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First Report of Black Sigatoka in Bolivia

Black Sigatoka, caused by Mycosphaerella fijiensis, is the most important disease of banana worldwide (1). It affects cultivars of the Cavendish subgroup that are used for export and important, locally consumed cooking and dessert bananas and plantains, reducing yields by 50% or more. Black Sigatoka first appeared in the Western Hemisphere in 1972 in Honduras, and has spread to all other countries in Central America (1980), Mexico (1980), and the following islands in the Caribbean: Cuba (1992), Hispanola (Dominican Republic) (1996), and Jamaica (1994). In South America, the disease has spread to Colombia (1981), Ecuador (1986), Venezuela (1992), and Peru (1994) (1). In June 1996, symptoms of the disease were observed in the San Carlos area in the western Chapare region of Bolivia. During surveys conducted in March and June 1997, several Cavendish clones, Dulce Cajita (Pisang mas), Guineo (Silk), Morado (Red), and Platano (French and Horn plantain) were affected. In each of eight major banana-producing areas in the region, disease incidence and severity were recorded at several representative sites on Cavendish cultivars, which were the most widely spread and susceptible clones in the region. Disease incidence was 100% in all areas from San Carlos to Ingavi B, 30 km to the east, and disease severity, rated as the youngest leaf spotted (YLS), ranged from means of 4.5 to 8 in the same areas. The disease was less common or rare in the Valle Sajta area, 60 km east of San Carlos, the reserve of the Yuqui indigenous group at the confluence of the Rio Chimore and Rio Useuta, 15 km northeast of San Carlos, and the southernmost settlements of the Yuracare indigenous group on the Rio Chapare, 20 km north of Ingavi B (incidences = 0 to 50%). Symptoms began as brown streaks on the abaxial leaf surface, 1 to 3 mm in length, and became visible on the adaxial surface and enlarged to wet, dark brown streaks, 1 to 2 × 10 to 20 mm, with chlorotic haloes. Ultimately, large portions of the leaf became blackened and watersoaked. The presence of the disease in the San Carlos, Ingavi B, and Senda B areas and the Yuqui reserve was confirmed after microscopic examination of the anamorph, Paracercospora fijiensis, on affected leaf tissue: scars were present on the base of conidia, and only simple conidiophores were found (2). This is the first report of black Sigatoka in Bolivia, and represents the southernmost extent of the disease on the South American continent. High rainfall in western portions of the Chapare (4 to 7 meters per year) makes it unlikely that the disease could be controlled effectively or economically in the region with fungicides. We believe this is the closest approach of the disease to Brazil (ca. 700 km), the last major banana-producing country in which black Sigatoka has not been reported. Moreover, the outbreaks in the northern Chapare are thought to be the first across the colonist frontier to indigenous Amazonian populations that rely on plantains and bananas as staple foods.

References: (1) X. Mourichon and R. A. Fullerton. Fruits 45:213, 1990; (2) N. Pons. Trans. Br. Mycol. Soc. 89:120, 1987.