Sweet orange scab of citrus was found recently on a satsuma tree in Orange, Texas about 3.5 miles west of the Texas-Louisiana border. Unlike citrus (or sour orange) scab caused by Elsinoë fawcetti, which normally occurs in the southern U.S., sweet orange scab caused by Elsinoë australis was previously reported only from South America. The primary difference between the two diseases is with regard to their host ranges. Whereas citrus scab commonly occurs on lemons, tangerines, grapefruit and satsumas, it rarely occurs on sweet oranges. In contrast, sweet orange scab occurs primarily on sweet oranges, tangerines and satsumas. USDA-APHIS-PPQ initiated a survey for sweet orange scab within a 1-mile radius of the infected tree in Texas this past weekend. They will begin to check citrus in Calcasieu Parish for the disease sometime this week.
If you find scab on citrus, particularly those of you in the western part of the state, please send samples to the Plant Disease Diagnostic Clinic. We will forward them to the USDA lab in Beltsville, MD for identification.