on control measures. What could be done right now is to compare potential strategies and start cutting down the trees to salvage remaining healthy trees.

"Our model showed that, with a very high level of investment starting in 2002, the disease could not have been eradicated, but its spread could have been slowed and the area affected greatly reduced," said Cunniffe.

The researchers are presently working with the Department for Environment, Food & Rural Affairs and the Forestry Commission to plan out management strategies on how future epidemics can be effectively controlled by predicting how the disease would spread.

Senior author Chris Gilligan, who is also a member of the Department of Plant Sciences, said the epidemic will inevitably happen again. More sites would be affected and this is where their tool would prove to be effective - by identifying how, when, and where the disease would progress.

Their models, Gilligan said, consider the ecological system's response along with budget changes. With this, it would be easier to investigate success and failure rates of different strategies in varying areas after an epidemic.

Cutting down trees is not the solution because more susceptible vegetation would simply sprout back and become infected once again, explained Cunniffe.

Effective control of the disease before it becomes an epidemic is very crucial in maintaining the ecosystem's biodiversity. Now, numerous deaths of trees are already increasing the risk of California fires due to drying fallen trees. Epidemic like this can indeed happen again, particularly since a large number of microbial species are yet to be discovered.

The study was published in PNAS on May 2.

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