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International Research Journal of Plant Science (ISSN: 2141-5447) Vol. 2(3) pp. 070-077, March, 2011
Available online http://www.interesjournals.org/IRJPS
Copyright © 2011 International Research Journals
Full length Research Paper
Relationships between the occurrence of Desert locust
(Schistocerca gregaria Forsk) and plant communities in
Niger from 1965 to 2007
Issoufou Dogo 1, L. Mina Idrissi Hassani2, Abdelghani Bouaichi3
, Abdou Mamadou1, Garba Yahaya4, Issoufou Alfhari5.
1 Direction Générale Protection des Végétaux, Niamey, Niger
2 Faculté des Sciences Ibn Zohr, Agadir, Maroc,
3 Centre National de Lutte Anti Acridienne, Agadir, Maroc,
4 Centre National de Lutte Anti Acridienne, Niamey, Niger,
5 Centre Régional Agrhymet, Niamey, Niger.
Accepted 24 march, 2011
The study of relationships between Desert locust and plant species evolving in the same habitat was
realized on the basis of archives database of locust prospection conducted from 1965 to 2007 and
available at the Crop Protection Directorate of Niger and the Regional International Organization for the
Control of Migrant Pests based in Niger and Senegal. The objective set for this study is to know better
the main plants having a certain affinity with Desert Locust to lead an efficient locust monitoring. The
results obtained have shown that nearly 66% of the territory of Niger was affected by the presence of
locust with a strong concentration in Aïr, Tamesna and Termit. For all the solitarious, gregarious and
transiens of the Desert locust, the strongest correlations based on a level of significance higher than 0,
5 are obtained with Tribulus terrestris, Acacia sp, Aerva javanica, Schouwia sp, Boerhavia coccinea,
Citrullus sp and Panicum tirgidum. Two affinity groups of variables were identified. One containing
gregarious adults and dominant woody plants and the other affected by the herbaceous plants
contained hoppers, solitary and transiens adults.
Key words: plant, correlation, Desert locust, occurrence, Niger
INTRODUCTION
Among the devastating pests of crops, Desert locust
(Schistocera gregaria, Forsk, 1775, Orthoptera,
Acrididae) occupies a prominent place and plays an
important role during invasion period or major
resurgence (Popov, 1958; Uvarov, 1977). Its economic
impact extends to the majority of arid and semi-arid
countries, from the west coast of Africa to India
(Hemming et al., 1979; Lecoq, 2005).
Its threat lies in its phases of transformation (Uvarov,
1977), its high reproductive capacity, its migratory
faculties, its large spectrum of polyphagy (Husain et al.,
1946; FAO, 1967; Roffey and Popov, 1968) and its
abilities to adapt itself to extreme ecological situations.
*Corresponding author Email: issoufoudogo1@yahoo.fr
Consequently, the Desert locust remains a major threat
for the social and food stability, particularly for many
rural people living on agriculture at high climatic risk
(Lecoq, 2004).
Niger which is a locust frontline, stretches on 1267000
km 2 between the longitudes 00 ° 16’ and 16 ° 00 East, and
the latitude 11°10’ and 23 ° 17’ North (CNEDD, 2006), and
shelters important zones of summer reproduction and
gregarization for Desert locust what are Tamesna and
Aïr (Germaux et al., 1964; Pedgley, 1981). Among which
is to add the area Termit potentially favorable
(Mallamaire and Roy, 1958.) and in the past have
attracted special attention from the monitoring teams of
the Regional International Organization for the Control of
Migrant Pests (OCLALAV).
During the last generalized invasion of 1987-1989, the

ecorded losses of Niger were estimated at
approximately 50% of the one million ha of grazing land
and about 33% of around 12 000 ha of attacked rain-fed
crops (Lecoq, 2003).The consequences of the invasion
of 2004, combined to those of the drought have caused
significant losses of cereal production (FAO/WFP, 2004).
To delineate the extent damage caused by the high
predation of locusts in areas of crops and pasturage is
generally used chemical control (Steedman, 1988; FAO,
1991) notwithstanding the adverse environmental and
human health (Levitan et al., 1996; Langewald et al.,
1999) and inadequacy of economic profitability (FAO,
2003).
Hence the interest of favoring approach prevention
(Lomer et al., 2001) based on a permanent monitoring of
locust in remission period and the control of gregarious
populations (Roffey and Popov, 1968). It is the only
strategy of struggle economically bearable and
ecologically acceptable (Lecoq, 2004) because the
recurrent costs can be lesser to those created by the
simple management of necessary emergency
assistances in period of invasion.
Under current conditions in Niger, where access to
certain parts of zones is often difficult due to its vast
extent, problems of insecurity and the limited human and
material means(Showler, 2003; FAO, 2010), a better
knowledge of the habitats mostly attended by the Desert
locust could contribute to a more efficient locust
monitoring. Indeed, these habitats often colonized at
various degrees by many plant species, which could be
precious sources of food of, shelter for Locust, and play
a big role in its spatiotemporal distribution.
Through this present work, we will try to determine
exclusively the correlation that could exist between
Desert locust and plant species having evolved together
in the same natural environment, while basing ourselves
on the data archive collected during the prospection
locust prospection led from 1965 to 2007 in Niger. The
perception of this relationship could contribute to know of
advantage the plants having a certain affinity with the
Desert locust and to allow the reinforcement of predictive
capacity teams of prospection in the planning of their
monitoring activities focusing locust best sites colonized
by these plants.
Studies of this kind strictly centered on the archival
data are rather rare or absent in the typical case of
Niger. However, certain works already highlighted the
importance of some plant species towards Desert locust
through methods other than those based on the analysis
of archival data. In fact, in the particular case of
Mamadou et al. (2009) who led studies on the influence
of fifteen plant species on the genesic activity in the
Locust while carrying out a breeding out of cages in the
valley of Tafidet in Niger. The work of Freiburg (2002)
undertaken in Mauritania showed the part which can be
played by the vegetation in the displacement of the larval
bands in natural environment, by evaluating the damage
Issoufou et al. 071
caused using the method of analysis of density with an
estimate of the damage. To determine qualitatively the
food mode of the Locust, Benrima et al. (2002)
compared the range of 50 plant species in the biotopes
occupied by Schistocerca gregaria with those, which
compose their feces.
MATERIALS AND METHODS
The documentary archives that have been exploited for the data
collection stemmed from different locust prospection done all over
Niger from 1965 to 2007 were come from OCLALAV and the Crop
Protection Directorate (CPD) of Niger. The choice of this period is
justified by the availability and regularity of data according to a
step of monthly time in these structures.
OCLALAV data
OCLALAV data have covered the period going from 1965 to 1989.
Since it stopped its activities in 1989, the documents have been
stocked in its former offices in Dakar in Senegal and Zinder in
Niger. For this last one, the archives have been kept in very bad
conditions often piled on the floor in different offices that required a
major dust before entering. The operation consisted in to
extracting the whole documents related to Desert locust and its
ecology then to sort and categorize them according to their nature
(report of activities, bulletins, work, registers, notebook, and
binders). The second step consisted in classifying them year per
year in order to constitute series of reports bulletins of activities
following a temporal, monthly and decade slot.
CPD data
The data collected have covered the period from 1990 to 2007 and
have widely been provided by those collected at the National Anti-
Locust Center of Agadez where the majority of document and
information related to it one for the essential digitalized. Data from
1996 to 2007 have already been recorded in a RAMSES-Niger
base (Reconnaissance and Management System of the
Environment Schistocerca) finalized by FAO.
Data Processing
Excel software under Windows have been used for the constitution
of matrix data. The database created for the seizure of the
recordings consists of two corpus named A and B. We put on line,
sites (A), in column (B), all information about Locust and its
environment that we ship called variables. These are as follows :
date of list, the decade, name of the locality, geographic
coordinates converted in decimal degree, year, month, solitary
hoppers, transiens hoppers, gregarious hoppers, solitary adults,
transiens adults, gregarious adults, bands, swarms, habitat, soils,
prospected area, infected and treated as well as the different plant
species. The set of all such information collected at a site surveyed
was called registration.
At the junction of each line and each column, qualitative variables
(presence and absence) were used to make the presence or
absence of Desert locust or plant species for each of the sites
surveyed. To facilitate the treatment of this information, we have
encoded these variables numerically by using value “1” for the
presence and “0” for the absence.
For the exclusive need of this study, it was extracted from initial
database the records of locust’ presence (6), seven (7) grassy

072 Int. Res. J. Plant Sci.
species and (6) woody species. The choice of these plant species
from 70 genera identified are explained by their importance in
number of frequency in our initial matrix and belongs to the
principal plants reported by the studies of Germaux et al. (1964),
Popov (1965) and Duranton et al. (1982).
Designation of variables
The nineteen (19) variables used for the study of this relationship
titled as follows:
Six (6) locust conditions: solitary hoppers, transiens hoppers,
gregarious hoppers, solitary adults, transiens adults and
gregarious adults;
Six (6) species of the woody vegetation: Acacia sp, Balanites
aegyptiaca, Indigofora sp, Maerua sp, Calotropis sp and
Salvadoria persica;
Seven (7) species of grassy vegetation like Aerva javanica,
Aristidae sp, Boerhavia coccinea, Citrullus sp, Panicum tirgidum,
Schouwia sp and Tribulus terrestris.
Generation of maps
From the initial matrix, we trained for each variable an Excel file
formed by three columns: variable, latitude and longitude
converted to decimal degree. The files thus formed, converted into
Text file to be consistent with the device's System of Information
for Geography (SIG) of the Regional Center of Agrhymet /Niamey/
Niger. A layer of mesh at ¼ degree square geographic
(approximately 50 km x 50 km) is used. This, for to be in adequacy
with the work of Ould Baba (2001), Keita (2009) and of El Mouden
(2009), which led studies on the cartographic distribution of locust
presence thanks to the data archive of locust prospection .After the
coupling of the Text file in tools SIG, we started the automatic
process of generation of the maps.
From the data of the table attribute maps of the 19 variables, we
constituted a rectangular table in the form of matrix (X) articulated
below and comprising N(1 to 295) lines and p(1 to 19) columns and with
Xij like the frequency of presence of individual i (mesh i) for the
variable J.
Variables’ processing
A Principal component analysis (PCA) was used for the data
processing of the rectangular matrix (X) of the variables thanks to
XLSTAT program, method which relays on a geometrical model
according to Michael and Christopher (1999) and centered on the
synthesis of information that a table of figures containing
individuals and quantitative variables. It makes it possible to
identify a possible similarity between the individuals and to
determine the connection between the variables. This present
analysis, which is exclusively about the variables, has aim to
determine the links being able to exist between the locusts’
variables on the one hand and plant variables on the other.
The studies of cases of principal component analysis presented
in the work of Pardoux et al. (2010) and Turler (2006) have been
our reference for constructing the graph and interpreting the
results. In this sense, our analysis conducted on two axes:
a) The determination of the matrix of correlation to inform us
about the intensity of the link and the direction of the correlation
which can exist between the variables taken two by two on a level
of 5 % significance.
b) The determination of the number of the factorial axes to
interpret by using the rule of Kaiser (1960) in order to proceed to
the chart of the variables being able to allow us to identify the
possible regrouping of the adjacent variables.
RESULTS
Distribution of the mesh
In referring to the map generated for all variables, it
appears for Niger, 448 meshes quarter-degree square
mesh on which 295 showed the presence of locusts and
/ or plants is 66% (Figure 1).
Links between variables
According to the signs and strengths of correlation
between pairs of variables (Table 1), we distinguished
two main groups.
Strong supposed positive linear connections
(correlations > 0, 50) in particular between:
a) Solitary and Tribulus terrestris (r = 0,888),
Schouwia sp (r = 0,862), Citrullus sp (r = 0,832), Aerva
javanica (r = 0,818), Panicum tirgidum (r = 0,738),
Acacia sp (r = 0,506);
b) Transiens and Panicum tirgidum (r = 0,748),
Acacia sp (r = 0,723), Schouwia sp (r = 0,655), Tribulus
terrestris (r = 0,635), Citrullus sp (r = 0,649), Aristidae sp
(r = 0,620), Boerhavia coccinea (r = 0,607), Balanites
aegyptiaca (r = 0,541);
c) Gregarious and Balanites aegyptiaca (r = 0,710),
Acacia sp (r = 0,686), Aristidae sp (r = 0,581), Tribulus
terrestris (r = 0,571), Panicum tirgidum (r = 0,654),
Citrullus sp (r = 0,543) Boerhavia coccinea (r = 0,540),
Schouwia sp (r = 0,529), Indigofora sp (r = 0,527).
Low supposed positive linear connections (correlations <
0, 50) mainly between:
d) Solitary and Aristidae sp (r = 0,449), Calotropis
procera (r = 0,387), Maerua sp (r = 0,335), Salvadoria
persica (r = 0,210), Balanites aegyptiaca (r = 0,106),
Indigofora sp (r = 0,078);
e) Transiens and Maerua sp (r = 0,497), Aerva
javanica (r = 0,484), Indigofora sp (r = 0,369), Salvadoria
persica (r = 0,345), Calotropis procera (r = 0,330);
f) Gregarious and Acacia sp (r = 0,425), Aristidae
sp (r = 0,358), Calotropis procera (r = 0,305), Maerua sp

Figure1. Mesh layer frequencies of Desert locust and plants from 1965 to 2007 in Niger.
Table 1. Correlation Matrix [Pearson (n)]
Variables
Solitary
adults
Transiens
adults
Gregarious
adults
Solitary
hoppers
Transiens
hoppers
Issoufou et al. 073
Gregarious
hoppers
Acacia sp 0,506 0,723 0,686 0,425 0,563 0,422
Aerva javanica 0,818 0,484 0,350 0,720 0,383 0,263
Aristidae sp 0,449 0,620 0,581 0,358 0,406 0,245
Balanites aegyptiaca 0,106 0,541 0,710 0,079 0,301 0,380
Boerhavia coccinea 0,708 0,607 0,540 0,624 0,433 0,219
Citrullus sp 0,832 0,649 0,543 0,754 0,519 0,345
Indigofora sp 0,078 0,369 0,527 0,071 0,115 0,067
Maerua sp 0,335 0,497 0,380 0,235 0,339 0,148
Panicum tirgidum 0,738 0,748 0,654 0,660 0,577 0,360
Salvadoria persica 0,210 0,345 0,341 0,127 0,198 0,181
Schouwia sp 0,862 0,655 0,529 0,829 0,576 0,407
Tribulus terrestris 0,888 0,635 0,571 0,855 0,479 0,266
Calotropis procera 0,387 0,330 0,284 0,305 0,258 0,116
(r = 0, 2359, Salvadoria persica (r = 0,127), Balanites
aegyptiaca (r = 0,079), Indigofora sp (r = 0,071).
Choice of the factorial axes
The application of the rule of Kaiser (1960), which
recommends taking into account factors to proper values
superior to 1, seems to be verified with the first three
components of table 2. Thus, as the two first explain
alone more than 70% of the total variance, they were
retained for the graphic representation of variables
consigned in figure 2.
Analyses
Based on the data matrix, we can group together
meshes with the largest recorded Locust and plant
frequencies in two different sectors.

074 Int. Res. J. Plant Sci.
Table 2 . Eigen Values
Component Main Eigenvalue Cumulative variance explained (%)
1 10.609 55.838
2 3.012 71.69
3 1.766 80.987
4 0.889 85.664
5 0.685 89.267
6 0.475 91.766
7 0.36 93.66
8 0.281 95.138
9 0.226 96.325
10 0.173 97.237
11 0.119 97.863
12 0.107 98.428
13 0.085 98.876
14 0.071 99.252
15 0.05 99.517
16 0.031 99.68
17 0.025 99.811
18 0.019 99.911
19 0.017 100
Figure 2. Graphic representation of variables
The first which extends to the great ecological units from
the Tamesna and Aïr, already defined by the work of
Duranton et al.(1982) could cover the meshes M281 to
M286, M254 to M259, M278 to M279, M336 to M241,
M363 to M366, M390 to M395, M416 to M422, M416 to
M422, M447 to M450, M472 to M475, M499 to M450,

M499 to M502 and M529, which extend between 16°00'
and 19°00' north and 04°30' and 10° 00' east. These
zones of strong frequency could be related to the large
valleys fed by rainwater from the mountains of Aïr where
the vegetation could be more important (Popov, 1965;
Pedgley, 1981). They could be also assimilated to
gregarious areas, confirming the status of the permanent
habitat of Aïr and Tamesna reported by many authors
(Popov, 1958; Germaux et al., 1964; Roeffy an Popov,
1968; Uvarov, 1977; Pedgley, 1981).
These areas are typically characterized by sandy and
clayey soil, an annual pluviometric index lower than 200
mm and vegetation composed of many herbaceous and
woody species (Popov, 1965; Germal et al, 1964). Of
these plants, we can note Schouwia sp, Tribulus
terrestris, Panicum tirgidum, Citrullus sp, Aerva javanica,
Boerhavia coccinea, Acacia sp and Balanites aegyptiaca
, which are the subject of the present study.
The second area could be made of meshes M603 to
M606 and M630 to M631, which extend between 15°30'
and 16°30' north, and 11° and 11°30 east, and are
located in Termit. According to Saadou and al. (1998)
and Popov (1965), this zone crossed by isohyets 100
mm contains plants as Tribulus terrestris, Boerhavia sp,
Aristida sp, Acacia sp and Maerua sp, which our study
highlighted.
Through this study, it arises from the matrix of
correlation that the plant species having strong positive
linear constraints with the three phases (solitary adults,
gregarious adults and transiens adults) are Acacia sp,
Aerva javanica, Boerhavia coccinea, Citrullus sp,
Panicum tirgidum, Schouwia sp and Tribulus terrestris
contrary to Maerua sp, Salvadoria persica and
Calotropis procera, which present weak positive links.
By referring to the studies of Turler (2006) and
Pardoux et al. (2010) which report, that if two variable
points are close to the circle and that their arrows form a
weak angle, their correlation is strong, whereas it is
almost null if the angle is of 90°. It thus emerges, of
figure 2, that all the couples of the plant variables and
locust are far away from the center and that the angles
that they form between them are lower than 90°. We
may thus, suppose that these variables are relatively
correlated, thus corroborating the data of the matrix
correlation. Apart from the confirmation of the force links,
the graphic representation filters variables by showing
two groups of affinities.
The first on, composed of Tribulus terrestris, Schouwia
sp, Citrullus sp, Aerva javanica, solitary hoppers, solitary
adults, transiens adults and gregarious hoppers, is
singularly dominated by grassy plants. This association
could be justified by the accessibility that these types of
plants, generally low, could offer to the hoppers and
protection that they bring against predators and
extremes temperatures. The possibility to meet hoppers
in the areas of locust distribution in Niger, even in dry
season, could find its justification in this association
Issoufou et al. 075
with these species. Which have the capacity to vegetate
until cold season (January-February), when the rains
recorded during the season is sufficient in certain Oueds
of Aïr and Tamesna and in the edges of large valleys of
Termit.
The second group composed of gregarious adults,
Acacia sp, Aristidae sp, Balanites aegyptiaca, Calotropis
procera, Indigofora sp, Maerua sp, Panicum tirgidum,
Salvadoria persica and Boerhavia coccinea, where
woody plants mainly dominated. The preference of
adults for plant tree could be explained by the fact that
the mandibles of locusts are morphologically better
adapted for gnawing the leaves of woody than
herbaceous vegetation, and the gregarious usually fly
day and night, they arise on wood (Latchininsky et al,
1997).
These two tendencies affinity that our study has
highlighted, corroborate the works of Ashall and Chaney
(1979) and Popov (1965) out of the two food behaviors
recognized with the Locust where they reported that the
adults feed on plants on which they pose in the late
afternoon and early morning and the hoppers feed
intermittently throughout the day by walking.
The common elements that these plants could lay out
and who are of a great interest for the herbivores in
general and the Locust in particular would be their water
content, in carbohydrate, in proteins and nitrogen, like
those studies reported by Mamadou (2009), Correra
(2006) and Simpson (2002).
These links recorded between the plant variables and
Locusts which could be expressed in the forms of food,
shelters or perch and from which our study comes to put
forward on the data basis of locust files, corroborate the
results of certain work concerning the Desert locust and
his food, although they were conducted by methods
different from ours.
Thus according to the results of the studies
undertaken by Benrima et al.(2002), the plant species
mostly appreciated by the Locust belong to the families
of Boraginaceae, Poacaea, Zygophyllaceae, Solanaceae
and Nyctaginaceae and those which are completely
forsaken belong to the families like Capparidaceae,
Convolvulaceae, Mimosaceae Cucurbitaceae and
Asclepiadaceae. This is in adequacy with the whole of
the species that we recorded apart from Citrullus sp,
which presents a strong relation with the Locust although
it belongs to the family of the Cucurbitaceous.
In Niger, Mamadou et al. (2009) had to study the
influence of fifteen plant species on the fecundity of the
Locust in his two phase’s conditions in semi-controlled
habitat. From these species, Schouwia thebaica,
Boerhavia coccinea, Acacia sp, Panicum turgidum and
Aristida sp belong to those, which are accepting mostly
by the Locust. On the other hand, Cassia sp, Aerva
javanica, Citrillus colocynthis, Salvadora persica and
Calotropis procera belonged to the group of the least
favorable species on the genesic plant , therefore the

076 Int. Res. J. Plant Sci.
least consumed by the Locust; although our
observations were noted a strong correlation with Aerva
javanica and Citrillus sp.
For the studies of Uvarov (1977), Schouwia thebaica,
Tribulus terrestris and Boerhavia repens formed also
part of the principal plant species, which composed the
mode of food of the hopper’s locust. According to
Philippe (1991), the association of Tribulus terrestis and
Boehravia repens contributes to make of a station, a
preferential habitat of the Locust which although
polyphageous, expresses its preference for certain plant
species such as Tribulus terrestris, Schouwia purperea,
Aerva javanica (Popov, 1965; Chapman and Sword,
1997). Our results confirm apparently this link between
the Desert locust and these plants brought back by
these authors.
For the various plant species consumed by the
hoppers of Locust, one can note Aerva javanica,
Schouwia purpurea, Maerua crassifolia, Balanites
aegypitiaca, Panicum turgidum, Boerhavia repens,
Tribulus sp and Indigifora sp. Unlike Citrullus
colocynthis, Calotropis procera and Aristida
adscensionis rejected by the hoppers (Freiburg, 2002),
although in the case of our study, the presence of
Citrullus colocynthis was well correlated with Locust.
Based on this observation, we can suppose that the part
played by the latter could be that of a shelter.
In the light of the results of our study and the works of
some authors, it comes out that the plant species having
privileged links with Desert Locust are none other than
Acacia sp, Boerhavia sp, Panicum tirgidum, Schouwia
sp Tribulus terrestris and Aerva javanica. Nevertheless
the case of Citrullus sp whose link is variously
appreciated deserves a special attention.
These non-exhaustive results that we have just
recorded subsequently consolidate the thesis according
to which the Locust in his solitary phase despite its
polyphagy, shows preferences which very often
determine its presence on such or such other plant
(Woldewahid et al., 2004; Popov, 1958), which could be
used to better fight it.
CONCLUSION
The results of this study based on archives data of locust
surveys that carried out from 1965 to 2007 in Niger, has
enabled us to reinforce the major knowledge on the
relationship plants-locust thanks to a Principal
component analysis, notwithstanding its constraints
often related to the choices of the axes and their
interpretation.
The importance of this relationship raised between the
Locust and certain plant species mainly Boerhavia
coccinea, Citrullus sp, Acacia sp, Tribulus terrestris,
Schouwia and Aerva javanica, could be more
consolidated by showing if this relationship depends on
the preference of the food plants, their availability or
other dissimulated factors. For this, studies could be
conducted in areas with higher frequencies of locust and
plant presence based on a phytosociological protocol
adapted to enhance the results obtained from the
archives.
ACKNOWLEDGEMENTS
At the end of this study, the authors thank the
Department of Vegetation Protection of Niger and the
responsible of former OCLALAV offices in Dakar,
Senegal for making available to them all the archives.
Their thanking go also goes to the PLUCP (Emergency
Project to Fight against Desert Locust) in Niger and to
Agryhmet Regional Center of Niamey respectively for
their financial and material support. The Faculty of
Sciences of Zohr University, Agadir, and Agadir’s Antilocust
National Center in Morocco are duly thanked for
technical support.
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