Common Cassava Diseases
1. Cassava Mosaic Disease (CMD)
The disease is transmitted by a virus called Cassava Mosaic Virus (CMV); This virus is spread by a kind of fly called ’’Bemisia tabaci’’. The disease is widespread across Africa.
Symptoms:
Attacked leaves have irregular yellowish spots. While green parts pursue their development; leaves deform, blister, become narrow and shrivel up.
Means of fighting against the disease
Uproot any plant on which symptoms of the disease are identified, plant timely using healthy cuttings from resistant species and from healthy plantation. Ensure appropriate management of the plantation.
2. Cassava Bacterial Blight (CBB)
Symptoms include blight, wilting, dieback, and vascular necrosis. A more diagnostic symptom visible in cassava with X. axonopodis infection are angular necrotic spotting of the leaves—often with a chlorotic ring encircling the spots. These spots begin as distinguishable moist, brown lesions normally restricted to the bottom of the plant until they enlarge and coalesce—often killing the entire leaf.
3. Cassava Brown Streak Virus Disease (CBSV)
Cassava brown streak virus disease (CBSD) is a damaging disease of cassava plants, and is especially troublesome in East Africa. It was first identified in 1936 in Tanzania, and has spread to other coastal areas of East Africa, from Kenya to Mozambique. CBSD is characterized by severe chlorosis and necrosis on infected leaves, giving them a yellowish, mottled appearance.. Leaf symptoms vary greatly depending on a variety of factors. The growing conditions (i.e. altitude, rainfall quantity), plant age, and the virus species account for these differences. Brown streaks may appear on the stems of the cassava plant. Also, a dry brown-black necrotic rot of the cassava tuber exists, which may progress from a small lesion to the whole root. Finally, the roots can become constricted due to the tuber rot, stunting growth.
Common Cassava Pests
Cassava mealybug is a 2-3 cm long pink colored insect whose body is covered with wax producing pores. Cassava mealybugs spread especially in hot season by wind and planting infested cuttings from infected field. These insects gather on some spots of cassava tender leaves and infected stems have shrub like leaves and their growth is stunt and stems are distorted.
Cassava green mite is transmitted by a green acaridian called Mononychellus tanajoa which inflicts heavy damages to cassava fields during dry seasons. Many yellow spots appear on the leaves and on branch ends.
The leaves get green, interspersed with yellow spots. Attacked leaves get weak and fall, and the partly stripped stem remains only with small leaves in the shape of claws; the growth slows down and internodes are short.
The whitefly, Bemisia tabaci, is a major pest of cassava, particularly in Africa where it is responsible both for the transmission of plant viruses and, increasingly, for direct damage due to feeding by high populations.
Control measures for Cassava diseases and pests
RWA
ENG