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Minimizing potential potato storage loss is always a major concern for storage managers. Stakeholder and other industry inputs have indicated disease control needs for processing, fresh market and seed potatoes as an area of research emphasis. Post-harvest applications of either sprout- or disease-control agents to tubers are often made to help maintain quality prior to entering the storage facility and after leaving the packing shed. There are very limited data on the impacts from the use of post-harvest disease-control agents on wound healing. The potato industry has gained a few novel post-harvest products in the last several years although there is still a paucity of post-harvest chemicals and/or application methodologies available to the industry. The lack of effective products to control disease in storage prompted the industry to support and evaluate the use of additional control agents in storage. Products with low food safety concern need to be tested as viable post-harvest disease-control agents. Research information will help establish recommendations on the use of post-harvest disease-control products and if additional alternative products or methods need to be identified. <P>
The objectives of this study are to: <OL> <LI> Evaluate the effects of handling situations for various cultivars and post-harvest product applications on disease development in storage <LI> Investigate disinfestants, fungicides and biocontrol agents for disease control in storage. </OL> Information derived from this research will be disseminated to the potato industry via website postings, conference presentations and workshops, popular press articles and journal articles.
NON-TECHNICAL SUMMARY: The quality and volume of potatoes can be substantially lowered in a relatively short amount of time if proper storage practices are not employed. Nearly 82% of the potatoes produced in Idaho are stored for some duration. In most years, a loss in storage due to shrink and disease is approximately 6 to 7% but can be higher if frost or wet rots have affected the crop. Minimizing potential storage loss is always a major concern for storage managers. Stakeholder and other industry inputs have indicated disease control needs for processing, fresh market and seed potatoes as an area of research emphasis. It is important to minimize wounding of the crop during harvest and handling to reduce susceptibility to many storage diseases. The impact of wounding and predisposition to disease development can also be influenced by cultivar, pulp temperatures and storage conditions. Post-harvest applications of either sprout- or disease-control agents to tubers are often made to help maintain quality prior to entering the storage facility and after leaving the packing shed. There are very limited data on the impacts from the use of post-harvest disease-control agents on wound healing. The use of phosphorous acids as a low-pressure spray application on potatoes being loaded into the storage facility is gaining nationwide acceptance. This product is very effective in minimizing the spread of pink rot and late blight in storage. There is currently no data on the impact of wound healing in storage after applications of this product. Additional products being used in the industry include disinfestants applied on either potatoes going into storage or just prior to being packaged and shipped. Additionally, for both the organic and conventional markets, microbial biocontrol agents are also being considered. Again, there is limited information on these post-harvest products on the potential effects on wound healing, efficacy and subsequent tuber quality. Data on this response would be beneficial to fully recognize the use and impacts of these post-harvest disease-control agents. The potato industry has gained a few novel post-harvest products in the last several years although there is still a paucity of post-harvest chemicals and/or application methodologies available to the industry. The lack of effective products to control disease in storage prompted the industry to support and evaluate the use of additional control agents in storage. Products with low food safety concern need to be tested as viable post-harvest disease-control agents. Research information will help establish recommendations on the use of post-harvest disease-control products and if additional alternative products or methods need to be identified. Various methods of applications, such as application via aerosol or humidification, may need to be implemented in some situations to elevate efficacy. The impact of this project will be to provide research based information to the potato industry regarding storage management of diseases and the use of post-harvest disease control products. <P>
APPROACH: <BR>
Objective 1. Various cultivars will be grown and harvested at the University of Idaho Kimberly R & E Center. Potatoes will be evaluated at various pulp temperatures, wounded or not, inoculated with various storage disease organisms, treated with various post-harvest products and stored for the appropriate amount of time. Expansion of these protocols will be enacted when necessary to develop an overall disease control management program for specific cultivars. To investigate the potential interference of wound healing with a post-harvest application, potato tubers will be grown and harvested at the University of Idaho Kimberly R & E Center. Tubers will be cut into similar sized pieces with comparable cut surface area and treated with the following post-harvest disease control agents: a) phosphorous acid (1:5); b) hydrogen peroxide/peracetic acid mixture (1:50); c) biocontrol microbial agents; and d) untreated control. Three subsets of treated tubers will be used to answer the objectives of the study. 1) A subsample of cut and treated tubers will be weighed periodically to determine weight loss over time (up to 14 days). 2) A second subsample will be evaluated for suberin and wound periderm development. A thin-slice non-staining technique will be used. Each slice will be examined under a UV microscope and the number of suberized cell will be counted and the presence of the wound periderm layer will be evaluated. Slices will be examined 4 to 5 times during the first 14 days after treatment. 3) A third subsample will be tested for potential disease development of Fusarium dry rot. Evaluations will include simple "bag tests" to assess susceptibility to disease development as well as inoculation treatments with Fusarium spp. <BR><BR>Objective 2. Healthy potato tubers inoculated by applications of Phytophthora erythroseptica (pink rot), Phytophthora infestans (late blight), and Fusarium sambucinum (dry rot) or naturally infected tubers with Helminthosporium solani (silver scurf) will be used in these studies. Additional diseases will be evaluated as needed for the Idaho potato industry. Using a Research Track Spray Cabinet (set at 37 speed, 42 PSI) the inoculated tubers will be sprayed with test treatments at the rate of 0.5 gal spray volume per ton of tubers. Post harvest products may include fungicides, disinfestants, and biological control agents. These treatments simulate an application with a low-pressure boom sprayer as potatoes are being loaded into the storage. Tubers will be placed into storage for a predetermined time and temperature based upon the organism evaluated. Tubers will be evaluated for incidence and severity (percentage of tuber showing symptoms) of infection.Products that show strong potential for controlling disease will be investigated further for appropriate rates and application methodology. Additional application methodology may include thermal or cold aerosol and application via a humidification system.