Hot water shower against Gloeosporium fruit rot in organic apple production – how to introduce a new system from research to practice

Abstract: Gloeosporium rot is the main storage disease in organic apple production in Austria and in untreated orchards losses can be up to 80%. The problem in organic fruit growing is not only to find a product or method with a high efficacy against Gloeosporium rot but also against different fungal diseases including apple scab, sooty blotch and Marssonina coronaria during the growing season. Using different fungicides or plant strengtheners together or alternating them could lead to potential phytotoxicity. Applying control methods against Gloeosporium rot postharvest may provide more control than applying treatments during the growing season. In 2009 and 2010 different orchard treatments were treated with products commonly used in organic apple production, such as copper-oxychloride, potassium bicarbonate + sulphur, and acidified clay powder (Mycosin) either alone or in combination with postharvest immersion in hot water. None of the orchard treatments were effective. However, superior results were obtained with the hot water dipping. The objective of the study was to develop hot water treatments for larger-scale commercial applications. Showering fruit with hot water provided logistical advantages over the immersion method. The efficacy of the hot water shower machine developed for the prevention of Gloeosporium rot is approximately 80% comparable to the degree of disease suppression obtained through the use of chemical fungicides. In 2013, hot water showers were used to treat over 4.5 million kg of apples. Under certain conditions heat damage occurred on the apples. However, there is potential to improve the efficacy of the hot water shower system by optimizing the shower time and temperature.