WSU Tree Fruit Research & Extension Center

Postharvest Disease Guide

Tuesday, September 26, 2017

The production of apples and pears is a complex process involving orchard, storage and marketing phases. Modern postharvest technologies make the long-term storage of apples and pears possible. In Washington State, apples may be stored for up to 12 months and winter pears for up to nine months. Postharvest diseases can be a limiting factor for the long-term storage of fruits. Losses as high as 50-60% in storage bins prior to packing have been observed. Instances of severe decay on packed fruit in the boxes have also been observed. Fruit decay and repacking of fruit due to decay cost the fruit industry millions of dollars in losses each year. Decay management has been considered one of essential components in a profitable production system for pome fruits.

Because of the complexity of production process, we are dealing with postharvest diseases in two phases: fruit decay in storage bins before packing and fruit decay after packing (Fig. 1). Several postharvest diseases commonly occur on apples and pears during storage. Depending on the nature of postharvest diseases, some diseases originate from infection in the orchard, whereas some are more commonly associated with postharvest handling process. Orchard practices, such as sanitation and fungicide applications, insect control, and fruit handling practices after harvest prior to storage, can have great impacts on the types and amount of decay in storage bins as well as the decay on packed fruit in the boxes, whereas sanitizing the water system and fungicide applications at packing are critical to reducing amount of decay on packed fruit. Control of postharvest decay should start in the orchard and complete when the fruit are sold.

Accurate diagnoses of postharvest diseases are the first step to implement relevant practices to control the problems. This publication is intended to provide visual aids and symptoms descriptions for diagnoses of common postharvest diseases on apples and pears commercially grown in the Pacific Northwest as well as general recommendations for disease control.

Tree Fruit Research & Extension Center, 1100 N Western Ave, Washington State University, Wenatchee WA 98801, 509-663-8181, Contact Us