Vegetable
Manihot esculenta
Food Crop Diseases
Cassava Bacterial Blight
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| Cassava bacterial blight (CBB) is a serious bacterial disease of cassava caused by the bacterium Xanthomonas axonopodis pv. manihotis. It is widely distributed in Asia, Africa, and South America. The disease is a limiting factor in cassava production and can cause significant losses if not controlled. The pathogen spreads through infected cuttings and seeds. The bacterium Xanthomonas axonopodis pv. manihotis induces a wide range of symptoms in cassava plants. These include angular spots, blight, wilt, exudates and lesions in stems, and plant death. The infection begins with an epiphytic phase on leaves, which helps build inoculum. Leaf spots appear as moist, angular areas that are clearly distinguishable on the lower surface of leaves. The leaf blight is attributed to a toxin produced by Xanthomonas axonopodis pv. Manihotis. The bacterium colonizes the intercellular spaces in leaf mesophyll and multiplies rapidly, producing large quantities of exopolysaccharide matrix. The disease severity depends on various factors such as cultivar, soil fertility, climate, and quantity of inoculum present in the area1. Repeated cropping of highly susceptible varieties without rotation reduces soil fertility and increases the crop’s predisposition to the disease. |
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| Losses caused by CBB vary greatly. If environmental conditions are favorable for disease development and if no agronomic practices are adopted to control it, losses may reach 100% in only two or three cropping cycles. The disease spreads from one area to another and from one growth cycle to the next mainly through the planting of infected stakes. The severity of the disease depends on various factors such as cultivar, soil fertility, climate, and quantity of inoculum present in the area. Repeated cropping of highly susceptible varieties without rotation reduces soil fertility, which increases the crop’s predisposition to the disease. Xam excels in a humid subtropical to tropical climate. Plantations of Manihot esculenta often take place in soils characterized as arid, lacking in nutrients, and prone to erosion, especially when the cultivation occurs in sloped fields. |
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| Losses caused by CBB vary greatly. If environmental conditions are favorable for disease development and if no agronomic practices are adopted to control it, losses may reach 100% in only two or three cropping cycles. The disease spreads from one area to another and from one growth cycle to the next mainly through the planting of infected stakes. The severity of the disease depends on various factors such as cultivar, soil fertility, climate, and quantity of inoculum present in the area. Repeated cropping of highly susceptible varieties without rotation reduces soil fertility, which increases the crop’s predisposition to the disease. Xam excels in a humid subtropical to tropical climate. Plantations of Manihot esculenta often take place in soils characterized as arid, lacking in nutrients, and prone to erosion, especially when the cultivation occurs in sloped fields. |
Unknown
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Cassava Brown Leaf Spot
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| Cassava Brown Leaf Spot (CBL) is a fungal disease of cassava caused by the pathogen Passalora henningsii. It is one of the worst fungal diseases of cassava and is widely distributed in the tropics, including Asia, North and South America, the Caribbean, and Oceania. The disease appears as small brown spots with dark borders on the upper leaf surface. The spots are roundish and up to 15 mm in size, limited by veins, often with a yellow halo. The centres of the brown spots may fall out, leaving a hole in the leaf. During a severe attack, infected leaves become yellow and dry and may die early. The disease can greatly reduce yields. The fungus lives in diseased cassava leaves on the plant or those on the ground. It spreads to new leaves and plants by wind or rain splash. Good planting stock and hygiene are recommended to reduce CBL. Crop husks infected with CBL should be destroyed to reduce the disease spreading to the next planting. Early planting allows the crop to grow more vigorously, which helps reduce the damage that the disease causes to the plant. Removing dead leaves and diseased leaves on plants and burning them can prevent the spread of fungal spores. Using clean tools and protective gear can also avoid spreading spores. |
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