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Researchers develop method to detect oak wilt earlier
Jill Odom | November 14, 2017
oak wil symptom of browning leaves

Symptoms of oak wilt result in the rapid discoloration of leaves in red oaks.
Photo: Allegan Conservation District

Oak wilt is a deadly fungal disease that all species of oak are susceptible to, but researchers at the University of Minnesota have developed a straightforward and affordable test for detection.

Too often oak wilt symptoms only appear when it is far too late. With the new technology developed by assistant professor Abdennour Abbas and his research team, oak wilt can be detected within 30 minutes and costs less than five dollars per sample.

Currently, detection of the disease is only observed with the naked eye and can only be spotted two to three weeks after infection. Laboratory techniques take from six hours to two weeks and cost $60 to $120 per sample.

“When it comes to disease detection, time is a crucial factor that decides whether lives will be saved or not,” Abbas told Phys.org. “However, making a rapid detection technology is not enough. The other challenge is to make the technology affordable and easy for people to use it.”

The process uses the agglomeration of gold nanoparticles to create a chemiluminescent signal that can be read in the presence of the oak wilt fungus DNA. It only requires dipping wood chips into a solution to extract the DNA and then mixing it with a solution of gold nanoparticles for it to be detected with a hand-held luminometer.

different types of oak wilt

The different symptoms of oak wilt in different oak species.
Photo: USDA

The team is working to create a portable system of the detection method without having to send samples to the laboratory.

Oak wilt is currently present in a majority of the eastern U.S., and in Minnesota alone more than 266,000 oak trees were infected from 2007 to 2016.

The cost of infected tree removal is estimated to be $60 million with it costing $400 to $500 per tree. This is not to mention the economic or environmental impact of losing large swaths of oak trees.

“Oak wilt is the second greatest invasive disease threat to Minnesota’s plants, second only to Dutch elm disease,” Robert Venette, director of the Minnesota Invasive Terrestrial Plants and Pests Center (MITPPC) at the University of Minnesota, told Phys.org. “The loss of elms transformed many of our urban and hardwood forests. We don’t want our oaks to be next.”

Currently there is no permanent cure for oak wilt but there are certain fungicides like propiconazole that can be used for reducing the symptoms in live oaks when applied before infection. There has been limited success with therapeutic injections during the earliest stages of infection.

Prevention is the best option when it comes to controlling oak wilt and the best practice is pruning oak trees at the proper time, as open wounds are when beetles are active resulting in new oak wilt centers.

Fungal mats are present and beetles are most active from February to the end of June. The safest time to prune is after the first hard frost, generally November through January.

According to the United States Department of Agriculture, in the North, tree paint is not necessary for wounds during the dormant season, but in other areas it is advised to be applied immediately after the tree has been wounded at any time of the year.

For more information about oak wilt, click here.

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