The below is intended to provide general information on the importance of foliar fungal diseases on different citrus varieties destined for the fresh market and for processing. Since many fungal diseases only affect the external appearance of the fruit, most diseases have little importance on fruit for processing.
Greasy spot is a universal problem on all varieties and Postbloom fruit drop and Phytophthora brown rot cause severe losses in some locations in years that are favorable for disease development. Disease management on groves intended for processing is not complex.
However, on fresh fruit varieties such as grapefruit, Navel oranges and most of the tangerine and tangerine hybrids, fungal diseases are very important in Florida’s humid climate. Intensive spray programs may be needed to produce blemish-free fruit, especially on varieties susceptible to Alternaria brown spot.
Products available for control of fungal diseases are few and a great deal of ingenuity is needed to produce high quality fresh fruit.