In March 2010, citrus black spot symptoms were observed on sweet orange trees in a grove near Immokalee, Florida, USA. Symptoms observed on fruit included hard spot, cracked spot and early virulent spot. Hard spot lesions were up to 5 mm, depressed with a chocolate margin and a necrotic, tan centre, often with black pycnidia (140-200 m) present. Cracked spot lesions were large (15 mm), dark brown, with diffuse margins and raised cracks. In some cases, hard spots formed in the centre of lesions. Early virulent spot lesions were small (up to 7 mm long), bright red, irregular, indented and often with many pycnidia. In addition, small (2-3 mm), elliptical, reddish brown leaf lesions with depressed tan centres were observed on some trees with symptomatic fruit. Chlorotic halos appeared as they aged. Most leaves had single lesions, occasionally up to 4 per leaf. The causal organism was identified as Guignardia citricarpa based on cultural, morphological and genetic (ITS) analyses. This is thought to be the first report of black spot in North America.
