Cassava

• Land preparation for planting cassava on upland and in valleys differs: On upland, farmers plant on flat ground, or mounds and ridges. In valleys, farmers prepare ridges or mounds above ground level to control water logging.
• Mounds range from 30 to 60 cm high.
• The space between mounds varies from 60 to 100 cm.
• Plow and harrow the field twice. Do these operations when there is enough soil moisture. Plow the field at least 15-30 cm deep.

PLANTING

• Planting date lies between September and November each year,
• Ideally, grow cassava plants from semi-hardwood cuttings;
•  Healthy, fresh stem cuttings from mature plants are best for planting The quality of cassava stem cuttings depends on:

– age of stem

– thickness

– number of nodes

– health of stems

• Take stem cuttings from plants which are between 8 and 18 months old.
• Use thick stems, do not use thin stems
• Use 20-30 cm long cuttings with 5-7 nodes
• Select planting material from healthy plants
• Cut stems when you are ready for planting
• Cut stems with a well-sharpened machete, knife, or saw.
• Plant as early as possible, just before the rains or after the rains begin
• Plant cassava cuttings vertically, at an angle, or horizontally
• In a monocrop, space cassava 80-100 cm within and between rows.
•  Although no universal recommendation exists, in Africa, a plant density of 10 000-15 000 plants/ha gives a good crop.

1. Weeding

• Weed competition reduces canopy development and root bulking.
•  Hand weeding is effective on small farms, therefore hand weeding is common among small-scale cassava farmers and weed at 3, 8, and 12 weeks after planting.

2. Fertilization

Cultivation of cassava is widespread due to its ability to grow in poor soils.

In traditional farming, without fertilizers, farmers can obtain yields of 5-6 t/ha on soils that would not support other crops. However, for good growth and yields, cassava requires a balanced amount of plant nutrients. Recommendation is 300 kg (NPK)/ha, and 20 to 30 t/ha of organic manure.

3. Multiple cropping

• Intercropping suppress weed infestation, reduce soil temperature, retain higher soil moisture, and produce more organic matter than sole cropping or simple mixtures.
• Nutrient loss from erosion in complex mixtures is less than in sole cropping. Cassava is often intercropped with maize, beans and groundnuts.

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 (CM)

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 (CGM)

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.

• Bemisia whitefly

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

• Grow tolerant varieties
• Use clean planting materials and plant on time when the first rains start
• Roguing (Phytosanitation)
• Training (educating farmers/users)
• Strict quarantine regulations
• Biological control (natural enemies)
• Exchange of germplasm with tissue culture plantlets
• IPM (Integreted Pest Management)

• Early-maturing varieties are ready for harvesting at 8 months, while late-maturing

varieties are ready 18 months after planting.

• Farmers do not usually harvest all the plants on a plot at the same time. Farmers harvest only the quantity required for immediate use. Harvesting is easier when the soil is moist.
• Harvesting is also easier if planting is on ridges
• The yield depends on grown varieties: old varieties used to yield 15-25 Tons/Ha but current improved varieties are growing well: NASE 14 yields  30-35Tons/ Ha  while NAROClass1 yields 35-50Tons/Ha .

Almost all cassava grown in Africa is for human consumption; 30 percent is consumed after

peeling, cleaning and boiling, while 70 percent is processed into a wide variety of food

products including dry chips and flour, cooked pastes, roasted or steamed granules, beverages, etc. Both rural and urban peoples use these products as a basic daily source of dietary energy.

In Rwanda, We have the following cassava products:

• Ugali or fufu refers to the dough made from  cassava flour. This flour can be obtained in two ways: sun drying of fresh cassava whole roots or chips and milling them into flour when dry; or first soaking whole roots in water for 3 to 5 days. Soaking is usually the preferred process if water is in abundance; where water is scarce, cassava flour is made from sun -dried roots.
• Gari: a free flowing, granular, fermented and gelatinised cassava product. Easy to store and fast to cook, gari is a convenient food well suited for a busy urban lifestyle.
• Food processing factories are mixing cassava flour and wheat flour in the production of biscuits, bread, cakes,….
• Starch is being produced industrially,
• Kwanga (or chickwangue) is a popular fermented cassava product. To make it, cassava roots fermented by three days of soaking in water are mashed and steamed. The steamed mash is kneaded into smooth dough which is wrapped in leaves and steamed. After steaming, the wrapped cassava is allowed to cool. The product can be consumed warm or cold. Its shelf life is about 3 to 7 days at room temperature if the wrapping is not open. Otherwise it will dry up and become unfit for eating or it will support microbial growth.
• Cassava leaves: young tender leaves are usually selected, pounded and boiled for 15 to 30 minutes; various ingredients are then added to taste.