Cassava
(
Manihot esculenta)
Cassava
is a perennial woody shrub with an edible root, which grows in tropical
and subtropical areas of the world. Cassava originated from tropical
America and was first introduced into Africa in the Congo basin by the
Portuguese around 1558. Today, it is a dietary staple in much of
tropical Africa.
It is rich in carbohydrates, calcium, vitamins B
and C, and essential minerals. However, nutrient composition differs
according to variety and age of the harvested crop, and soil conditions,
climate, and other environmental factors during cultivation.
Importance
In sub-Saharan Africa (SSA) cassava is mainly a subsistence crop grown
for food by small-scale farmers who sell the surplus. It grows well in
poor soils with limited labor requirements. It provides food security
during conflicts when the invader cannot easily destroy or remove the
crop, since it conveniently grows underground. Cassava is usually
intercropped with vegetables, plantation crops (such as coconut, oil
palm, and coffee), yam, sweet potato, melon, maize, rice, groundnut, or
other legumes. The application of fertilizer remains limited among
small-scale farmers due to the high cost and lack of availability. Roots
can be harvested between 6 months and 3 years after planting.
Apart
from food, cassava is very versatile and its derivatives and starch are
applicable in many types of products such as foods, confectionery,
sweeteners, glues, plywood, textiles, paper, biodegradable products,
monosodium glutamate, and drugs. Cassava chips and pellets are used in
animal feed and alcohol production.
Production
More than 228 million tons of cassava were produced worldwide in 2007,
of which Africa accounted for 52%. In 2007, Nigeria produced 46 million
tons making it the world's largest producer. According to 2002 FAO
estimates, Africa exports only one ton of cassava annually.

Cassava
production depends on a supply of quality stem cuttings. The
multiplication rate of planting materials is very low compared to grain
crops, which are propagated by true seeds. In addition, cassava stem
cuttings are bulky and highly perishable as they dry up within a few
days.
Harvesting
Nineteen million
hectares of cassava were planted worldwide in 2007, with about 63% in
Africa. Cassava requires less labor than all other staple crops (21% in
working days as compared to maize, yam and rice). However, it requires
considerable postharvest labor because the roots are highly perishable
and must be processed into a storable form soon after harvest. Roots can
be harvested between six months and three years after planting.
Many varieties contain a substance called
cyanide
that can make the crop toxic if inadequately processed. Various
processing methods, such as grating, sun drying, and fermenting, are
used to reduce the cyanide content.
Consumption
Nearly every person in Africa eats around 80 kilograms of cassava per
year. It is estimated that 37% of dietary energy comes from cassava. The
Democratic Republic of Congo is the largest consumer of cassava in SSA,
followed by Nigeria.
Disease and constraints
The major pests
of cassava in SSA are the cassava green mite and the variegated
grasshopper. The main diseases affecting cassava are cassava mosaic
disease (CMD), cassava bacterial blight, cassava anthracnose disease,
and root rot. CMD alone accounted for an estimated 47% of East and
Central Africa's cassava production losses during a serious outbreak
beginning in the early 1990's until 2006. Pests, disease and poor
cultivation practices combined can cause yield losses as high as 50% in
all of Africa.
IITA's research and impact
IITA scientists have played a leading role in developing improved
cassava varieties which are disease- and pest-resistant, low in cyanide
content, drought-resistant, early maturing, and high yielding.
Disease-resistant varieties give sustainable yields of about 50% more
than local varieties. Distribution of CMD-resistant varieties in
response to the CMD outbreak in East and Central Africa resulted in
production levels recovering to pre-epidemic levels in less than five
years. Improved cassava varieties are now used in most cassava-growing
countries in SSA.
IITA's biological control program resulted in a
95% reduction in cassava mealybug damage and a 50% reduction in damage
caused by the cassava green mite.
Post-harvest strategies include
the development of effective and simple machines and tools that reduce
processing time and labor, and production losses. With these machines,
losses can be reduced by 50% and labor by 75%.
During the past
three decades, IITA has trained more than 9000 researchers and
technicians in ten African countries in processing and in new uses for
high quality cassava flour (HQCF). As a result, the private sector in
Madagascar, Nigeria, Tanzania, and Uganda have begun using HQCF as a raw
material for processing secondary products such as biscuits and
noodles.
Source: IITA