Management of Onion Diseases

Recently the Vidalia onion industry has been pressed with a number of issues. The industry is facing greater competition during its traditional window for sales. Much of that competition is from foreign sources, but there also has been increased interest in producing sweet onions elsewhere in the U.S. Any issue that increases production costs while also decreasing quality will have a negative impact on the onion industry as it struggles to remain competitive in the global economy. One area of concern is quality of the onion product. Postharvest diseases of onions traditionally have been very difficult to manage and have consistently been responsible for major economic losses in stored onions over the years. A team of researchers from the University of Georgia, Auburn University, Colorado State University, Mississippi State University and the University of Idaho, representing multi-disciplines that include Plant Pathology, Agricultural and Biological Engineering, Agricultural Economics, Entomology, Food Science, Horticulture, and Rural Sociology secured a SCRI grant to address the situation. The response from this program was multi-faceted. First experiments were conducted in the field using crop rotation and double-cropping methods to develop a crop rotation system that would utilize three successive plantings of "suppressive" crops to reduce sour skin. Second, this program identified current and new threats to onions in the field and storage and took the approach that management in the field was the first line of defense to reduce losses in storage. Third, this program worked closely with entomologists in attempts to better understand how center rot of onion develops and the importance of the vector relationship with thrips. Finally, this program worked closely with horticulturists to evaluate postharvest treatments, specifically pesticide drenches, as a means to reduce rots in storage.