Abstract

A cassava disease survey was conducted in four agroecological zones of Togo. High incidences of cassava bacterial blight, cassava mosaic disease and cercosporioses were observed across ecozones, while anthracnose disease was rare. Bacterial blight field incidences of 90.5% in the dry savanna zone, 70% in the forest savanna transition zone, 64% in the wet savanna zone and 52.6% in the forest zone, were recorded, with plant incidences ranging from 27.4% in the forest zone to 72.7% in the dry savanna zone. Mosaic disease field incidences were nearly 100% in all the ecozones and high plant incidences up to 86.9% were found. Cercospora leaf diseases – brown leaf spot, blight leaf spot and white leaf spot - occurred in all the ecozones with incidences ranging from 68 to 100%. Negative correlations between bacterial blight and mosaic disease, and between mosaic disease and white leaf spot were found, while brown leaf spot and blight leaf spot, brown leaf spot and white leaf spot, and blight leaf spot and white leaf spot were positively correlated. Field incidence of bacterial blight was positively correlated with plant age, ecozones - higher severity in dryer ecozones (P < 0.01), and weed density (P < 0.05). Further significant, but negative correlations occurred between bacterial blight and cercospora brown leaf spot on the other hand and vegetation type in the surroundings field (number of trees) (P < 0.05).Cercospora brown leaf spot was also significantly negatively associated with the number of crops in a field (intercropping) (P < 0.05), and Cercospora white leaf spot with sandy soils (P < 0.01). Results indicate that agroecological factors such as ecozone, plant age, weed density, vegetation type, intercropping and soil type and moisture influence disease occurrence and should be considered when developing integrated control measures.

Key  words: Blight leaf spot, brown leaf spot, cassava bacterial blight, cassava mosaic disease, white leaf spot, Cercospora henningsii, Cercospora caribaea, Cercospora vicosae, Colletotrichum gloeosporioides f. sp. manihotis, Manihot esculenta, Xanthomonas axonopodis pv. manihotis.