Why the quality of cassava roots
matters to Kinazi Cassava Plant
C
assava (Manihot esculenta
Crantz) is a root crop that is
widely cultivated in the tropical and subtropical countries
and provides inexpensive
source of dietary calories for over 200
million people in sub-Saharan Africa. According to Food and Agriculture Organization (FAO) figures, Africa produces approximately 140 million metric tonnes
of cassava, which is higher than any
other crop including maize. In addition,
FAO predicts that cassava is going to be
the next Africa’s cash crop because it is
processed into starch, which can be utilized as a raw material for several industries such as food, pharmaceutical, textile, ethanol, brewing, paper and wood,
and other related industries. Addition
of cassava to a list of Rwandan priority
crops and establishment of Kinazi Cassava Plant (KCP) by the Government of
Rwanda indicates that cassava is viewed
as a crop that is believed to ensure food
security and move millions of Rwandans
out of poverty. However, cassava production is hampered by root rot disease,
which significantly reduces the quantity
and quality of cassava roots.
A heap of fleshly harvested cassava roots
cultural practices can cause yield losses
that may be as high as 50%. The following are the ways by which cassava diseases the yield of cassava:
1. What is cassava root rot disease?
Cassava root rot disease is caused by
various kinds of fungi living on or in
the soil. These fungi are mainly found in
soils that do not drain properly and can
also infect cassava roots that have been
planted in forests that have been recently cleared.
2. What are the symptoms of cassava
root rot disease?
Cassava plants whose roots are decaying
due to root rot disease have the following characteristics:
• The leaves of cassava plant affected by root rot disease turn brown,
wilt, and the plant may appear
slightly burned even during rainy
season,
• Wilting results in defoliation;
• Cassava root rot disease kills both
the feeder and storage roots;
• Cassava roots may unexpectedly
swell and turn light brown;
• The roots give out unpleasant
smell when cut open;
• Cassava roots appear colored
when cut open.
3. How is cassava root rot disease
spread?
The common sources of cassava root rot
disease are soils as well as cassava root
and stem debris contaminated with fungi. These microorganisms can easily find
their way into the plant through wounds
caused by pests or farming tools. Fungi
may also pierce the roots by themselves.
Farm tillage tools used in cassava farms
with the disease should be cleaned after
i)
Cassava root damaged by root rot disease
use to prevent the fungi on them from spreading
to other areas. Also, cassava plant debris in farms
with root rot should be burned because they may
serve as the vectors of root rot fungi.
4. How can root rot disease be controlled?
• Use cassava varieties that are resistant to
diseases,
• Avoid planting cassava in an area that is
prone to flooding;
• Plant cassava in a sandy loamy soil;
• Always a good idea to practice crop rotation;
• Avoid planting cassava as the first crop after clearing woodland or forest.
5. How are cassava diseases able to reduce
the yield of cassava?
In Africa, cassava diseases coupled with poor
Loss of roots: Cassava root rot
and cassava brown streak diseases attack cassava roots and
cause immediate and direct
losses. By damaging leaves and
stems, cassava diseases interfere with the process by which
cassava manufactures its own
food that is stored in the roots.
This ultimately reduces plant
growth and development of cassava roots;
ii) Loss of healthy planting material: Cassava diseases can
contaminate cassava stems and
make cuttings inappropriate for
planting. Certain cassava diseases such as cassava bacterial
blight, cassava anthracnose, and
cassava brown streak diseases,
reduce the quantity and quality
of planting material by causing
shoot tip die-back. Cassava bud
necrosis kills stem buds (eyes),
which reduces the ability of cuttings to germinate;
iii) Loss of leaves: This is a serious
problem especially in countries
where cassava leaves are used
to prepare a special vegetable
soup. In Rwanda, Isombe is a
popular vegetable and therefore
loss of cassava leaves deprives
consumers of this special dish.
Diseases that lead to cassava defoliation include cassava bacterial blight and cassava anthracnose whereas diseases that lead
to discoloration and distortion
are cassava mosaic disease and
cassava brown streak respectively. Such leaf damages reduce
the ability of cassava plants to
make sufficient food for storage
in the roots.
6. Why cassava root rot disease
matters to KCP and cassava
farmers
• To KCP: It is important to understand that high quality cassava
flour is obtained from high quality cassava roots. As a company
whose mission is to process cassava flour of the highest quality, KCP
has zero tolerance towards rotten
cassava roots. The staff of KCP especially those in the Agronomy,
Production and Quality Assurance
Departments are trained to ensure that KCP obtains high quality
cassava roots from farmers.
•
To cassava farmers: Root rot
disease can easily destroy the
entire cassava plantation. Such a
loss would put cassava farmers
in a very difficult situation especially those who obtain bank
loans to grow cassava. Cassava
farmers are therefore advised to
strictly adhere to the guidelines
that are always provided by the
Ministry of Agriculture (MINAGRI) through Rwanda Agriculture
Board (RAB) on how to avoid the
risks of root rot disease. In the
mean time, RAB is actively working with the International Institute of Tropical Agriculture (IITA)
to find a way of introducing cassava varieties that are resistant to
root rot disease.