| Sumario: | The “torbo” disease has been known in Costa Rica for a long time. Young potato plants become wilted because of root rotting and canker formation at the base of the stem. In adult plants, the tuber appears covered with a white fungus mat that turns dark with age, almost black, resulting in a hard rugose skin. In cross sections, the tuber will show a cortical band of necrotic streaks, radially arranged, that correspond to the growth of rhizomorphs from a fungus whose characteristics belong to the genus Rosellinia. Evidence was obtained of the existence of more than one strain of the fungus, which differed in pathogenicity and colony features.
Field experiments for the control of the disease were made in the northern part of Cartago, Costa Rica, using several fungicides. Vapam and Terraclor were statistically significant in the control of the disease during dry season conditions, but were not as effective when very moist weather was prevalent.
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