Sweet orange scab with a new scab disease 'syndrome' of citrus in the USA associated with Elsinoë australis

Elsinoe fawcettii causes citrus scab and E. australis causes sweet orange scab and there are different pathotypes of each species. Citrus scab is widely distributed, whereas sweet orange scab is limited mostly to southern South America. In 2010, E. australis was detected by PCR in Texas for the first time in the USA and subsequently found in commercial areas of Texas. In this study, cultures were obtained in Texas mostly from diseased fruit with symptoms similar to "late-season windscar" and identified as the Natsudaidai pathotype of E. australis by sequencing of the PCR amplification products and sequencing of the translation elongation factor and ITS regions. Inoculations of detached leaves and fruit of grapefruit, sweet orange, and tangerine produced scab-like symptoms on all organs and species. The fungus was re-isolated from the inoculated organs and PCR tests on re-isolated fungal colonies and lesions confirmed the presence of E. australis. The disease represents sweet orange scab of citrus with a new scab disease symptomatology, but the host range, ecology and epidemiology of this pathotype are still not completely understood. Thus far, Natsudaidai pathotype has been reported only from South Korea.