Heating Kills Greening
Posted on: Sunday, December 08, 2013
Monday's party/meeting will be at Palma Sola Botanical Park at 7 PM
Writing for Florida Grower Magazine (http://www.growingproduce.com/citrus/researchers-look-to-the-sun-for-help-in-citrus-greening-fight/), Frank Giles tells of yet another effort at USDA's Horticultural Lab in Fort Pierce to dampen the horrendous impact of Citrus Greening (HLB) on Florida's Citrus industry. The search for an actual cure goes on, but the article describes another technique to keep trees productive after infection with the disease. This one relies on thermotherapy, the exposure of trees to high temperature. Thermotherapy has been used to help other diseases, and Dr. Yong-Ping Duan, pathologist, decided to look at the value of it against HLB.
The first testing exposed potted plants under nursery conditions to temperatures of about 104 degrees F by enclosing them in plastic tents in the summer sun.
The results so far indicate that the right amount of exposure to excessive temperatures can completely eliminate the bacterium that causes the disease in protected potted plants in a nursery environment. If the plants are again exposed, unfortunately, they are infected again.
For plants in the ground under field conditions, the plants are freed of the bacterium in the leaves, but the treatment leaves the roots infected, as the high temperatures don't reach them. Under these field conditions, the plant gets a reprieve, with flushes up to six months after the treatment showing no sign of the disease. Previously existing symptomatic leaves remain. As time passes, the decline of the tree goes on.
Thermotherapy is one more arrow in the quiver of growers to mitigate the impact of HLB. Of course, its practical applicability is limited to smaller trees, and care is required to avert damage to trees from overly high temperatures.
In the dooryard setting, we may be able to use this method to keep our smaller trees in production . Figure 1, kindly provided by USDA, shows comparison of untreated and heated trees. Thanks to Paul Rusnak of Florida Grower for help with this article.