Richard C. Bogren, Graham, Charles J.
News Release Distributed 10/27/10
The LSU AgCenter has received a U.S. Department of Agriculture grant to study a new control for pecan scab disease.
The two-year grant for $22,400 came through the Louisiana Department of Agriculture and Forestry as part of a USDA program to support research in specialty crops, which include fruits, vegetables, nuts, horticulture and nursery crops.
The pecan research will be conducted by Charlie Graham, an LSU AgCenter plant physiologist at the AgCenter Pecan Research/Extension Station in Shreveport.
“The disease doesn’t pick its place,” Graham said, pointing out it can occur in single trees in homeowners’ backyards or in large commercial orchards.
Graham is working with chemicals called phosphites that were first identified to control pecan scab in a 2007 study of another chemical. In that study, “it gave great control of scab in a foliar application,” Graham said.
The new study is evaluating phosphite-based fungicides as ground-applied, systemic controls for pecan scab. A systemic material is taken up by the tree’s roots and travels throughout the plant. In this case, the phosphite would be present in the leaves and nuts, killing any of the scab-causing fungi that try to infect them.
“We know other chemicals have worked systemically to control insects,” Graham said of phosphite. “Now we want to find out if phosphite can systemically control a pecan disease.”
“Phosphite provided excellent control as a foliar spray in an earlier study,” Graham said. Now, he wants to learn if it can be as effective when it’s ground-applied.
Most fungicides work by covering the nut and leaves with a layer of chemical that prevents the fungi from infecting the plant, Graham said. But because those foliar-applied products eventually disappear, the trees have to be sprayed every two to four weeks during the growing season.
“That means six to eight and up to 10 foliar applications,” Graham said. “In the test, a soil-applied fungicide will be applied only twice. That’s a considerable cost savings.”
A ground-applied fungicide that only needs to be used twice a season will give homeowners and small orchards a product that doesn’t need to be applied with large, expensive spray equipment most don’t have or can afford.
In other tests with other crops, phosphite has been stable in the plants. “It stays in place,” Graham said.
Various fungicides with brand names like Fosphite, Rampart and Phostol contain potassium, sodium and/or ammonium phosphites, which have been combined with an alkali salt to reduce acidity, Graham said. Along with evaluating phosphite itself, Graham’s study also will look at how the chemical activity is affected by other components of the various products.
The LSU AgCenter and the LSU College of Agriculture