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Leaf Spot of Bananas Caused by Mycosphaerella musicola: Role of Conidia in Epidemiology. R. H. Stover, Tropical Research Department, Tela Railroad Company (a subsidiary of the United Fruit Company), La Lima, Honduras. Phytopathology 60:856-860. Accepted for publication 16 December 1969. DOI: 10.1094/Phyto-60-856.

Conidial production was greater on the upper than on the lower surface of banana leaf spots, and began when the lesion caused by Mycosphaerella musicola turned from pale brown to dark brown or black. Conidial sporulation ceased or was greatly diminished when the center of the spot began to turn gray, and did not occur on older spots with gray centers. An average of 5.3 crops of conidia were produced/spot on young plants. Sporulation occurred on successive nights in the absence of rain, provided dew was present, then ceased after a maximum of 12 crops of conidia had been produced. In areas of mass infection where mass necrosis occurred (leaf “burning”), conidial production was reduced about 50%. Conidia, when mature, readily floated off the sporodochia in morning dew or rain water. Conidia were responsible for maintaining various levels of infection in sprayed and unsprayed bananas during prolonged rain-free periods. In the absence of rainy weather favorable for ascospore production and dissemination, conidia were the major source of inoculum responsible for spotting. The amount and prevalence of this spotting was less than in rainy weather and was dependent on dew formation.