Pest Management in North West
Africa
Foreword:
This webpage is designed to give a small introduction to the
background of pest and their management in northern and western
Africa. The most common diseases and pests are listed, however
this page can be most useful as a starting point for more specific
questions.
This site was created by:
Table of Contents
Staple Crops 
Maize Borer
Cassava Mealy Bug
Useful publications:
Pyralidae spp.
Bean Pod-borers
Staple Crops
Between 20 - 40% of the worlds food supply is lost during
production and post-production to insect pests. Maize and sorghum
are important staple crops for millions of people in east and
southern Africa. Food security is under considerable threat from
a lot of groups of insect pests.
young women
carrying maize home
sorghum
just before harvest
Maize Borer
In a lot of parts in North West Africa pests attacking maize
are a big problem. Especially the Maize Borer can develope big
populations and destroy half of the yield in one year. Stemborers,
the larval stage of certain
kinds of moth, cause losses in maize running into the millions
of tonnes annually, enough to feed more than seven and a half
million people
in the region for a year. Losses caused by stemborers in these
two grains are typically in the neighborhood of 20–40% of
the potential
yield. The pests are particularly difficult to control by conventional
means because the damaging larvae are hidden away deep inside
the plant
stems. Over the past 5 years,The International Centre of Insect
Physiology and Ecology (ICIPE)
(sometimes this link does not work) has
specialized in developing methods for managing these devastating
insects by avoid the use of environmentally damaging and expensive
synthetic insecticides. The Plant
Pathology Department of the University of Hannover, Germany
worked together with this institution and had several projects
in Benin, to search for biocontrols for this insect.
a picture of the maize stemborer
Cassava Mealy Bug
Other important crops in this region are cassava and millet.
The two crops are also threaten by pests.
cassave is mostly processed in
the villages
here: women and younger kids help to peel the tubers
for further food preparation
Cassava is an introduced crop from South America but it is
now well established in Africa.
millet harvest
The most severe one is the cassava mealy bug. Its larvae feeds
on all kinds of sweet potato and can destroy the total yield of
one year. As for most of the insect pests, plant pathology agencies
try to find a natural enemy for these pests. The International
Institute of Tropical Agriculture (IITA)
launched a search for the natural enemy in South America in 1980.
It was found that the most successful biological
agent against mealybugs is a parasitic wasp (Epidinocarsis Lopezi).
mealybugs attacking
cassava leaves
the antagonist of the mealy bug :a small wasp
Here are some useful
publications:
Influence of intercropping on the abundance,
distribution and parasitism of Chilo spp. (Lepidoptera: Pyralidae)
eggs. Pats, P., Ekbom, B., Skovgard,H. , 1997, Bulletin
of entomological research. V:87, pp. 507-513.
ABSTRACT: Two of the most common and serious
pests of maize and sorghum in the coastal areas of East Africa
are the pyralid species, Chilo partellus (Swinhoe) and C. orichalcociliellus
(Strand). Maize monocrop (with high and low plant density) and
maize/cowpea mixed intercrop field experiments were conducted
in Kenya to test if intercropping decreased the number of egg
batches laid, altered the distribution of the egg batches and
influenced egg parasitism. There was no significant difference
in the number of egg batches per plant between treatments and
the egg batches were randomly distributed on
and among plants in most of the plots for all three treatments.
There was a tendency for higher egg parasitism in the intercrop.
The proportion of eggs parasitized was significantly correlated
with total number of eggs per plot suggesting a positive density
dependent response. It is concluded that intercropping does not
affect C. partellus nor C. orichalcociliellus oviposition behaviour
but egg parasitism is likely to be augmented.
Effects of intercropping
with maize on the incidence and damage caused by pod borers of
common beans, Karel, A., 1993, Environmental
entomology, v.22, pp. 1076-1083.
ABSTRACTS: Effects of intercropping common
bean, Phaseolus vulgaris L., with maize, Zea mays L., at four
plant populations on the pod borers Maruca testulalis Geyer and
Heliothis armigera Hubner
on common bean were studied. The incidence of M. testulalis and
H. armigera larvae was significantly (P < 0.05) lower in intercropped
and higher plant populations than in pure stands and lower plant
populations of common bean; larval populations of M. testulalis
increased 45-59 d after planting, followed by a decrease up to
66 d after planting. Percentages of damage to flowers and pods
by larvae of the two pod borer species were significantly (P <
0.05) lower in an intercrop combination of one-third bean-two-thirds
maize
(BMM) than in pure bean (BBB). Flower and pod damage decreased
when plant populations increased from 66,666 to 1,333,333 plants
per ha. The relationship of intercrop combinations and individual
plant populations to incidence and damage by pod borer larvae
was established by exponential
and power regression models. Seed yields of intercrop combinations
of BBM and BMM were higher than those of the two crops when grown
in monoculture at 133,333 and 266,666 plants per ha. "Relative
yield total" thus indicated yield advantages of 16-29% for
plant populations of 133,333 plants per ha in both BBM and BMM
intercrop combinations, which was associated with lower incidence
and damage by pod borer species. Intercropping beans with maize
was considered useful as a cultural method for controlling pod
borers on common beans and for higher seed yield of the two crops.
Mechanisms of
alteration in bean rust epidemiology due to intercropping with
maize, Boudreau, M., Mundt, C.,
1992, Phytopathology, V. 82, pp. 1051-1060.
ABSTRACTS: We performed experiments to identify
how maize influences bean rust (caused by Uromyces appendiculatus)
in maize-bean intercrops. The effects of competition with maize
and interference by maize on dispersal of rust urediniospores
were evaluated in trials conducted three times during 1989 and
1990. Alterations in the nondispersal (infection) phase of the
pathogen life cycle due to intercropping and
competition with maize also were assessed. Overall effects of
maize on rust severity were evaluated in another experiment. Competition
consistently steepened dispersal gradients (P < 0.10) in trials
conducted more than 50 days after planting alone or in combination
with interference (intercrop). Interference had no clear effect
on dispersal gradients. Estimated total spore deposition per plot
was increased (second trial) and decreased (third trial) by competition
in both years (P < 0.05). Intercropping only affected infection
once, in late 1989, when rust severity was reduced by 96% (P <
0.05). Overall disease was reduced by intercropping at two plot
locations in both years (P = 0.07), but not at a third location.
Bean leaf area declined because of competition in 1989 but not
in 1990. Steep gradients may be due to increased spore escape,
and microclimatic changes created by maize are probably responsible
for the nondispersal effect.
Effects of plant
populations and intercripping on the population patterns of bean
flies on common beans, Karel, A.,
1991, Environmental entomology, V. 20, pp. 354-357.
ABSTRACTS: Effects of four plant populations
and intercropping beans with maize on the population patterns
of bean flies (Ophiomyia phaseoli Tryon, O. centrosematis de Meijere,
and Melanagromyza spencerella Greathead) on common beans were
studied. Percentage of plants infested by bean Dies was
significantly less in the one-third beans and two-thirds maize
intercrop combination than in pure stand beans. The incidence
of bean flies decreased with increasing plant populations from
66,666 to 533,332 plants per ha. Ovipunctures made by bean flies
in the leaves of beans were not significantly different among
the various treatments. A significant and gradual decrease in
the number of ovipunctures from lower to higher plant populations
was recorded. The bean fly larva-pupal counts were significantly
lower in both intercrop combinations than in pure stand beans;
larval-pupal counts were significantly lower in higher
plant populations in 1983 season. Possible reasons for population
patterns of bean flies are discussed.
Helpful links for
pest/crop interactions:
Consultative group on international agriculture research.
CGIAR's mission is to contribute to food security and poverty
eradication in developing countries through research, partnership,
capacity building, and policy support:
Helpful links for
intercropping in Africa:
Crop diversity aids in deterring pests. Intercropping can
also increase the resilience of the cropping system.
Mucuna spp., an aggressive Asian legume is a good
African cover crop.
This site explains why, and gives some history and useable information
pertaining to cover crops in general:
http://www.idrc.ca/books/focus/852/01-prefe.html
Up to date, species-specific descriptions of some
cover crops and "green"
manure. Limited applicability due to it covering many regions,
but a good
source:
http://ppathw3.cals.cornell.edu/mba_project/moist/mulchmail.html
Site offering new crop growing information to extension
workers in
Africa, somewhat vague, but easy to maneuver and easy to get information
from:
http://www.casin.org/sasakawa.htm#Crop
production demonstrations
Other useful links:
These links may offer additional assistance with African crops/pests/
or intercropping:
African agricultural research council. This offers
insight into recent research and has peripheral links:
http://www.arc.agric.za/fprojsrch.htm
This webpage was created on April 27th,
2000