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I S R A
DRCSP
Institut Sénégalais
Direction des Recherches sur les
de Recherches Agricoles
Cultures et Systèmes Pluviaux
COWPEA PRODUCTION BULLETIN FOR SENEGAL
Anthony E. Hall”, Ndiaga Cisse, Samba Thiaw,
Mbaye Ndiaye, Mbene Dieye Paye, and Mamadou Balde
1
CNRA
Centre National de Recherches
Agronomiques de Bambey
Bambey BP53
SIENEGAL
*Dep,artment of Botany and Plant Sciences
University of California
Riverside, CA 92521-0124, U.S.A.
1996
F&IA
INTRODUCTION
W%
Cowpea (Signa unguiculata (L.) Walp.) was domesticated in West Africa and has been cultivated
there for thousands of years. It was distributed to other parts of Africa and other continents by the
migration of people and trade. West Africa still has the major area of cowpea cultivation in the world.
In Senegal the area of cowpea production during 1980 to 1994 varied from 42,000 to 128,000 ha
with a mean of 73,000 ha. National production of dry cowpea grain also fluctuated between 9,000 and
70,000 tons with a mean of 27,000 tons during these years. The major areas of cultivation are the
regions of Louga (48%), Diourbel(25%) and Thies (20%) in the peanut basin. Cowpea is an important
rainfed trop in the Louga Region. It has greater adaptation to drought than the ot.her available rainfed
crops, Pearl millet, and peanut, which have beem severely damaged by drought in most years since
1968. Within these regions substantial areas of cowpea are cultivated in the departments of Louga
(22%), Kebemer (17%), Mbacke (14%) and Tivaouane (12%). Small areas of cowpea are cultivated in
the River Region (5%), and eastern Senegal and low Casamance (2%).
Cowpea is mainly grown to produce dry grains but, during the “hungry period” in August and
September, substantial quantities (about 25% of total production) are consumed on the farm or
marketed as a fresh vegetable called “green pods” which is equivalent to “southem peas” in the United
States. The grains and fresh peas have a high protein content (about 25% on a dry weight basis), and
an a’mino acid profile that complements the prote:in in rice, millet, maize or whea.t. A combination of
75% cereal and 25% cowpea, on a dry weight basis, provides suffrcient protein for adults if sufficient
grain is eaten to satisfy calorie requirements. Children and mothers require more protein in their diets.
Cowpea hay is an effective feed for livestock in the dry season since it has a higher protein content
thar grass hay.
Scientifïc studies of cowpea in Senegal were initiated in the 1950’s at CNRA, Bambey. A
gerrnplasm collection was developed based upon cowpea accessions collected throughout Senegal and
obtsined from other African countries. The collection is divided into early cowpea accessions, which
flower before late September when sown at the beginning of the rainy season (about July) at Bambey,
and cowpea accessions whose flowering is delayed by long days, such that they flower alter September
when sown in July at Bambey. The early accessions are suitable for production of pods during the
rainy season, whereas the late accessions only are suitable for hay production or relay cropping with
Pearl millet. Agronomie and breeding studies resulted in the development of a set of adapted varieties
and management recommendations by the early 1970’s. Since 1980, ISRA has conducted a program of
cowpea breeding, agronomy, plant pathology, entomology, and socioeconomics with collaborative
assistance from personnel at the Univers@ of California, Riverside through the USAID-funded
BeanlCowpea Collaborative Research Support Program administered by Michigan State University.
This cowpea production bulletin represents a synthesis of the results of the studies conducted prior to
197.5 and since 1980, and is designed to assist scientists, extension personnel and development
agencies working on the improvement of systems for the production and utilization of cowpea in
Africa.
A bulletin written in French also is available from ISBA. Examples are presented of
agricultural chemicals that have been used on cowpea production in Senegal.
N o specific
reccmmendations are made concerning the use of agricultural chemicals and a11 such use must follow
a11 regulations of the Government of Senegal and a11 recommendations of the manufacturer.
2
RAINFA.LL AND SOIL CONDITIONS
Water Reauirements
Cowpea is well-adapted to hot, semiarid climatic zones. Since 1968 there has been a drought in
the northern peanut basin of Senegal with annual rainfall being only 63% (at Louga) and 70% (at
Bambey) of the averages from 1918 to 1967. During the dry period from 196894, the average
rainfalls at Bambey and Louga were 473 and 283 mrn/year, respectively. The water requirements for
maximum yields of a 75-day (period from planting to maturity) cowpea variety were estimated to be
370 and 430 mm at Bambey and Louga, respectively. Consequently, in most years there has been
suffïcient rainfall at Bambey to meet the maximal water requirements of a 75-day or even a 90-day
cowpea variety. At Louga, in contrast, there has not been enough rainfall since 1968 to provide the
maximal water requirements of a 75-day cowpea cultivar. However, certain new varieties with a cycle
length of 60 to 64 days (such as CB5, Barnbey 21, and Melakh) have produced yields as high as 1
tonlha in the Louga Region in years with only 200 mm of rain when crops of Pearl millet and peanut
produced very little food. Cowpea is extremely sensitive to excess water and must be grown in areas
where it is not flooded for extended perifods.
Soi1 Reauirements
Sandy soils (Dior and Dior - Deck) with free drainage are suitable for cowpea production. These
soils provide good aeration which is essential for cowpea root function and plant growth, and cari be
rapidly prepared for sowing by manual or animal-draft harrowing.
VARIETIES
In the main cowpea production zone in the northern and tenter-north areas of the peanut basin the
following varieties have been recornrne:nded: 58-57, Ndiarnbour, Mougne, Barnbey 21, and CB5. In
addition, two new varieties were released, Mouride in 1992 and Melakh in 1993. Each of these
varieties has specifïc characteristics whi.ch make them usefùl in specifïc areas of the main production
zone and specifïc environmental conditions (refer to Table 1 for the agronomie descriptions of these
varieties).
Several local varieties are grown b:y farmers in the main cowpea production zone. Ndiaga Aw,
and Patate have large brown seed and are grown in the departments of Tivaouane and Kebemer.
Marne
Farna has large white seed with a black eye. Ndout, which is very photoperiod sensitive, and Baye
Ngagne have large seed with grey-blue speckles and a cream colored background, and are grown in the
departments of Thies and Barnbey.
In low Casamance and the eastern region variety 59-9 is recomrnended, and some late maturing
local varieties are grown by farmers. The local variety Matam is grown on the edges of the Senegal
River as the flood water retreats.
Two forage varieties are available, 58-74 and 66-35, but they only were used to a limited extent
by farrners up to the date when this bulletin was written in 1996.
3
Tabie i. Cowpea varieiies ÂvaiIabie for lise in Senegai
Seed Characteristics
Origin & Year
Days to
Plant
Resistances to
Name
of Introduction
Weight(mg)
Color
Maturity
Habit
Biotic Stresses
5 8 - 5 7
Landrace 1962
120
Cream with dark
75
spreading
Bacterial Blight
brown eye
Ndiambour
C N R A 1 9 6 9
160
Crearn with light
75
spreading
Bacterial Blight
brown eye
Mougne
CNFL4 1969
150
Grey speckles
75
spreading
Bacterial Blight
on cream
Bambey 21
C N R A 1 9 7 5
180
White
62
erect
Mosaic Virus*
P
CB5
Univ. Calif.
200
White with
60
erect
Mosaic Virus*
1941
black eye
Mouride
CNRAICRSP
160
Cream with light
6 6
semi-erect
Bacterial Blight,
1992
brown eye
Mosaic Virus*,
Striga, and Cowpea
Weevil
Melakh
CNRAKRSP
190
White with
6 4
erect
Bacterial Blight,
1993
brown eye
Mosaic Virus*, and
Cowpea Aphid
*Common strains of cowpea aphid-borne mosaic virus.
CULTURAL METHODS
Cronniw Svstems
More than 95% of cowpea production in Senegal is from sole-crops. In the northern and center-
north areas early to medium-cycle cowpea varieties are grown as sole-crops in annual rotation with
Pearl millet and peanut.
Some relay intercropping of cowpea with Pearl millet occurs in the
departments of Bambey and Thies. For relay intercropping, photoperiod-sensitive varieties of cowpea
are sown into Pearl millet fïelds in mid-August and, if there is sufficient rain, are ready for harvest by
mid-November. In most years since 11968, there has been insufficient rain for relay-intercropped
cowpeas in the departments of Bambey and Thies. Some cowpea is grown along the edges of the
Senegal River using the decrue system. In this system, seed is planted as the flood water recedes and
the plants grow on stored soi1 moisture during the 8cool and dry season from November through March.
In low Casamance, long-cycle cowpea varieties are grown.
Crop management methods are described for sole-cropping in the main production zone in the
northem and tenter-north areas of the peanut basin.
Land Preparation
In most cases land is prepared for sowing at the beginning of the rainy season by manual or
animal-draft harrowing. Much of the soil in the tenter-north area cari develop high bulk densities, and
it would be advantageous to plow the land at the beginning of the rainy season because this results in
stronger root growth and higher yields o,f cowpea, Pearl millet or peanut. However, most farmers do
not have the plows, draft animals or tractors to enable them to plow the land in suffcient time, at the
beginning of the season, SO that they alslo cari plant early. An alternative approach would be to plow
the land just after the harvest, at the end of the rainy season, but this only is effective if there is
sufficient moisture in the soil. Where trop residues or manure are available they would be most
effective in improving soi1 fertility and structure if they are incorporated by plowing.
Useful
production of cowpea cari be achieved if plowing i:; not possible and only harrowing is used to prepare
the land.
Fertilization
One thousand kg of dry cowpea grain contain the equivalent of 50 kg of nitrogen (N), 17 kg of
phosphate (P2O5) and 17 kg of potassium oxide (K20). The whole plant including seed, foliage and
roots could contain double these amounts.
Cowpea cari fix substantial quantities of atmospheric
nitrogen in the root nodules formed in association with rhizobia, which are soil-borne bacteria. Al1 of
cowpea needs for nitrogen could be met by nitrogen fixation; unfortunately, this process only begins to
become active about three weeks after planting. Consequently, in soils that are very infertile it has
been recomrnended that an application of 9 kg N/ha be made just prior to planting. Cowpea roots also
form associations with mycorrhizae, which are soi1 fungi. These associations help the cowpea to take
up P205, zinc and copper from infertile soils. These associations also take about three weeks to
become established and a pre-sowing application of 30 kg F’205/ha with 15 kg K20/ha ha.s been
recommended for infertile soils.
A commercial fertilizer is available in Senegal with N:P205:K20 of 6-20-l 0. The amount of this
fer,tilizer that has been recommended for cowpea grown in infertile soi1 is 150 kg/ha. The fertilizer
should be applied aust before sowing and should be incorporated to a depth of at least 10 cm by
harrowing.
Cowpea does not need fertilizer if the soi1 is at least moderately fertile, and any available
commercial fertilizer or manure should be applied to the Pearl millet trop in the rotation. Pearl millet
has greater needs for nitrogen and is more responsive to fertilizer and manure than cowpea. Pearl
millet grown the year following a cowpea trop Will benefit from the improved soi1 nutrient conditions
re!;ulting from the rhizobial and mycorrhizal a.ssociations with the root system of the cowpea. An
efj’ective annual rotation consists of cowpea, Pearl millet, peanut, Pearl millet, cowpea, etc., with 50%
of the cultivated area for Pearl millet, 25% for peanut, and 25% for cowpea.
Cowpea is mainly sown into wet soi1 at the beginning of the rainy season, after a rain of at least 15
mm. Since 1968, sowing often has occurred in July in the northern and tenter-north areas. Cowpea
should be sown as soon as the soi1 is wet enough to establish the trop because it has substantial
drought resistance during the vegetative stage but needs substantial supplies of water during early
flowering and early pod development. Early sowing enables the trop to escape the late-season
droughts which often occur.
Sowing is done by hand with two or three seeds per planting hole or, preferably, with a peanut
seeder having a disk with 8 holes of a size that Will deliver one or two seeds per hole. For maximum
yields, row spacing of 50 cm is recommende:d with 50 cm between planting holes for the more
sprmeading varieties: 58-57, Mougne and Ndiambour; and 25 cm between plants for the more erect
va:ieties: Bambey 21, CB5, Mouride, and Melakh. The 8 hole disk delivers seed every 33 cm. The
amount of seed required is about 10 to 30 kg/ha depending upon the spacing and the variety. In
circumstances where seed supplies are limited, cowpea should be planted at wide spacing. For the
more spreading varieties the maximum spacing that should be used is 75 cm x 75 cm with two seeds
pe: planting hole which requires only 5 to 7 kg/ha. For the more erect varieties the maximum spacing
recommended is 50 cm x 50 cm with two seeds per planting hole which requires 12 to 16 kg/ha. Plant
errergence and survival cari be enhanced if a chlemical seed treatment is used. One treatment that has
bec:n used is Granox (containing 10% each of captafol, benomyl and furadan). Chemical seed
treatments cari be toxic to humans and must be applied carefully using protective gloves and face
masks, and treated seed must not be eaten.
Weedinz
Weeds should be controlled early to prevent them fi-om either growing ta11 and shading the
coyapeas or depleting soi1 moisture and nutrients. About two weeks alter the cowpeas emerge any
weeds should be killed with a push hoe or an animal-draft cultivator. This weeding should be repeated
about two weeks later. Weeding is most effective if it is followed by dry weather which facilitates the
death of the weeds. If the parasitic weed Striga gesnerioides is present in the fïelds the only effective
control method is to use the resistant cowpea variety Mouride. If any Striga plants emerge they should
be pulled up by hand, removing their roots, and this should be done prior ta flowering to prevent
6
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propagation of Striga seeds. If Striga hermonthica is present in a fïeld, it cari damage Pearl millet and
sorghum, but not cowpea. Growing cowpea in this field may cause suicida1 germination of the seeds
of Striga hermonthica and provide some protection to the following Pearl millet or sorghum crops.
Disease Control
The major disease problems of cowpea in the tenter-north and northem areas of Senegal result
from infection with two seed-borne organisms: bacterial blight (Xanthomonas campestris pv vignicola)
and cowpea aphid-borne mosaic virus, which cari substantially reduce yield.
Bacterial blight is transmitted from infected seedlings to adjacent plants by rain drops and causes
chlorotic patches (orange with a yellow halo) and necrotic patches on the leaves. The pathogen also
cari cause cracking and tankers on the stem and peduncles. The only control is to use varieties with
resistance to bacterial blight, such as Mouride, Melakh, Mougne, Ndiambour and 58-57. Bambey 21
and CB.5 are very susceptible to bacterial blight and seed fïelds of these varieties must not have
significant infection with bacterial blight.
Cowpea aphid-borne mosaic virus is transmitted by cowpea aphids (Aphis craccivora) and causes
distortion and mottling of the leaves and cari stunt the plants. The only control is to use varieties with
resistance to cowpea aphid-borne mosaic virus, such as Mouride, Melalch, Bambey 21 and CB5.
Recent research indicates that some virulent strains of cowpea aphid-borne mosaic virus are present in
Senegal which cause mosaic symptoms on cowpea, a11 varieties are susceptible to the disease, and it is
seed-borne. Several other mosaic viruses are present in Senegal which cari cause leaf mottling
symptoms in these varieties, including southem bean mosaic, cowpea severe mosaic, and cowpea
mottle virus, but these other viruses are net widely distributed. Fields used for seed should not have
significant infection with mosaic viruses, especially variety 58-57 which is very susceptible to cowpea
aphid-borne mosaic virus.
Charcoal rot (Macrophomina phaseolina) cari cause substantial dan-rage to cowpea when soils
became dry and hot. The only potential solution to this problem, at this time, is to grow Pearl millet for
one or more years in infested soils because recent research indicates that this cari reduce the levels of
the sclerotia of the disease organism in the: soil.
In wet conditions Choanephora species cari infect green pods at the point where petals remain
attached to Young pods resulting in a black wet pod rot. The only solutions to this problem are to sow
later or use varieties which flower later so that flowering does not coincide with periods of intense
rainfall. This problem mainly occurs in wet locations and seasons.
When pods become crisp they become susceptible to min damage which causes molds to
proliferate in the pod walls and grains. The solution to this prolblem is to harvest pods as soon as they
are crisp, dry them under the sun, and then thresh the pods and put the grain in a place where they Will
not be damaged by rain. Variety CB5 is very susceptible to this type of dry pod rot.
7
bect Pest Control
T’he major insect pest at the beginning of the growing season is hairy caterpillar (Anzsacta
mo.‘oneyi). The occurrence of hairy caterpillar is sporadic but it cari be particularly damaging in the
dricr part of the cowpea production zone in Louga Region. Waves of hairy caterpillar cari completely
destroy fïelds of cowpea seedlings by eating their leaves. If the wave of hairy caterpillar is late the
cowpea plants may bave sufficient vigor and leaf production to out-grow and survive the attack. The
on1 y control method, at this time, is to spray a. contact insecticide on the hairy caterpillar when it
attacks cowpea seedlings (Thymu135 which cont,ains endosulfan has been used for this purpose).
Cowpea aphids (Aphis craccivora) cari cause problems at any time in the growing season but are
mo,;t damaging when they infest seedlings during dry weather. Cowpea aphids feed on the phloem and
are particularly damaging to Young growing points causing plants to be stunted and they also transmit
viral mosaic diseases. Strong genetic resistance to cowpea aphid is available but, to date, it has only
been incorporated into the new variety, Melakh. When other varieties are used it is necessary to rely
on natural biological control or if the plants are Young or heavily infested to use sprays of insecticides
(Dimethoate and Thymu135 have been used for this purpose).
In the wetter part of the cowpea production zone (south of Bambey) the most damaging insect
pes: is the flower thrip (Megalurothrips sjostedti). These are small shiny black insects that are most
readily observed in flowers. They cari cause substantial damage, however, before flowers are produced
by feeding on floral buds. Strong genetic resistance to flower thrips is not yet available. The
resistance to flower thrips in TVx 3236 and other IITA materials, that are available at this date, is not
sufficiently strong to protect cowpea against the flower thrips present in wetter parts of Senegal. The
new variety Melakh may have moderate resistance to flower thrips. Where flower thrips are present an
insecticide spray cari be applied when the plants begin to produce floral buds, and are showing feeding
damage on the stipules (Decis has been used for this purpose, and contains deltamethrine). A second
sprlly may be applied 7 to 10 days later if there are 9 or more adult thrips per flower. For the major
coMpea production zone north of Bambey, use of insecticides to control flower thrips often is not
nea:ssa.ry but cari increase grain yield in some cases.
Where insecticides are used, extreme tare must be taken in a11 phases of the operation including
disr osa1 of containers, and a11 regulations of the Government of Senegal and a11 recommendations of
the manufacturer must be followed.
Pods should be harvested as soon as they become crisp. Pods usually are harvested by hand,
without pulling up the plant, to provide additional opportunities for the plant to produce pods. Early
erect varieties may only require one harvest, whereas, indeterminate and spreading varieties may
procluce several flushes of pods. Pods uswally are dried in the sun to facilitate threshing, and
winnowing, which also are done manually.
Dry pods must be protected against rain or they Will
develop pod molds which cari totally destroy the grain.
8
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Storape Methods
Cowpea storage weevil eats cowpea grain making distinctive round holes. Damage is apparent
about 2 to 3 months after harvest and virtually a11 of the grains may have holes by 6 months.
Consumers have a strong aversion to grain that has been damaged by weevils, but it still cari be
effective as seed; although, germination percentage may have been reduced.
Protective methods must be used if grain is to be stored longer than 2 months. Adult beetles lay
eggs on the pods and grain both in the fïeld and after threshlng.
The eggs hatch and the larvae bore
into the grains and complete their development within them. Adults emerge from the grain through the
characteristic round exit holes made by the larvae. The adults mate and then lay about 50 eggs on
other grains and the cycle begins aga:in.
An individual life cycle is completed in 3 to 4 weeks.
Consequently, from a modest initial infestation many of the grains may have either weevil eggs on
them or holes within them after two months in storage and two cycles of weevil reproduction.
Several methods of protection are available. After threshing, grain cari be disinfested. The most
practical method for farmers is to use a solar he:ater. Late in the mon-ring of a surmy day, a black
plastic sheet is placed on a layer of dry grass, which reduces, transfer of heat into the soil. A layer of
grains are placed on the black plastic and this layer of grains is covered by a transparent plastic sheet
which is held in place with logs or bricks. Within four hours the grain Will become hot enough (57 to
70°C) to kil1 a11 stages of the cowpea weevil without harming the germination capability of the seed.
The grain should be removed from the solar h.eater in the late aftemoon of the same day. An
alternative method is to fùmigate cowpea grain in large plastic bags using phostoxin but this must be
done carefully because a short exposure ta phostoxin gas cari kil1 people.
After disinfestation or even without disinfestation, grain cari be stored in air-tight containers
consisting of metal drums. These containers not only prevent re-infestation but they also cari kil1 a11
stages of the weevil present on or in the grain if they are kept closed for at least 2 months. During this
period, respiration by the seed and any insects that are present reduces the oxygen concentration and
increases the carbon dioxide concentration to levels that kil1 the weevils but do not harm the
germination capability of the seed. An alternative method, for storing small quantities for use as seed
the following year, consists of mixing grain with. an equal volume of ash, which bas been sieved to
remove wood and other large particles, placing the mixture into a clay pot, and then covering the top
with a layer of ash. Another method has been used where large quantities of cowpea grain are to be
stored in sacks. This consists of using the insecticidal powder K-othrine which must be thoroughly
mixed with the grain.
Any use of phostoxin and K-othrine must follow a11 regulations of the
Govemment of Senegal and a11 recommendations of the manufacturer. One new variety of cowpea,
Mouride, has a moderate level of genetic resistance which reduces damage caused by cowpea weevil
but it is still necessary to use other protective measures when grain of this variety is to be stored more
than two months.
JYlarketinz
There is a fiee market for cowpea in Senegal.
Prices for dry grain are lowest just after the
harvesting of the main trop in October, but they progressivelly increase and cari attain high levels by
July. Varieties with large white or cream seed are preferred for export and making processed foods,
9
which require cowpea flour or grits, and are suitable for most uses. Local varieties with brown seed are
preferred in some local dishes because of their flavor and the color they impart to the food.
During
August and September, relatively high prices cari be obtained for cowpea as a fresh vegetable called
“g,:een pods” which are about double the prices received for dry grain. The varieties most suitable for
us: as green pods are Melakh, Bambey 21, and CB.5 because they produce pods early, when the price is
high, and have good pod and seed quality. Fresh cowpeas sometimes are shelled and placed in plastic
bags for sale. Cowpeas keep fresh for a longer period, however, if left in the pods, and a con-mon
coDking method is to boil the pods and then people shell the pods just prior to eating the cowpeas.
Prces for cowpea for use as seed cari be high in June, but the seed must have a high germination
percentage and it must be pure and not contain seed of other varieties. Ideally, seed shou’ld be
produced in large fïelds to reduce contamination by cross pollination or seed mixing during harvest.
There should not be significant levels of bacterial blight or cowpea aphid-borne mosaic virus in fïelds
used for seed because these diseases would infect the next trop.
10
i
ACKNOWLEDGEMENTS
This bulletin is based on the work of the following scientists from ISRA and other organizations as
noted.
Agronomists
Claude Dancette
Madiagne Diagne
Mamadou Ndiaye
Samba Thiaw
Moctar Wade
Breeders
Djibril Sène
Ndiaga Cisse
Entomologists
Mbaye Ndoye
Amadou Bocar Bal
Dogo Seck
Larry Murdock, Purdue University
Georges Ntoukam, IRA, Cameron
Laurie W. Kitch, Purdue Univers@
Mamadou Balde
Plant Pathologists
D. G. Gaikwad
Mbaye Ndiaye
Socioeconomist
Mbene Dieye Faye
Scientifk Advisors
Anthony E. Hall, Univers@ of Califbrnia, Riverside
Prabodh N. Patel, University of Califfornia, Riverside
Richard 0. Hampton, USDA and Oregon State University
Jeffi-ey D. Ehlers, Univers@ of California, Riverside
Financial support was provided by the Govemment of Senegal and the BeanKowpea Collaborative
Research Support Program of USAID, Grant No. DAN-1310-G-SS-6008-00. The opinions and
recommendations are those of the authors and not necessarily those of USAID, whose fùnding of this
work is gratefully acknowledged.
11
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I
fii$!
I S R A
DRCSP
Institut Sénégalais
Direction des Recherches sur les
de Recherches Agricoles
Cultures et Systèmes Pluviaux
COWPEA PRODUCTION BULLETIN FOR SENEGAL
Anthony E. Hall”, Ndiaga Cisse, Samba Thiaw,
Mbaye Ndiaye, Mbene Dieye Paye, and Mamadou Balde
1
CNRA
Centre National de Recherches
Agronomiques de Bambey
Bambey BP53
SIENEGAL
*Dep,artment of Botany and Plant Sciences
University of California
Riverside, CA 92521-0124, U.S.A.
1996
F&IA
INTRODUCTION
W%
Cowpea (Signa unguiculata (L.) Walp.) was domesticated in West Africa and has been cultivated
there for thousands of years. It was distributed to other parts of Africa and other continents by the
migration of people and trade. West Africa still has the major area of cowpea cultivation in the world.
In Senegal the area of cowpea production during 1980 to 1994 varied from 42,000 to 128,000 ha
with a mean of 73,000 ha. National production of dry cowpea grain also fluctuated between 9,000 and
70,000 tons with a mean of 27,000 tons during these years. The major areas of cultivation are the
regions of Louga (48%), Diourbel(25%) and Thies (20%) in the peanut basin. Cowpea is an important
rainfed trop in the Louga Region. It has greater adaptation to drought than the ot.her available rainfed
crops, Pearl millet, and peanut, which have beem severely damaged by drought in most years since
1968. Within these regions substantial areas of cowpea are cultivated in the departments of Louga
(22%), Kebemer (17%), Mbacke (14%) and Tivaouane (12%). Small areas of cowpea are cultivated in
the River Region (5%), and eastern Senegal and low Casamance (2%).
Cowpea is mainly grown to produce dry grains but, during the “hungry period” in August and
September, substantial quantities (about 25% of total production) are consumed on the farm or
marketed as a fresh vegetable called “green pods” which is equivalent to “southem peas” in the United
States. The grains and fresh peas have a high protein content (about 25% on a dry weight basis), and
an a’mino acid profile that complements the prote:in in rice, millet, maize or whea.t. A combination of
75% cereal and 25% cowpea, on a dry weight basis, provides suffrcient protein for adults if sufficient
grain is eaten to satisfy calorie requirements. Children and mothers require more protein in their diets.
Cowpea hay is an effective feed for livestock in the dry season since it has a higher protein content
thar grass hay.
Scientifïc studies of cowpea in Senegal were initiated in the 1950’s at CNRA, Bambey. A
gerrnplasm collection was developed based upon cowpea accessions collected throughout Senegal and
obtsined from other African countries. The collection is divided into early cowpea accessions, which
flower before late September when sown at the beginning of the rainy season (about July) at Bambey,
and cowpea accessions whose flowering is delayed by long days, such that they flower alter September
when sown in July at Bambey. The early accessions are suitable for production of pods during the
rainy season, whereas the late accessions only are suitable for hay production or relay cropping with
Pearl millet. Agronomie and breeding studies resulted in the development of a set of adapted varieties
and management recommendations by the early 1970’s. Since 1980, ISRA has conducted a program of
cowpea breeding, agronomy, plant pathology, entomology, and socioeconomics with collaborative
assistance from personnel at the Univers@ of California, Riverside through the USAID-funded
BeanlCowpea Collaborative Research Support Program administered by Michigan State University.
This cowpea production bulletin represents a synthesis of the results of the studies conducted prior to
197.5 and since 1980, and is designed to assist scientists, extension personnel and development
agencies working on the improvement of systems for the production and utilization of cowpea in
Africa.
A bulletin written in French also is available from ISBA. Examples are presented of
agricultural chemicals that have been used on cowpea production in Senegal.
N o specific
reccmmendations are made concerning the use of agricultural chemicals and a11 such use must follow
a11 regulations of the Government of Senegal and a11 recommendations of the manufacturer.
2
RAINFA.LL AND SOIL CONDITIONS
Water Reauirements
Cowpea is well-adapted to hot, semiarid climatic zones. Since 1968 there has been a drought in
the northern peanut basin of Senegal with annual rainfall being only 63% (at Louga) and 70% (at
Bambey) of the averages from 1918 to 1967. During the dry period from 196894, the average
rainfalls at Bambey and Louga were 473 and 283 mrn/year, respectively. The water requirements for
maximum yields of a 75-day (period from planting to maturity) cowpea variety were estimated to be
370 and 430 mm at Bambey and Louga, respectively. Consequently, in most years there has been
suffïcient rainfall at Bambey to meet the maximal water requirements of a 75-day or even a 90-day
cowpea variety. At Louga, in contrast, there has not been enough rainfall since 1968 to provide the
maximal water requirements of a 75-day cowpea cultivar. However, certain new varieties with a cycle
length of 60 to 64 days (such as CB5, Barnbey 21, and Melakh) have produced yields as high as 1
tonlha in the Louga Region in years with only 200 mm of rain when crops of Pearl millet and peanut
produced very little food. Cowpea is extremely sensitive to excess water and must be grown in areas
where it is not flooded for extended perifods.
Soi1 Reauirements
Sandy soils (Dior and Dior - Deck) with free drainage are suitable for cowpea production. These
soils provide good aeration which is essential for cowpea root function and plant growth, and cari be
rapidly prepared for sowing by manual or animal-draft harrowing.
VARIETIES
In the main cowpea production zone in the northern and tenter-north areas of the peanut basin the
following varieties have been recornrne:nded: 58-57, Ndiarnbour, Mougne, Barnbey 21, and CB5. In
addition, two new varieties were released, Mouride in 1992 and Melakh in 1993. Each of these
varieties has specifïc characteristics whi.ch make them usefùl in specifïc areas of the main production
zone and specifïc environmental conditions (refer to Table 1 for the agronomie descriptions of these
varieties).
Several local varieties are grown b:y farmers in the main cowpea production zone. Ndiaga Aw,
and Patate have large brown seed and are grown in the departments of Tivaouane and Kebemer.
Marne
Farna has large white seed with a black eye. Ndout, which is very photoperiod sensitive, and Baye
Ngagne have large seed with grey-blue speckles and a cream colored background, and are grown in the
departments of Thies and Barnbey.
In low Casamance and the eastern region variety 59-9 is recomrnended, and some late maturing
local varieties are grown by farmers. The local variety Matam is grown on the edges of the Senegal
River as the flood water retreats.
Two forage varieties are available, 58-74 and 66-35, but they only were used to a limited extent
by farrners up to the date when this bulletin was written in 1996.
3
Tabie i. Cowpea varieiies ÂvaiIabie for lise in Senegai
Seed Characteristics
Origin & Year
Days to
Plant
Resistances to
Name
of Introduction
Weight(mg)
Color
Maturity
Habit
Biotic Stresses
5 8 - 5 7
Landrace 1962
120
Cream with dark
75
spreading
Bacterial Blight
brown eye
Ndiambour
C N R A 1 9 6 9
160
Crearn with light
75
spreading
Bacterial Blight
brown eye
Mougne
CNFL4 1969
150
Grey speckles
75
spreading
Bacterial Blight
on cream
Bambey 21
C N R A 1 9 7 5
180
White
62
erect
Mosaic Virus*
P
CB5
Univ. Calif.
200
White with
60
erect
Mosaic Virus*
1941
black eye
Mouride
CNRAICRSP
160
Cream with light
6 6
semi-erect
Bacterial Blight,
1992
brown eye
Mosaic Virus*,
Striga, and Cowpea
Weevil
Melakh
CNRAKRSP
190
White with
6 4
erect
Bacterial Blight,
1993
brown eye
Mosaic Virus*, and
Cowpea Aphid
*Common strains of cowpea aphid-borne mosaic virus.
CULTURAL METHODS
Cronniw Svstems
More than 95% of cowpea production in Senegal is from sole-crops. In the northern and center-
north areas early to medium-cycle cowpea varieties are grown as sole-crops in annual rotation with
Pearl millet and peanut.
Some relay intercropping of cowpea with Pearl millet occurs in the
departments of Bambey and Thies. For relay intercropping, photoperiod-sensitive varieties of cowpea
are sown into Pearl millet fïelds in mid-August and, if there is sufficient rain, are ready for harvest by
mid-November. In most years since 11968, there has been insufficient rain for relay-intercropped
cowpeas in the departments of Bambey and Thies. Some cowpea is grown along the edges of the
Senegal River using the decrue system. In this system, seed is planted as the flood water recedes and
the plants grow on stored soi1 moisture during the 8cool and dry season from November through March.
In low Casamance, long-cycle cowpea varieties are grown.
Crop management methods are described for sole-cropping in the main production zone in the
northem and tenter-north areas of the peanut basin.
Land Preparation
In most cases land is prepared for sowing at the beginning of the rainy season by manual or
animal-draft harrowing. Much of the soil in the tenter-north area cari develop high bulk densities, and
it would be advantageous to plow the land at the beginning of the rainy season because this results in
stronger root growth and higher yields o,f cowpea, Pearl millet or peanut. However, most farmers do
not have the plows, draft animals or tractors to enable them to plow the land in suffcient time, at the
beginning of the season, SO that they alslo cari plant early. An alternative approach would be to plow
the land just after the harvest, at the end of the rainy season, but this only is effective if there is
sufficient moisture in the soil. Where trop residues or manure are available they would be most
effective in improving soi1 fertility and structure if they are incorporated by plowing.
Useful
production of cowpea cari be achieved if plowing i:; not possible and only harrowing is used to prepare
the land.
Fertilization
One thousand kg of dry cowpea grain contain the equivalent of 50 kg of nitrogen (N), 17 kg of
phosphate (P2O5) and 17 kg of potassium oxide (K20). The whole plant including seed, foliage and
roots could contain double these amounts.
Cowpea cari fix substantial quantities of atmospheric
nitrogen in the root nodules formed in association with rhizobia, which are soil-borne bacteria. Al1 of
cowpea needs for nitrogen could be met by nitrogen fixation; unfortunately, this process only begins to
become active about three weeks after planting. Consequently, in soils that are very infertile it has
been recomrnended that an application of 9 kg N/ha be made just prior to planting. Cowpea roots also
form associations with mycorrhizae, which are soi1 fungi. These associations help the cowpea to take
up P205, zinc and copper from infertile soils. These associations also take about three weeks to
become established and a pre-sowing application of 30 kg F’205/ha with 15 kg K20/ha ha.s been
recommended for infertile soils.
A commercial fertilizer is available in Senegal with N:P205:K20 of 6-20-l 0. The amount of this
fer,tilizer that has been recommended for cowpea grown in infertile soi1 is 150 kg/ha. The fertilizer
should be applied aust before sowing and should be incorporated to a depth of at least 10 cm by
harrowing.
Cowpea does not need fertilizer if the soi1 is at least moderately fertile, and any available
commercial fertilizer or manure should be applied to the Pearl millet trop in the rotation. Pearl millet
has greater needs for nitrogen and is more responsive to fertilizer and manure than cowpea. Pearl
millet grown the year following a cowpea trop Will benefit from the improved soi1 nutrient conditions
re!;ulting from the rhizobial and mycorrhizal a.ssociations with the root system of the cowpea. An
efj’ective annual rotation consists of cowpea, Pearl millet, peanut, Pearl millet, cowpea, etc., with 50%
of the cultivated area for Pearl millet, 25% for peanut, and 25% for cowpea.
Cowpea is mainly sown into wet soi1 at the beginning of the rainy season, after a rain of at least 15
mm. Since 1968, sowing often has occurred in July in the northern and tenter-north areas. Cowpea
should be sown as soon as the soi1 is wet enough to establish the trop because it has substantial
drought resistance during the vegetative stage but needs substantial supplies of water during early
flowering and early pod development. Early sowing enables the trop to escape the late-season
droughts which often occur.
Sowing is done by hand with two or three seeds per planting hole or, preferably, with a peanut
seeder having a disk with 8 holes of a size that Will deliver one or two seeds per hole. For maximum
yields, row spacing of 50 cm is recommende:d with 50 cm between planting holes for the more
sprmeading varieties: 58-57, Mougne and Ndiambour; and 25 cm between plants for the more erect
va:ieties: Bambey 21, CB5, Mouride, and Melakh. The 8 hole disk delivers seed every 33 cm. The
amount of seed required is about 10 to 30 kg/ha depending upon the spacing and the variety. In
circumstances where seed supplies are limited, cowpea should be planted at wide spacing. For the
more spreading varieties the maximum spacing that should be used is 75 cm x 75 cm with two seeds
pe: planting hole which requires only 5 to 7 kg/ha. For the more erect varieties the maximum spacing
recommended is 50 cm x 50 cm with two seeds per planting hole which requires 12 to 16 kg/ha. Plant
errergence and survival cari be enhanced if a chlemical seed treatment is used. One treatment that has
bec:n used is Granox (containing 10% each of captafol, benomyl and furadan). Chemical seed
treatments cari be toxic to humans and must be applied carefully using protective gloves and face
masks, and treated seed must not be eaten.
Weedinz
Weeds should be controlled early to prevent them fi-om either growing ta11 and shading the
coyapeas or depleting soi1 moisture and nutrients. About two weeks alter the cowpeas emerge any
weeds should be killed with a push hoe or an animal-draft cultivator. This weeding should be repeated
about two weeks later. Weeding is most effective if it is followed by dry weather which facilitates the
death of the weeds. If the parasitic weed Striga gesnerioides is present in the fïelds the only effective
control method is to use the resistant cowpea variety Mouride. If any Striga plants emerge they should
be pulled up by hand, removing their roots, and this should be done prior ta flowering to prevent
6
-..
-.----.
propagation of Striga seeds. If Striga hermonthica is present in a fïeld, it cari damage Pearl millet and
sorghum, but not cowpea. Growing cowpea in this field may cause suicida1 germination of the seeds
of Striga hermonthica and provide some protection to the following Pearl millet or sorghum crops.
Disease Control
The major disease problems of cowpea in the tenter-north and northem areas of Senegal result
from infection with two seed-borne organisms: bacterial blight (Xanthomonas campestris pv vignicola)
and cowpea aphid-borne mosaic virus, which cari substantially reduce yield.
Bacterial blight is transmitted from infected seedlings to adjacent plants by rain drops and causes
chlorotic patches (orange with a yellow halo) and necrotic patches on the leaves. The pathogen also
cari cause cracking and tankers on the stem and peduncles. The only control is to use varieties with
resistance to bacterial blight, such as Mouride, Melakh, Mougne, Ndiambour and 58-57. Bambey 21
and CB.5 are very susceptible to bacterial blight and seed fïelds of these varieties must not have
significant infection with bacterial blight.
Cowpea aphid-borne mosaic virus is transmitted by cowpea aphids (Aphis craccivora) and causes
distortion and mottling of the leaves and cari stunt the plants. The only control is to use varieties with
resistance to cowpea aphid-borne mosaic virus, such as Mouride, Melalch, Bambey 21 and CB5.
Recent research indicates that some virulent strains of cowpea aphid-borne mosaic virus are present in
Senegal which cause mosaic symptoms on cowpea, a11 varieties are susceptible to the disease, and it is
seed-borne. Several other mosaic viruses are present in Senegal which cari cause leaf mottling
symptoms in these varieties, including southem bean mosaic, cowpea severe mosaic, and cowpea
mottle virus, but these other viruses are net widely distributed. Fields used for seed should not have
significant infection with mosaic viruses, especially variety 58-57 which is very susceptible to cowpea
aphid-borne mosaic virus.
Charcoal rot (Macrophomina phaseolina) cari cause substantial dan-rage to cowpea when soils
became dry and hot. The only potential solution to this problem, at this time, is to grow Pearl millet for
one or more years in infested soils because recent research indicates that this cari reduce the levels of
the sclerotia of the disease organism in the: soil.
In wet conditions Choanephora species cari infect green pods at the point where petals remain
attached to Young pods resulting in a black wet pod rot. The only solutions to this problem are to sow
later or use varieties which flower later so that flowering does not coincide with periods of intense
rainfall. This problem mainly occurs in wet locations and seasons.
When pods become crisp they become susceptible to min damage which causes molds to
proliferate in the pod walls and grains. The solution to this prolblem is to harvest pods as soon as they
are crisp, dry them under the sun, and then thresh the pods and put the grain in a place where they Will
not be damaged by rain. Variety CB5 is very susceptible to this type of dry pod rot.
7
bect Pest Control
T’he major insect pest at the beginning of the growing season is hairy caterpillar (Anzsacta
mo.‘oneyi). The occurrence of hairy caterpillar is sporadic but it cari be particularly damaging in the
dricr part of the cowpea production zone in Louga Region. Waves of hairy caterpillar cari completely
destroy fïelds of cowpea seedlings by eating their leaves. If the wave of hairy caterpillar is late the
cowpea plants may bave sufficient vigor and leaf production to out-grow and survive the attack. The
on1 y control method, at this time, is to spray a. contact insecticide on the hairy caterpillar when it
attacks cowpea seedlings (Thymu135 which cont,ains endosulfan has been used for this purpose).
Cowpea aphids (Aphis craccivora) cari cause problems at any time in the growing season but are
mo,;t damaging when they infest seedlings during dry weather. Cowpea aphids feed on the phloem and
are particularly damaging to Young growing points causing plants to be stunted and they also transmit
viral mosaic diseases. Strong genetic resistance to cowpea aphid is available but, to date, it has only
been incorporated into the new variety, Melakh. When other varieties are used it is necessary to rely
on natural biological control or if the plants are Young or heavily infested to use sprays of insecticides
(Dimethoate and Thymu135 have been used for this purpose).
In the wetter part of the cowpea production zone (south of Bambey) the most damaging insect
pes: is the flower thrip (Megalurothrips sjostedti). These are small shiny black insects that are most
readily observed in flowers. They cari cause substantial damage, however, before flowers are produced
by feeding on floral buds. Strong genetic resistance to flower thrips is not yet available. The
resistance to flower thrips in TVx 3236 and other IITA materials, that are available at this date, is not
sufficiently strong to protect cowpea against the flower thrips present in wetter parts of Senegal. The
new variety Melakh may have moderate resistance to flower thrips. Where flower thrips are present an
insecticide spray cari be applied when the plants begin to produce floral buds, and are showing feeding
damage on the stipules (Decis has been used for this purpose, and contains deltamethrine). A second
sprlly may be applied 7 to 10 days later if there are 9 or more adult thrips per flower. For the major
coMpea production zone north of Bambey, use of insecticides to control flower thrips often is not
nea:ssa.ry but cari increase grain yield in some cases.
Where insecticides are used, extreme tare must be taken in a11 phases of the operation including
disr osa1 of containers, and a11 regulations of the Government of Senegal and a11 recommendations of
the manufacturer must be followed.
Pods should be harvested as soon as they become crisp. Pods usually are harvested by hand,
without pulling up the plant, to provide additional opportunities for the plant to produce pods. Early
erect varieties may only require one harvest, whereas, indeterminate and spreading varieties may
procluce several flushes of pods. Pods uswally are dried in the sun to facilitate threshing, and
winnowing, which also are done manually.
Dry pods must be protected against rain or they Will
develop pod molds which cari totally destroy the grain.
8
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Storape Methods
Cowpea storage weevil eats cowpea grain making distinctive round holes. Damage is apparent
about 2 to 3 months after harvest and virtually a11 of the grains may have holes by 6 months.
Consumers have a strong aversion to grain that has been damaged by weevils, but it still cari be
effective as seed; although, germination percentage may have been reduced.
Protective methods must be used if grain is to be stored longer than 2 months. Adult beetles lay
eggs on the pods and grain both in the fïeld and after threshlng.
The eggs hatch and the larvae bore
into the grains and complete their development within them. Adults emerge from the grain through the
characteristic round exit holes made by the larvae. The adults mate and then lay about 50 eggs on
other grains and the cycle begins aga:in.
An individual life cycle is completed in 3 to 4 weeks.
Consequently, from a modest initial infestation many of the grains may have either weevil eggs on
them or holes within them after two months in storage and two cycles of weevil reproduction.
Several methods of protection are available. After threshing, grain cari be disinfested. The most
practical method for farmers is to use a solar he:ater. Late in the mon-ring of a surmy day, a black
plastic sheet is placed on a layer of dry grass, which reduces, transfer of heat into the soil. A layer of
grains are placed on the black plastic and this layer of grains is covered by a transparent plastic sheet
which is held in place with logs or bricks. Within four hours the grain Will become hot enough (57 to
70°C) to kil1 a11 stages of the cowpea weevil without harming the germination capability of the seed.
The grain should be removed from the solar h.eater in the late aftemoon of the same day. An
alternative method is to fùmigate cowpea grain in large plastic bags using phostoxin but this must be
done carefully because a short exposure ta phostoxin gas cari kil1 people.
After disinfestation or even without disinfestation, grain cari be stored in air-tight containers
consisting of metal drums. These containers not only prevent re-infestation but they also cari kil1 a11
stages of the weevil present on or in the grain if they are kept closed for at least 2 months. During this
period, respiration by the seed and any insects that are present reduces the oxygen concentration and
increases the carbon dioxide concentration to levels that kil1 the weevils but do not harm the
germination capability of the seed. An alternative method, for storing small quantities for use as seed
the following year, consists of mixing grain with. an equal volume of ash, which bas been sieved to
remove wood and other large particles, placing the mixture into a clay pot, and then covering the top
with a layer of ash. Another method has been used where large quantities of cowpea grain are to be
stored in sacks. This consists of using the insecticidal powder K-othrine which must be thoroughly
mixed with the grain.
Any use of phostoxin and K-othrine must follow a11 regulations of the
Govemment of Senegal and a11 recommendations of the manufacturer. One new variety of cowpea,
Mouride, has a moderate level of genetic resistance which reduces damage caused by cowpea weevil
but it is still necessary to use other protective measures when grain of this variety is to be stored more
than two months.
JYlarketinz
There is a fiee market for cowpea in Senegal.
Prices for dry grain are lowest just after the
harvesting of the main trop in October, but they progressivelly increase and cari attain high levels by
July. Varieties with large white or cream seed are preferred for export and making processed foods,
9
which require cowpea flour or grits, and are suitable for most uses. Local varieties with brown seed are
preferred in some local dishes because of their flavor and the color they impart to the food.
During
August and September, relatively high prices cari be obtained for cowpea as a fresh vegetable called
“g,:een pods” which are about double the prices received for dry grain. The varieties most suitable for
us: as green pods are Melakh, Bambey 21, and CB.5 because they produce pods early, when the price is
high, and have good pod and seed quality. Fresh cowpeas sometimes are shelled and placed in plastic
bags for sale. Cowpeas keep fresh for a longer period, however, if left in the pods, and a con-mon
coDking method is to boil the pods and then people shell the pods just prior to eating the cowpeas.
Prces for cowpea for use as seed cari be high in June, but the seed must have a high germination
percentage and it must be pure and not contain seed of other varieties. Ideally, seed shou’ld be
produced in large fïelds to reduce contamination by cross pollination or seed mixing during harvest.
There should not be significant levels of bacterial blight or cowpea aphid-borne mosaic virus in fïelds
used for seed because these diseases would infect the next trop.
10
i
ACKNOWLEDGEMENTS
This bulletin is based on the work of the following scientists from ISRA and other organizations as
noted.
Agronomists
Claude Dancette
Madiagne Diagne
Mamadou Ndiaye
Samba Thiaw
Moctar Wade
Breeders
Djibril Sène
Ndiaga Cisse
Entomologists
Mbaye Ndoye
Amadou Bocar Bal
Dogo Seck
Larry Murdock, Purdue University
Georges Ntoukam, IRA, Cameron
Laurie W. Kitch, Purdue Univers@
Mamadou Balde
Plant Pathologists
D. G. Gaikwad
Mbaye Ndiaye
Socioeconomist
Mbene Dieye Faye
Scientifk Advisors
Anthony E. Hall, Univers@ of Califbrnia, Riverside
Prabodh N. Patel, University of Califfornia, Riverside
Richard 0. Hampton, USDA and Oregon State University
Jeffi-ey D. Ehlers, Univers@ of California, Riverside
Financial support was provided by the Govemment of Senegal and the BeanKowpea Collaborative
Research Support Program of USAID, Grant No. DAN-1310-G-SS-6008-00. The opinions and
recommendations are those of the authors and not necessarily those of USAID, whose fùnding of this
work is gratefully acknowledged.
11