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<strong>International</strong> <strong>Research</strong> Journal of Plant Science (ISSN: 2141-5447) Vol. 2(3) pp. 070-077, March, 2011<br />
Available online http://www.interesjournals.org/IRJPS<br />
Copyright © 2011 <strong>International</strong> <strong>Research</strong> <strong>Journals</strong><br />
<strong>Full</strong> length <strong>Research</strong> Paper<br />
Relationships between the occurrence of Desert locust<br />
(Schistocerca gregaria Forsk) and plant communities in<br />
Niger from 1965 to 2007<br />
Issoufou Dogo 1, L. Mina Idrissi Hassani2, Abdelghani Bouaichi3<br />
, Abdou Mamadou1, Garba Yahaya4, Issoufou Alfhari5.<br />
1 Direction Générale Protection des Végétaux, Niamey, Niger<br />
2 Faculté des Sciences Ibn Zohr, Agadir, Maroc,<br />
3 Centre National de Lutte Anti Acridienne, Agadir, Maroc,<br />
4 Centre National de Lutte Anti Acridienne, Niamey, Niger,<br />
5 Centre Régional Agrhymet, Niamey, Niger.<br />
Accepted 24 march, 2011<br />
The study of relationships between Desert locust and plant species evolving in the same habitat was<br />
realized on the basis of archives database of locust prospection conducted from 1965 to 2007 and<br />
available at the Crop Protection Directorate of Niger and the Regional <strong>International</strong> Organization for the<br />
Control of Migrant Pests based in Niger and Senegal. The objective set for this study is to know better<br />
the main plants having a certain affinity with Desert Locust to lead an efficient locust monitoring. The<br />
results obtained have shown that nearly 66% of the territory of Niger was affected by the presence of<br />
locust with a strong concentration in Aïr, Tamesna and Termit. For all the solitarious, gregarious and<br />
transiens of the Desert locust, the strongest correlations based on a level of significance higher than 0,<br />
5 are obtained with Tribulus terrestris, Acacia sp, Aerva javanica, Schouwia sp, Boerhavia coccinea,<br />
Citrullus sp and Panicum tirgidum. Two affinity groups of variables were identified. One containing<br />
gregarious adults and dominant woody plants and the other affected by the herbaceous plants<br />
contained hoppers, solitary and transiens adults.<br />
Key words: plant, correlation, Desert locust, occurrence, Niger<br />
INTRODUCTION<br />
Among the devastating pests of crops, Desert locust<br />
(Schistocera gregaria, Forsk, 1775, Orthoptera,<br />
Acrididae) occupies a prominent place and plays an<br />
important role during invasion period or major<br />
resurgence (Popov, 1958; Uvarov, 1977). Its economic<br />
impact extends to the majority of arid and semi-arid<br />
countries, from the west coast of Africa to India<br />
(Hemming et al., 1979; Lecoq, 2005).<br />
Its threat lies in its phases of transformation (Uvarov,<br />
1977), its high reproductive capacity, its migratory<br />
faculties, its large spectrum of polyphagy (Husain et al.,<br />
1946; FAO, 1967; Roffey and Popov, 1968) and its<br />
abilities to adapt itself to extreme ecological situations.<br />
*Corresponding author Email: issoufoudogo1@yahoo.fr<br />
Consequently, the Desert locust remains a major threat<br />
for the social and food stability, particularly for many<br />
rural people living on agriculture at high climatic risk<br />
(Lecoq, 2004).<br />
Niger which is a locust frontline, stretches on 1267000<br />
km 2 between the longitudes 00 ° 16’ and 16 ° 00 East, and<br />
the latitude 11°10’ and 23 ° 17’ North (CNEDD, 2006), and<br />
shelters important zones of summer reproduction and<br />
gregarization for Desert locust what are Tamesna and<br />
Aïr (Germaux et al., 1964; Pedgley, 1981). Among which<br />
is to add the area Termit potentially favorable<br />
(Mallamaire and Roy, 1958.) and in the past have<br />
attracted special attention from the monitoring teams of<br />
the Regional <strong>International</strong> Organization for the Control of<br />
Migrant Pests (OCLALAV).<br />
During the last generalized invasion of 1987-1989, the
ecorded losses of Niger were estimated at<br />
approximately 50% of the one million ha of grazing land<br />
and about 33% of around 12 000 ha of attacked rain-fed<br />
crops (Lecoq, 2003).The consequences of the invasion<br />
of 2004, combined to those of the drought have caused<br />
significant losses of cereal production (FAO/WFP, 2004).<br />
To delineate the extent damage caused by the high<br />
predation of locusts in areas of crops and pasturage is<br />
generally used chemical control (Steedman, 1988; FAO,<br />
1991) notwithstanding the adverse environmental and<br />
human health (Levitan et al., 1996; Langewald et al.,<br />
1999) and inadequacy of economic profitability (FAO,<br />
2003).<br />
Hence the interest of favoring approach prevention<br />
(Lomer et al., 2001) based on a permanent monitoring of<br />
locust in remission period and the control of gregarious<br />
populations (Roffey and Popov, 1968). It is the only<br />
strategy of struggle economically bearable and<br />
ecologically acceptable (Lecoq, 2004) because the<br />
recurrent costs can be lesser to those created by the<br />
simple management of necessary emergency<br />
assistances in period of invasion.<br />
Under current conditions in Niger, where access to<br />
certain parts of zones is often difficult due to its vast<br />
extent, problems of insecurity and the limited human and<br />
material means(Showler, 2003; FAO, 2010), a better<br />
knowledge of the habitats mostly attended by the Desert<br />
locust could contribute to a more efficient locust<br />
monitoring. Indeed, these habitats often colonized at<br />
various degrees by many plant species, which could be<br />
precious sources of food of, shelter for Locust, and play<br />
a big role in its spatiotemporal distribution.<br />
Through this present work, we will try to determine<br />
exclusively the correlation that could exist between<br />
Desert locust and plant species having evolved together<br />
in the same natural environment, while basing ourselves<br />
on the data archive collected during the prospection<br />
locust prospection led from 1965 to 2007 in Niger. The<br />
perception of this relationship could contribute to know of<br />
advantage the plants having a certain affinity with the<br />
Desert locust and to allow the reinforcement of predictive<br />
capacity teams of prospection in the planning of their<br />
monitoring activities focusing locust best sites colonized<br />
by these plants.<br />
Studies of this kind strictly centered on the archival<br />
data are rather rare or absent in the typical case of<br />
Niger. However, certain works already highlighted the<br />
importance of some plant species towards Desert locust<br />
through methods other than those based on the analysis<br />
of archival data. In fact, in the particular case of<br />
Mamadou et al. (2009) who led studies on the influence<br />
of fifteen plant species on the genesic activity in the<br />
Locust while carrying out a breeding out of cages in the<br />
valley of Tafidet in Niger. The work of Freiburg (2002)<br />
undertaken in Mauritania showed the part which can be<br />
played by the vegetation in the displacement of the larval<br />
bands in natural environment, by evaluating the damage<br />
Issoufou et al. 071<br />
caused using the method of analysis of density with an<br />
estimate of the damage. To determine qualitatively the<br />
food mode of the Locust, Benrima et al. (2002)<br />
compared the range of 50 plant species in the biotopes<br />
occupied by Schistocerca gregaria with those, which<br />
compose their feces.<br />
MATERIALS AND METHODS<br />
The documentary archives that have been exploited for the data<br />
collection stemmed from different locust prospection done all over<br />
Niger from 1965 to 2007 were come from OCLALAV and the Crop<br />
Protection Directorate (CPD) of Niger. The choice of this period is<br />
justified by the availability and regularity of data according to a<br />
step of monthly time in these structures.<br />
OCLALAV data<br />
OCLALAV data have covered the period going from 1965 to 1989.<br />
Since it stopped its activities in 1989, the documents have been<br />
stocked in its former offices in Dakar in Senegal and Zinder in<br />
Niger. For this last one, the archives have been kept in very bad<br />
conditions often piled on the floor in different offices that required a<br />
major dust before entering. The operation consisted in to<br />
extracting the whole documents related to Desert locust and its<br />
ecology then to sort and categorize them according to their nature<br />
(report of activities, bulletins, work, registers, notebook, and<br />
binders). The second step consisted in classifying them year per<br />
year in order to constitute series of reports bulletins of activities<br />
following a temporal, monthly and decade slot.<br />
CPD data<br />
The data collected have covered the period from 1990 to 2007 and<br />
have widely been provided by those collected at the National Anti-<br />
Locust Center of Agadez where the majority of document and<br />
information related to it one for the essential digitalized. Data from<br />
1996 to 2007 have already been recorded in a RAMSES-Niger<br />
base (Reconnaissance and Management System of the<br />
Environment Schistocerca) finalized by FAO.<br />
Data Processing<br />
Excel software under Windows have been used for the constitution<br />
of matrix data. The database created for the seizure of the<br />
recordings consists of two corpus named A and B. We put on line,<br />
sites (A), in column (B), all information about Locust and its<br />
environment that we ship called variables. These are as follows :<br />
date of list, the decade, name of the locality, geographic<br />
coordinates converted in decimal degree, year, month, solitary<br />
hoppers, transiens hoppers, gregarious hoppers, solitary adults,<br />
transiens adults, gregarious adults, bands, swarms, habitat, soils,<br />
prospected area, infected and treated as well as the different plant<br />
species. The set of all such information collected at a site surveyed<br />
was called registration.<br />
At the junction of each line and each column, qualitative variables<br />
(presence and absence) were used to make the presence or<br />
absence of Desert locust or plant species for each of the sites<br />
surveyed. To facilitate the treatment of this information, we have<br />
encoded these variables numerically by using value “1” for the<br />
presence and “0” for the absence.<br />
For the exclusive need of this study, it was extracted from initial<br />
database the records of locust’ presence (6), seven (7) grassy
072 Int. Res. J. Plant Sci.<br />
species and (6) woody species. The choice of these plant species<br />
from 70 genera identified are explained by their importance in<br />
number of frequency in our initial matrix and belongs to the<br />
principal plants reported by the studies of Germaux et al. (1964),<br />
Popov (1965) and Duranton et al. (1982).<br />
Designation of variables<br />
The nineteen (19) variables used for the study of this relationship<br />
titled as follows:<br />
Six (6) locust conditions: solitary hoppers, transiens hoppers,<br />
gregarious hoppers, solitary adults, transiens adults and<br />
gregarious adults;<br />
Six (6) species of the woody vegetation: Acacia sp, Balanites<br />
aegyptiaca, Indigofora sp, Maerua sp, Calotropis sp and<br />
Salvadoria persica;<br />
Seven (7) species of grassy vegetation like Aerva javanica,<br />
Aristidae sp, Boerhavia coccinea, Citrullus sp, Panicum tirgidum,<br />
Schouwia sp and Tribulus terrestris.<br />
Generation of maps<br />
From the initial matrix, we trained for each variable an Excel file<br />
formed by three columns: variable, latitude and longitude<br />
converted to decimal degree. The files thus formed, converted into<br />
<strong>Text</strong> file to be consistent with the device's System of Information<br />
for Geography (SIG) of the Regional Center of Agrhymet /Niamey/<br />
Niger. A layer of mesh at ¼ degree square geographic<br />
(approximately 50 km x 50 km) is used. This, for to be in adequacy<br />
with the work of Ould Baba (2001), Keita (2009) and of El Mouden<br />
(2009), which led studies on the cartographic distribution of locust<br />
presence thanks to the data archive of locust prospection .After the<br />
coupling of the <strong>Text</strong> file in tools SIG, we started the automatic<br />
process of generation of the maps.<br />
From the data of the table attribute maps of the 19 variables, we<br />
constituted a rectangular table in the form of matrix (X) articulated<br />
below and comprising N(1 to 295) lines and p(1 to 19) columns and with<br />
Xij like the frequency of presence of individual i (mesh i) for the<br />
variable J.<br />
Variables’ processing<br />
A Principal component analysis (PCA) was used for the data<br />
processing of the rectangular matrix (X) of the variables thanks to<br />
XLSTAT program, method which relays on a geometrical model<br />
according to Michael and Christopher (1999) and centered on the<br />
synthesis of information that a table of figures containing<br />
individuals and quantitative variables. It makes it possible to<br />
identify a possible similarity between the individuals and to<br />
determine the connection between the variables. This present<br />
analysis, which is exclusively about the variables, has aim to<br />
determine the links being able to exist between the locusts’<br />
variables on the one hand and plant variables on the other.<br />
The studies of cases of principal component analysis presented<br />
in the work of Pardoux et al. (2010) and Turler (2006) have been<br />
our reference for constructing the graph and interpreting the<br />
results. In this sense, our analysis conducted on two axes:<br />
a) The determination of the matrix of correlation to inform us<br />
about the intensity of the link and the direction of the correlation<br />
which can exist between the variables taken two by two on a level<br />
of 5 % significance.<br />
b) The determination of the number of the factorial axes to<br />
interpret by using the rule of Kaiser (1960) in order to proceed to<br />
the chart of the variables being able to allow us to identify the<br />
possible regrouping of the adjacent variables.<br />
RESULTS<br />
Distribution of the mesh<br />
In referring to the map generated for all variables, it<br />
appears for Niger, 448 meshes quarter-degree square<br />
mesh on which 295 showed the presence of locusts and<br />
/ or plants is 66% (Figure 1).<br />
Links between variables<br />
According to the signs and strengths of correlation<br />
between pairs of variables (Table 1), we distinguished<br />
two main groups.<br />
Strong supposed positive linear connections<br />
(correlations > 0, 50) in particular between:<br />
a) Solitary and Tribulus terrestris (r = 0,888),<br />
Schouwia sp (r = 0,862), Citrullus sp (r = 0,832), Aerva<br />
javanica (r = 0,818), Panicum tirgidum (r = 0,738),<br />
Acacia sp (r = 0,506);<br />
b) Transiens and Panicum tirgidum (r = 0,748),<br />
Acacia sp (r = 0,723), Schouwia sp (r = 0,655), Tribulus<br />
terrestris (r = 0,635), Citrullus sp (r = 0,649), Aristidae sp<br />
(r = 0,620), Boerhavia coccinea (r = 0,607), Balanites<br />
aegyptiaca (r = 0,541);<br />
c) Gregarious and Balanites aegyptiaca (r = 0,710),<br />
Acacia sp (r = 0,686), Aristidae sp (r = 0,581), Tribulus<br />
terrestris (r = 0,571), Panicum tirgidum (r = 0,654),<br />
Citrullus sp (r = 0,543) Boerhavia coccinea (r = 0,540),<br />
Schouwia sp (r = 0,529), Indigofora sp (r = 0,527).<br />
Low supposed positive linear connections (correlations <<br />
0, 50) mainly between:<br />
d) Solitary and Aristidae sp (r = 0,449), Calotropis<br />
procera (r = 0,387), Maerua sp (r = 0,335), Salvadoria<br />
persica (r = 0,210), Balanites aegyptiaca (r = 0,106),<br />
Indigofora sp (r = 0,078);<br />
e) Transiens and Maerua sp (r = 0,497), Aerva<br />
javanica (r = 0,484), Indigofora sp (r = 0,369), Salvadoria<br />
persica (r = 0,345), Calotropis procera (r = 0,330);<br />
f) Gregarious and Acacia sp (r = 0,425), Aristidae<br />
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.<br />
Table 1. Correlation Matrix [Pearson (n)]<br />
Variables<br />
Solitary<br />
adults<br />
Transiens<br />
adults<br />
Gregarious<br />
adults<br />
Solitary<br />
hoppers<br />
Transiens<br />
hoppers<br />
Issoufou et al. 073<br />
Gregarious<br />
hoppers<br />
Acacia sp 0,506 0,723 0,686 0,425 0,563 0,422<br />
Aerva javanica 0,818 0,484 0,350 0,720 0,383 0,263<br />
Aristidae sp 0,449 0,620 0,581 0,358 0,406 0,245<br />
Balanites aegyptiaca 0,106 0,541 0,710 0,079 0,301 0,380<br />
Boerhavia coccinea 0,708 0,607 0,540 0,624 0,433 0,219<br />
Citrullus sp 0,832 0,649 0,543 0,754 0,519 0,345<br />
Indigofora sp 0,078 0,369 0,527 0,071 0,115 0,067<br />
Maerua sp 0,335 0,497 0,380 0,235 0,339 0,148<br />
Panicum tirgidum 0,738 0,748 0,654 0,660 0,577 0,360<br />
Salvadoria persica 0,210 0,345 0,341 0,127 0,198 0,181<br />
Schouwia sp 0,862 0,655 0,529 0,829 0,576 0,407<br />
Tribulus terrestris 0,888 0,635 0,571 0,855 0,479 0,266<br />
Calotropis procera 0,387 0,330 0,284 0,305 0,258 0,116<br />
(r = 0, 2359, Salvadoria persica (r = 0,127), Balanites<br />
aegyptiaca (r = 0,079), Indigofora sp (r = 0,071).<br />
Choice of the factorial axes<br />
The application of the rule of Kaiser (1960), which<br />
recommends taking into account factors to proper values<br />
superior to 1, seems to be verified with the first three<br />
components of table 2. Thus, as the two first explain<br />
alone more than 70% of the total variance, they were<br />
retained for the graphic representation of variables<br />
consigned in figure 2.<br />
Analyses<br />
Based on the data matrix, we can group together<br />
meshes with the largest recorded Locust and plant<br />
frequencies in two different sectors.
074 Int. Res. J. Plant Sci.<br />
Table 2 . Eigen Values<br />
Component Main Eigenvalue Cumulative variance explained (%)<br />
1 10.609 55.838<br />
2 3.012 71.69<br />
3 1.766 80.987<br />
4 0.889 85.664<br />
5 0.685 89.267<br />
6 0.475 91.766<br />
7 0.36 93.66<br />
8 0.281 95.138<br />
9 0.226 96.325<br />
10 0.173 97.237<br />
11 0.119 97.863<br />
12 0.107 98.428<br />
13 0.085 98.876<br />
14 0.071 99.252<br />
15 0.05 99.517<br />
16 0.031 99.68<br />
17 0.025 99.811<br />
18 0.019 99.911<br />
19 0.017 100<br />
Figure 2. Graphic representation of variables<br />
The first which extends to the great ecological units from<br />
the Tamesna and Aïr, already defined by the work of<br />
Duranton et al.(1982) could cover the meshes M281 to<br />
M286, M254 to M259, M278 to M279, M336 to M241,<br />
M363 to M366, M390 to M395, M416 to M422, M416 to<br />
M422, M447 to M450, M472 to M475, M499 to M450,
M499 to M502 and M529, which extend between 16°00'<br />
and 19°00' north and 04°30' and 10° 00' east. These<br />
zones of strong frequency could be related to the large<br />
valleys fed by rainwater from the mountains of Aïr where<br />
the vegetation could be more important (Popov, 1965;<br />
Pedgley, 1981). They could be also assimilated to<br />
gregarious areas, confirming the status of the permanent<br />
habitat of Aïr and Tamesna reported by many authors<br />
(Popov, 1958; Germaux et al., 1964; Roeffy an Popov,<br />
1968; Uvarov, 1977; Pedgley, 1981).<br />
These areas are typically characterized by sandy and<br />
clayey soil, an annual pluviometric index lower than 200<br />
mm and vegetation composed of many herbaceous and<br />
woody species (Popov, 1965; Germal et al, 1964). Of<br />
these plants, we can note Schouwia sp, Tribulus<br />
terrestris, Panicum tirgidum, Citrullus sp, Aerva javanica,<br />
Boerhavia coccinea, Acacia sp and Balanites aegyptiaca<br />
, which are the subject of the present study.<br />
The second area could be made of meshes M603 to<br />
M606 and M630 to M631, which extend between 15°30'<br />
and 16°30' north, and 11° and 11°30 east, and are<br />
located in Termit. According to Saadou and al. (1998)<br />
and Popov (1965), this zone crossed by isohyets 100<br />
mm contains plants as Tribulus terrestris, Boerhavia sp,<br />
Aristida sp, Acacia sp and Maerua sp, which our study<br />
highlighted.<br />
Through this study, it arises from the matrix of<br />
correlation that the plant species having strong positive<br />
linear constraints with the three phases (solitary adults,<br />
gregarious adults and transiens adults) are Acacia sp,<br />
Aerva javanica, Boerhavia coccinea, Citrullus sp,<br />
Panicum tirgidum, Schouwia sp and Tribulus terrestris<br />
contrary to Maerua sp, Salvadoria persica and<br />
Calotropis procera, which present weak positive links.<br />
By referring to the studies of Turler (2006) and<br />
Pardoux et al. (2010) which report, that if two variable<br />
points are close to the circle and that their arrows form a<br />
weak angle, their correlation is strong, whereas it is<br />
almost null if the angle is of 90°. It thus emerges, of<br />
figure 2, that all the couples of the plant variables and<br />
locust are far away from the center and that the angles<br />
that they form between them are lower than 90°. We<br />
may thus, suppose that these variables are relatively<br />
correlated, thus corroborating the data of the matrix<br />
correlation. Apart from the confirmation of the force links,<br />
the graphic representation filters variables by showing<br />
two groups of affinities.<br />
The first on, composed of Tribulus terrestris, Schouwia<br />
sp, Citrullus sp, Aerva javanica, solitary hoppers, solitary<br />
adults, transiens adults and gregarious hoppers, is<br />
singularly dominated by grassy plants. This association<br />
could be justified by the accessibility that these types of<br />
plants, generally low, could offer to the hoppers and<br />
protection that they bring against predators and<br />
extremes temperatures. The possibility to meet hoppers<br />
in the areas of locust distribution in Niger, even in dry<br />
season, could find its justification in this association<br />
Issoufou et al. 075<br />
with these species. Which have the capacity to vegetate<br />
until cold season (January-February), when the rains<br />
recorded during the season is sufficient in certain Oueds<br />
of Aïr and Tamesna and in the edges of large valleys of<br />
Termit.<br />
The second group composed of gregarious adults,<br />
Acacia sp, Aristidae sp, Balanites aegyptiaca, Calotropis<br />
procera, Indigofora sp, Maerua sp, Panicum tirgidum,<br />
Salvadoria persica and Boerhavia coccinea, where<br />
woody plants mainly dominated. The preference of<br />
adults for plant tree could be explained by the fact that<br />
the mandibles of locusts are morphologically better<br />
adapted for gnawing the leaves of woody than<br />
herbaceous vegetation, and the gregarious usually fly<br />
day and night, they arise on wood (Latchininsky et al,<br />
1997).<br />
These two tendencies affinity that our study has<br />
highlighted, corroborate the works of Ashall and Chaney<br />
(1979) and Popov (1965) out of the two food behaviors<br />
recognized with the Locust where they reported that the<br />
adults feed on plants on which they pose in the late<br />
afternoon and early morning and the hoppers feed<br />
intermittently throughout the day by walking.<br />
The common elements that these plants could lay out<br />
and who are of a great interest for the herbivores in<br />
general and the Locust in particular would be their water<br />
content, in carbohydrate, in proteins and nitrogen, like<br />
those studies reported by Mamadou (2009), Correra<br />
(2006) and Simpson (2002).<br />
These links recorded between the plant variables and<br />
Locusts which could be expressed in the forms of food,<br />
shelters or perch and from which our study comes to put<br />
forward on the data basis of locust files, corroborate the<br />
results of certain work concerning the Desert locust and<br />
his food, although they were conducted by methods<br />
different from ours.<br />
Thus according to the results of the studies<br />
undertaken by Benrima et al.(2002), the plant species<br />
mostly appreciated by the Locust belong to the families<br />
of Boraginaceae, Poacaea, Zygophyllaceae, Solanaceae<br />
and Nyctaginaceae and those which are completely<br />
forsaken belong to the families like Capparidaceae,<br />
Convolvulaceae, Mimosaceae Cucurbitaceae and<br />
Asclepiadaceae. This is in adequacy with the whole of<br />
the species that we recorded apart from Citrullus sp,<br />
which presents a strong relation with the Locust although<br />
it belongs to the family of the Cucurbitaceous.<br />
In Niger, Mamadou et al. (2009) had to study the<br />
influence of fifteen plant species on the fecundity of the<br />
Locust in his two phase’s conditions in semi-controlled<br />
habitat. From these species, Schouwia thebaica,<br />
Boerhavia coccinea, Acacia sp, Panicum turgidum and<br />
Aristida sp belong to those, which are accepting mostly<br />
by the Locust. On the other hand, Cassia sp, Aerva<br />
javanica, Citrillus colocynthis, Salvadora persica and<br />
Calotropis procera belonged to the group of the least<br />
favorable species on the genesic plant , therefore the
076 Int. Res. J. Plant Sci.<br />
least consumed by the Locust; although our<br />
observations were noted a strong correlation with Aerva<br />
javanica and Citrillus sp.<br />
For the studies of Uvarov (1977), Schouwia thebaica,<br />
Tribulus terrestris and Boerhavia repens formed also<br />
part of the principal plant species, which composed the<br />
mode of food of the hopper’s locust. According to<br />
Philippe (1991), the association of Tribulus terrestis and<br />
Boehravia repens contributes to make of a station, a<br />
preferential habitat of the Locust which although<br />
polyphageous, expresses its preference for certain plant<br />
species such as Tribulus terrestris, Schouwia purperea,<br />
Aerva javanica (Popov, 1965; Chapman and Sword,<br />
1997). Our results confirm apparently this link between<br />
the Desert locust and these plants brought back by<br />
these authors.<br />
For the various plant species consumed by the<br />
hoppers of Locust, one can note Aerva javanica,<br />
Schouwia purpurea, Maerua crassifolia, Balanites<br />
aegypitiaca, Panicum turgidum, Boerhavia repens,<br />
Tribulus sp and Indigifora sp. Unlike Citrullus<br />
colocynthis, Calotropis procera and Aristida<br />
adscensionis rejected by the hoppers (Freiburg, 2002),<br />
although in the case of our study, the presence of<br />
Citrullus colocynthis was well correlated with Locust.<br />
Based on this observation, we can suppose that the part<br />
played by the latter could be that of a shelter.<br />
In the light of the results of our study and the works of<br />
some authors, it comes out that the plant species having<br />
privileged links with Desert Locust are none other than<br />
Acacia sp, Boerhavia sp, Panicum tirgidum, Schouwia<br />
sp Tribulus terrestris and Aerva javanica. Nevertheless<br />
the case of Citrullus sp whose link is variously<br />
appreciated deserves a special attention.<br />
These non-exhaustive results that we have just<br />
recorded subsequently consolidate the thesis according<br />
to which the Locust in his solitary phase despite its<br />
polyphagy, shows preferences which very often<br />
determine its presence on such or such other plant<br />
(Woldewahid et al., 2004; Popov, 1958), which could be<br />
used to better fight it.<br />
CONCLUSION<br />
The results of this study based on archives data of locust<br />
surveys that carried out from 1965 to 2007 in Niger, has<br />
enabled us to reinforce the major knowledge on the<br />
relationship plants-locust thanks to a Principal<br />
component analysis, notwithstanding its constraints<br />
often related to the choices of the axes and their<br />
interpretation.<br />
The importance of this relationship raised between the<br />
Locust and certain plant species mainly Boerhavia<br />
coccinea, Citrullus sp, Acacia sp, Tribulus terrestris,<br />
Schouwia and Aerva javanica, could be more<br />
consolidated by showing if this relationship depends on<br />
the preference of the food plants, their availability or<br />
other dissimulated factors. For this, studies could be<br />
conducted in areas with higher frequencies of locust and<br />
plant presence based on a phytosociological protocol<br />
adapted to enhance the results obtained from the<br />
archives.<br />
ACKNOWLEDGEMENTS<br />
At the end of this study, the authors thank the<br />
Department of Vegetation Protection of Niger and the<br />
responsible of former OCLALAV offices in Dakar,<br />
Senegal for making available to them all the archives.<br />
Their thanking go also goes to the PLUCP (Emergency<br />
Project to Fight against Desert Locust) in Niger and to<br />
Agryhmet Regional Center of Niamey respectively for<br />
their financial and material support. The Faculty of<br />
Sciences of Zohr University, Agadir, and Agadir’s Antilocust<br />
National Center in Morocco are duly thanked for<br />
technical support.<br />
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