As the ban of two antibiotics used to treat fire blight in organic pear and apple orchards looms, two organic alternatives appear promising.
Researchers have found that a yeast-based product as well as a new water-soluble copper provides protection from the potentially devastating disease, according to a news release.
Based on actions by the National Organics Standards Board, organic growers will no longer be able to use oxytetracycline and possibly streptomycin after the end of this season.
The antibiotics have been used to control fire flight, which kills infected branches, eventually debilitating trees. Outside of antibiotics, the only way to manage fire blight was to prune out infected limbs.
The antibiotics, although not organic, had been allowed for organic production because no other alternative was available.
Trials conducted by Oregon State University involved applications of Blossom Protect, a yeast that clings to apple and pear blossoms and prevents colonization by fire blight bacterial.
The product was developed in Europe and registered for U.S. use by the Environmental Protection Agency in 2012.
In the trials, it was 90 percent effective when sprayed after lime sulfur to reduce crop load.
Copper has been used for fire blight for almost a century. But heavy applications can be toxic to trees and cause russetting on fruit.
But new water-soluble formulations, including Cueva and Previsto, contain lower concentrations of the metal, which reduces the negative effects while still controlling fire blight.