First report of Sirosporium diffusum causing brown leaf spot on Carya illinoinensis in Brazil.
Pecan (Carya illinoinensis) is economically important in the State of Rio Grande do Sul (RS), Brazil. During December 2013, brown leaf spot symptoms were observed in orchards and nurseries on up to 85% of the trees, being more severe on cultivars Barton, Desirable, Wichita, and Mahan. By early 2016, the disease was distributed throughout the state. Symptoms began in late spring on mature leaves as round, reddish-brown spots with a dark halo, measuring 0.5 to 1.5 cm in diameter, and progressed to cause severe defoliation by late summer. Pure cultures were obtained through single-spore isolation from young, reddish-brown leaf spots on 'Barton' from an orchard in Anta Gorda. Based on morphological characteristics, molecular data (sequence analysis of the partial region of tef1-α gene and the ITS region) and pathogenicity tests, the causal agent was identified as S. diffusum. This is thought to be the first report of S. diffusum causing brown leaf spot on C. illinoinensis in Brazil.