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Occurrence of target spot, caused by Corynespora cassiicola, on cotton plants in Dourados, Mato Grosso do Sul State.

Goulart, A. C. P. ; Lamas, F. M.

Summa Phytopathologica 2016 Vol 42 No. 3 pp. 271-272;

Abstract

Target spot or Corynespora leaf blight is a traditional soyabean disease caused by Corynespora cassiicola. This fungus is capable of infecting a large number of crop plants. On cotton, this disease was first reported in the state of Mato Grosso, Brazil, in 1995. In Mato Grosso do Sul State (MS), the first report of this disease on cotton was during the 2011/12 crop season. The symptoms of this disease on cotton plants are similar to those observed on soyabean plants. In the foliar phase of the disease, the symptoms first appear on the leaves in the lower canopy and spread upward through the canopy towards the shoot tips, characterized as small circular spots. The well developed lesions are necrotic and show typical "target spot" (concentric rings) symptoms, with alternating light and dark brown bands and depression at the centre of the lesion. Once multiple leaf spots appear, diseased leaves senesce, showing severe necrosis, and fall to the ground. In 2015, at the experimental field of Embrapa Western Agriculture, in Dourados, MS, cotton plants of the cultivars BRS 369 RF, FMT 709 and FM 975 WS showing typical symptoms of target spot were observed. Infected leaves were collected and taken to the laboratory for analysis. Based on the results of morphological observations and pathogenicity tests, the pathogen was identified as C. cassiicola.