Agricultural Research Service

September 21, 1999

The invention is a way to biologically control various fungi that can cause fruit tree replant disease, specifically in apple trees. Replant disease is a major economic problem with apple growers, causing uneven growth, severe stunting, reduced productivity and tree death. Current methods to protect fruit trees from replant disease involve the use of chemical soil fumigants such as methyl bromide. However, the invention uses a Pseudomonas putida bacterial strain as a natural way to control disease-causing fungi. In Washington state alone, replant disease can result in a $40,000 reduction per acre in crop returns over a ten-year period. In addition, the Clean Air Act has prohibited the use of methyl bromide by 2001.

The invention can be produced using conventional fermentation methods. The invention can be formulated in a liquid carrier, or in formulations that include other strains to control different fruit tree diseases. The technology works best when applied as a root dip. The invention can also be applied directly to the soil in both a solid and liquid form. Treated ground should be watered immediately to facilitate movement of the biocontrol into the root zone and to enhance survival of the beneficial strain. The invention can lead to an increase in the trunk cross-sectional area, increased shoot elongation, and increases in root and shoot weights compared with non-treated plants.

Mark Mazzola
Physiology/Pathology Tree Fruits
Wenatchee, Washington 98801
(509) 664-2280 / Fax: (509) 664-2287

fungicides, biocides, biocontrol products, fruit trees, root dip, Pseudomonas putida