Cassava Bacterial Blight disease (CBB) is caused by a bacteria called Xanothomas axonopodis pv. manihotis.
It infests the internal parts of cassava leaves and stems beginning at the tiny lesions formed in-between the leaf veins.
CBB resemble small roundish water-soaked dead spots that usually start as scattered dots with angular edges. The lesions or spots later merged into larger patches completely killing the cassava leaf.
MODE OF TRANSMISSION AND CONTROL
The main source of CBB is cassava plants already infested. This bacterium enters cassava plants through wounds and scratches sustained on stems and leaves. When multiply into large colonies it spreads to other cassava crops.
If the crop is not destroy after root harvest, dead cassava stems and leaves with the bacterium serve as reservoir for the disease. The disease is spread naturally by raindrops which splash the bacterium from infected plants onto healthy plants. When insects for example grasshoppers
feed on disease cassava plant they become contaminated with the bacterium and spread it to healthy cassava plants as well.
Farm tools that are used to cut infected cassava plants should be cleaned after use to prevent the bacterium spreading to other plants.
All plants suspected of the CBB should be rogued and completely destroyed.
Visible signs of CBB start from the leaf blade and migrate toward the petiole making the leaves brownish when severed. Other
signs of CBB includes the appearance of brown gum stains on the leafs, petioles and stems of infested cassava plants.