Oedaleus Senegalensis Research Articles

Generational variation in nutrient regulation for an outbreaking herbivore

Multivoltine insects can produce multiple generations in one year. Favorable conditions support more generations, leading to serious outbreaks. For herbivores, plant nutrient availability is a major environmental factor affecting fitness and it can shift substantially throughout seasons. In a stochastic environment, organisms can adopt several strategies to regulate their nutrient intake and maximize performance. However, data regarding nutrient regulation of wild herbivores are scarce, and even more so regarding potential intergenerational plasticity. To bridge this gap, we measured nutritional regulation and performance of an outbreaking multivoltine herbivore – one of the most serious agricultural pests in the Sahel:Oedaleus senegalensis. We surveyed a field population in Senegal and measured its nutritional preference and regulation across two generations (G1 and G3) using artificial diets and plant choice experiments. In the field, G1 locusts were five to ten times more abundant than G3 locusts. We found that G1 and G3 locusts selected different protein:carbohydrate ratios but also that the strength of regulation was different. G1 locusts regulated their nutrient target more tightly than G3 locusts. In contrast, studies with laboratory populations demonstrate strong regulation for grasshoppers, appearing less plastic than field populations. Both generations selected a carbohydrate‐biased nutrient ratio, although it was more carbohydrate‐biased for G3 locusts. In both cases, plant nutrient contents in the field were more protein biased than their preferred diet. Therefore, choices by locusts were likely influenced by other ecological variables such as leaf toughness or plant defenses. G1females were heavier and laid more eggs than G3 females. However, G3 locusts survived longer during the experiment than G1 locusts, suggesting a potential generational tradeoff between reproduction and survival. Our data highlight the importance of studying nutritional regulation in situ and incorporating field and lab data to better understand foraging decisions and nutritional tradeoffs.

Checklist and taxonomic updates in grasshoppers (Orthoptera: Caelifera) of central and southwestern Tunisia with new records and a key for species identification

Since the publication of Chopard's 1943 book, Les Orthopteroides d'Afrique du Nord, the diversity of Orthoptera in Tunisia has not been studied or prospected except for 20 publications. Furthermore, the classification of Orthoptera has changed since 1943 due to taxonomic and phylogenetic advances. To allow a full survey of the Tunisian grasshopper fauna, it is thus necessary first to correctly survey the biological diversity of grasshoppers in Tunisia, and second to have an updated taxonomic reference in order to describe this diversity and compare it with the grasshopper faunas in the other countries of the Maghreb. In the present paper, we propose an updated checklist and a key for the identification of Tunisian grasshoppers, based primarily on field sampling in central and southwestern Tunisia, and literature data for other Tunisian areas. Each species is documented with habitus photographs, geographical distribution, and type of habitat. In total, for the prospected areas, 75 species of Caelifera belonging to five families and 43 genera are listed, while 83 species were recorded up to now for the whole Tunisia. Among these 75 species, seven are newly recorded for Tunisia, i.e., Sphodromerus decoloratusFinot, 1894, Egnatioides coerulans (Krauss, 1893), Dociostaurus biskrensisMoussi & Petit, 2014, Aiolopus puissanti Defaut, 2005, Hilethera aeolopoides (Uvarov, 1922), Leptopternis rothschildiBolivar, 1913, and Tenuitarsus angustus (Blanchard, 1836); and one species is newly recorded for central and southwestern Tunisia, i.e., Oedipoda fuscocincta fuscocinctaLucas, 1849. We also confirm the presence of two species that were only tentatively recorded in Tunisia, i.e., Oedaleus senegalensis (Krauss, 1877) and Stenohippus mundus (Walker, 1871). DNA sequences (COI, ND2 and H3) are presented for 26 taxa, as a first step towards barcoding all Tunisian caeliferan taxa.

Physiological status is a stronger predictor of nutrient selection than ambient plant nutrient content for a wild herbivore.

There is generally a close relationship between a consumer's food and its optimal nutrients. When there is a mismatch, it is hypothesized that mobile herbivores switch between food items to balance nutrients, however, there are limited data for field populations. In this study, we measured ambient plant nutrient content at two time points and contrasted our results with the nutrient ratio selected by wild female and male grasshoppers (Oedaleus senegalensis). Few plants were near O. senegalensis' optimal protein:carbohydrate ratio (P:C), nor were plants complementary. Grasshoppers collected earlier all regulated for a carbohydrate-biased ratio but females ate slightly more protein. We hypothesized that the long migration undertaken by this species may explain its carbohydrate needs. In contrast to most laboratory studies, grasshoppers collected later did not tightly regulate their P:C. These results suggest that field populations are not shifting their P:C to match seasonal plant nutrient shifts and that mobile herbivores rely on post-ingestive mechanisms in the face of environmental variation. Because this is among the first studies to examine the relationship between ambient nutrient landscape and physiological state our data are a key step in bridging knowledge acquired from lab studies to hypotheses regarding the role ecological factors play in foraging strategies.

Linking land use and the nutritional ecology of herbivores: A case study with the Senegalese locust

Abstract Access to high‐quality food is a main driver of population dynamics. For herbivores, protein and carbohydrates are key nutrients that are notoriously variable in plants and are affected by land use. However, few studies have linked foraging decisions and performance in the laboratory to the nutritional landscape available in the field. Oedaleus senegalensis is a non‐model locust, a grass‐feeder, and the main pest of millet, a subsistence crop in the Sahel. In this study, we examined dietary preference and locust performance across a range of protein:carbohydrate ratios using the Geometric Framework methodology. We then applied a fitness landscape approach to visualize these results with the plant nutrient contents available across four land‐use types: millet, groundnut, fallow, and grazed fields. Finally, we contrasted our results with locust distribution in the field. Several locust species (O. senegalensis included) exhibit density‐dependent colour polymorphism; thus, we also reported individual coloration (brown or green). We found that O. senegalensis preferred moderately carbohydrate‐biased food 1:1.6 protein:carbohydrate ratio. All traits recorded (mass gain, development time, growth rate, moult success and performance index) were best near that ratio and declined on either side presenting a ‘hump‐shape’. Fallow fields contained more plants, particularly grasses, that were both abundant and closer to the optimal protein:carbohydrate ratio recorded from the laboratory experiments. When we surveyed O. senegalensis abundance and proportion, we found that they were more numerous in the fallow fields. Brown morph individuals, the ones associated with high density, were proportionally more abundant in fallow fields than green individuals. Our study provides evidence that variation in nutritional landscapes – relative to an herbivore's optimal nutrient balance – is a key driver of herbivore population distribution and abundance, and can be used to predict bottom‐up effects on herbivore species.

Soil-targeted interventions could alleviate locust and grasshopper pest pressure in West Africa

Agricultural land use has intended and unintended consequences for human livelihoods through feedbacks within coupled human and natural systems. In Senegal, West Africa, soils are a vital resource for livelihoods and food security in smallholder farming communities. In this study, we explored the connections among land use, soil conditions, plant nutrient content, and the abundance of several locust and grasshopper species. We worked in two rural farming villages in the Kaffrine region of Senegal. Oedaleus senegalensis was least abundant in groundnut areas where plant N was highest and abundance was negatively correlated with plant N across land use types. Overall, grasshoppers were most numerous in grazing and fallow areas. There was little variation in soil properties across land use types and soil organic matter (SOM) and inorganic soil N content were low throughout. SOM was positively correlated with soil inorganic N concentration, which in turn was positively correlated with plant N content. Of the management practices we surveyed, fallowing fields was important for soil N and SOM replenishment. These results corroborate other research indicating that land use, management practices, soil and plant nutrients, and insect herbivore abundance are mechanistically coupled. Although further research is needed, improving soil fertility could be used as an alternative to pesticides to keep locusts at bay and improve crop yields.

Observation on the Epiphallus and spermatheca in Oedaleus senegalensis Krauss (Acrididae:Orthoptera)

The genus Oedaleus Fieber, is considered as economically important pest. During the present study fair numbers of female Oedaleus senegalensis Krauss were collected and dissected and following observation on spermatheca were noted down. Spermatheca coiled shaped ectodermal duct of origin. Pre–apical diverticulum slightly larger and finger like placed laterally it is rounded at apex while sac shaped Apical diverticulum with broaden, extended with curved process at stand. It is of varying sizes and shapes. Beside this, it was noted that this species is often associated with mesoxerophilic habitats and can be categorized as graminivorous. In addition of this, it has a certain importance because of the damage that it causes loss to consumer crops i-e (maize, bajra, rice, wheat etc), almost seedlings or nursery and un-ripe stages in fields. This species were considered as pest because it causes damage on valuable crops in various parts of Pakistan.

A simple tentative model of the losses caused by the Senegalese grasshopper, Oedaleus senegalensis (Krauss 1877) to millet in the Sahel

Oedaleus senegalensis is a serious pest of millet in the Sahel, but the correlation to crop loss remains largely unknown. Therefore, the correlation between densities of O. senegalensis, defoliation level and millet yields was investigated in Niger in 2008, and a simple model to foresee the yield based on these parameters was developed. The yield was significantly correlated to both the density of O. senegalensis and the defoliation level on 17 September. The best model to foresee millet yield involved grasshopper density and cumulated rainfall and may be regarded a tentative method in O. senegalensis control.

The Biology of Senegalese Grasshopper (Oedaleus Senegalensis, Krauss, 1877) (Orthoptera: Acrididae)

The Senegalese grasshopper, Oedaleus senegalensis (Orthoptera: Acrididae) is known as pest of economic importance which cause damage to millet and sorghum crops besides pastures in western Sudan. The study was done to investigate the biology of the insect on its natural habitat. Observations in the field were made twice/ week, from April-November each year for three continuous seasons 2006/2007, 2007/2008 and 2008/2009, in two selected sites one around Gellabiya village in North Kordofan State west Elobeid town. The other was around Kuik village in South Kordofan State north Kadugli town. The nymphs and the adults were collected by sweep net from the field and transferred to the laboratory for study. Female adults of the Senegalese grasshopper were dissected and examined under binocular Microscope (Paralux, Optigue de précision CE 0602397) to investigate the fecundity through ovarioles numbers and function. Duration of each of the developmental stages of the pest was determined. Results showed that the mean number of ovarioles is 36 / ovary and two egg pods were laid /female. The mean fecundity was 44 eggs. The female laid eggs twice during life cycle. Ovariole function average was 76% in the first laying and 36% in the second laying. Mean developmental duration after hatching of O. senegalensis to adult (nymphal instars) was 25 day. The respective nymphal duration from the 1st to the 5th instar was 4, 5, 5, 5, and 6 days, respectively.

Insects associated with Jatropha curcas Linn. (Euphorbiaceae) in west Niger.

Jatropha curcas has been introduced into Niger since 2004 by International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). This plant is cultivated for its oil, which can be used as a Biofuel. Through direct and indirect insect collection methods, an inventory of the insect associated with J. curcas has been conducted in Western Niger during two rainy seasons (from June to October) in 2010 and 2011. We have identified insects belonging to the following families: Acrididae ( Oedaleus senegalensis Krauss , Oedaleus nigeriensis Uvarov, Heteracris leani Uvarov, Catantops stramineus Walker, Parga cyanoptera Uvarov, and Acanthacris ruficornis citrina Audinet-Serville), Pyrgomorphidae ( Poekilocerus bufonius hieroglyphicus Klug), Cetoniidae ( Pachnoda interrupta Olivier, Pachnoda marginata aurantia Herbst, Pachnoda sinuata Heinrich and McClain, and Rhabdotis sobrina Gory and Percheron), Meloidae ( Decapotoma lunata Pallas), Pentatomidae ( Agonoscelis versicoloratus Dallas, Nezara viridula Linn, and Antestia sp. Kirkaldy), Coreidae ( Leptoglossus membranaceus Fabricius and Cletus trigonus Thunberg), and Scutelleridae ( Calidea panaethiopica Kirkaldy). Origin and potential impact on J. curcas of all these insect species are presented and discussed. The lower insect’s diversity indexes are observed in 2010 and 2011 for Niamey, Saga, and Gaya because of semi-arid character of the Sahelian area.

Effect of cultural techniques: Rotation and fallow on the distribution of Oedaleus senegalensis (Krauss, 1877) (Orthoptera: Acrididae) in Senegal

The Senegalese grasshopper, Oedaleus senegalensis Krauss is a major pest in Sahel of West Africa. The present work reports the insect distribution and cultural techniques influence within two Senegalese localities. Methodology used is based on sampling and density estimates for a comprehensive study of Senegalese grasshopper in natural environment. Adult density was evaluated by visual counting on 100 m paths and larva density by counting one hundred sample surfaces of one square meter each. Sampling was conducted in fields of millet, bean, groundnut and fallows. The research work was performed for three consecutive years from 2006 to 2008. The Senegalese grasshopper distribution depends on biotope type, rainfall intensity and year. Its density was estimated monthly between 2 and 30 individuals per square meter. Larva density was significantly more abundant in fallow field than other fields. Crop rotation reduced density of Senegalese grasshopper and fallows favor the presence of the insect. These data suggest that field, rainfall intensity has an important effect of O. senegalensis distribution. Key words: Oedaleus senegalensis, density, cultures, rotation, fallow.

Studies on Population Dynamics of Senegalese Grasshopper (Oedaleus senegalensis) in Kordofan of Sudan

The Senegalese grasshopper (Oedaleus senegalensis) is a serious pest affecting cereal crops and grassy pastures in western Sudan. Intensive and extensive field’s surveys were conducted over a three-year period targeting O. senegalensis to study its ratio among other grasshopper species, in addition to its density and population structure/dynamics. Observations made twice a week, between April and November for three years (2006-2008) in two sites in Kordofan. Light traps installed in three selected areas to study nocturnal activity and migration every night from April to November for two seasons (2007/2008). The density assessed by visual counts of the nymph instars in 100 m² and adults in 1,000 m². The obtained data were analyzed using descriptive statistics. Results revealed that the Senegalese grasshopper is dominant over other grasshopper species and that the adults and nymphal instars appeared in two morphs: green and brown, according to prevailing environmental conditions. Mean population density was 1037 adult/ha and 3464 adult/ha in Kuik and Gellabiya sites, respectively; for nymphal instars, 2145 nymph/ha and 5500 nymph/ha, in Kuik and Gellabiya sites respectively.

Elements for the sustainable management of acridoids of importance in agriculture

Acridoidea is a superfamily within the Orthoptera order that comprises a group of short-horned insects commonly called grasshoppers. Grasshopper and locust species are major pests of grasslands and crops in all continents except Antarctica. Economically and historically, locusts and grasshoppers are two of the most destructive agricultural pests. The most important locust species belong to the genus Schistocerca and populate America, Africa, and Asia. Some grasshoppers considered to be important pests are the Melanoplus species, Camnula pellucida in North America, Brachystola magna and Sphenarium purpurascens in northern and central Mexico, and Oedaleus senegalensis and Zonocerus variegatus in Africa. Previous studies have classified these species based on specific characteristics. This review includes six headings. The first discusses the main species of grasshoppers and locusts; the second focuses on their worldwide distribution; the third describes their biology and life cycle; the fourth refers to climatic factors that facilitate the development of grasshoppers and locusts; the fifth discusses the action or reaction of grasshoppers and locusts to external or internal stimuli and the sixth refers to elements to design management strategies with emphasis on prevention.

Egg survival strategies of the Senegalese grasshopper during the dry season in the African Sahel

The Senegalese grasshopper is a major pest of crops in Sahelian Africa. It has three generations per year and undergoes a 7–8-month long embryonic diapause during the long dry season. Egg pods collected at the end of the rainy season from mid-August to the end of September (the known period of induction of the diapause) were placed in incubation in semi-natural conditions, and were humidified on various dates between November and August. The results reveal a rather complex diapause system, which is undoubtedly part of a bet-hedging strategy that is well adapted to maximizing overall survival and reproduction in the variable rains of the Sahel. In this strategy, some eggs hatch on early wet season rains and survive well if there is follow-up rain, while others remain in diapause and hatch when the wet season is assured.

Pathogenicity of the Fungus, Aspergillus clavatus, isolated from the locust, Oedaleus senegalensis, against larvae of the mosquitoes Aedes aegypti, Anopheles gambiae and Culex quinquefasciatus.

The use of insect pathogenic fungi is a promising alternative to chemical control against mosquitoes. Among the Hyphomycetes isolated from insects for mosquito control, the genus Aspergillus remains the least studied. In September 2005, four fungi were isolated from the Senegalese locust, Oedaleus senegalensis Kraus (Orthoptera: Acrididae), collected in Dakar, Senegal. One of these fungi, identified as Aspergillus clavatus, Desmazières (Eurotiales: Trichocomaceae) was highly pathogenic against larvae of the mosquitoes Aedes aegypti L., Anopheles gambiae s.l. Giles and Culex quinquefasciatus Say (Diptera: Culicidae). An application of 1.2 mg/ml dry conidia yielded 100% mortality after 24 hours against both Ae. aegypti and Cx. quinquefasciatus while with An. gambiae it was 95%. With unidentified species in the genus Aspergillus, mortality after 24 h was <5% against all the larval species. Application of A. clavatus produced in a wheat powder medium using doses ranging between 4.3 to 21×107 spores/ml, caused 11 to 68% mortality against Cx. quinquefasciatus at 24h, and 37 to 100% against Ae. aegypti. Microscopic observations showed fungal germination on both Ae. aegypti and Cx. quinquefasciatus larvae. Histological studies revealed that A. clavatus penetrated the cuticle, invaded the gut and disintegrated its cells. Some Cx. quinquefasciatus larvae, treated with A. clavatus reached the pupal stage and produced infected adults. However, the infection was mainly located on the extremity of their abdomen. These results suggest that A. clavatus could be an effective tool to manage mosquito proliferation.

Simulation studies of Senegalese Grasshopper ecosystem interactions I: the ecosystem model

I present a model that could simulate the ecosystem dynamics of the Senegalese Grasshopper (Oedaleus senegalensis, Krauss) in the Sahel. It included the migration of the grasshopper by simulating the population dynamics and migration in a number of locations along a south–north transect. The model ecosystem in each location comprised: (i) millet, (ii) a natural Sahelian grass representing the grassland vegetation, (iii) the Senegalese grasshopper; (iv) a less important grasshopper, Acrotylus blondlii, Saussure; (v) two species of grasshopper egg pod predators; and (vi) 24 species of birds that prey on grasshoppers. The model was rain-driven, used real climatic measurements as input, and was able to include the impact of grasshopper control measures such as treatment with chemical pesticides and the biopesticide Green Muscle®. The model has a wide variety of possible applications and may be used both for fundamental and applied purposes. Theoretic application may consist of investigating of the relative roles of natural egg pod predators and the many grasshopper-consuming bird species, as well as the ecological balance of a pest species that is under extensive natural control. Practical application may involve simulation of the impact of various control strategies, both on millet yield and the environment. Several simulations are presented to demonstrate the performance of the model, and to demonstrate the importance of the food web interactions, the temperature-dependent action of the biopesticide Green Muscle, and the importance of including the grasshopper migration in the model. One key result is that predation by the birds in the model might be replaced by a constant mortality rate without considerably changing the simulation of the population dynamics of O. senegalensi.

Simulation studies of Senegalese Grasshopper ecosystem interactions III: optimization of grasshopper control

Large tracts of millet fields in the Sahel are sprayed with chemical insecticides to control the grasshopper Oedaleus senegalensis, but it is difficult to assess the impact of these pesticide applications on the grasshopper's population dynamics due to its migratory behaviour. The grasshoppers migrate along a route which runs from south to north. Therefore, a simulation model that can simulate population development and migration on a simple south–north transect was used to assess the impact of treatment with pesticides, including the biopesticide Green Muscle®, in terms of grasshopper control on two south–north transects in the Sahel. The results indicate that the various actual pesticide treatments had a considerable overall impact on local grasshopper pressure but had little impact on sites further along the transect, because they were only carried out curatively in the millet fields themselves. The results however suggest that preventive treatment of both grassland and millet fields in the south would be more efficient, and thereby represents an alternative strategy. It would, moreover, appear that this could represent an environmentally sensitive alternative if carried out using Green Muscle, but even preventive use of a traditional chemical pesticide would be more environmentally sensitive than spraying pesticides solely on millet fields curatively and over a larger area.

Simulation studies of Senegalese Grasshopper ecosystem interactions II: the role of egg pod predators and birds

We present a simulation study of the role of birds and egg pod predators in the population dynamics of the Senegalese grasshopper. The model was an energetics-driven ecosystem model that included a natural Sahelian grass, millet, grasshoppers, the egg pod predators bombyliidae and Tenebrionidae, and 24 species of birds that prey on grasshopper nymphs and adults. The model simulated the rain-dependent dynamics and migration along a five-location south–north transect in Niger and Senegal, and the main outputs were the grasshopper pressure on the transect, measured as accumulated transect grasshopper days, and the density of eggs ready to emerge the following rainy season. The model was calibrated using observations from transects in Niger (2003, 2004) and Senegal (2004). When input data from Niger 2003 and 2004 were applied, simulated reductions in grasshopper pressure during the rainy season from egg pod predators and birds, respectively, were within a range of 18–25%, but taken together the overall reduction in grasshopper pressure ranged between 35 and 37%. Using input from Senegal (2004) the birds accounted for reductions of around 25%. When the impact of the natural enemies was measured in terms of reduction in the density of eggs hatching the following year, the simulated impact of the egg pod predators ranged between 45 and 83% and that of the birds between 33 and 39%, and the two groups combined caused reductions between 60 and 75%. Analyses of the sensitivity to the bird species, added one by one, showed ‘predator saturation’ along the Niger transects (with low grasshopper density) but not along the Senegal transect. For Niger, the sensitivity analyses revealed Cattle Egret, Grey-headed Sparrow, Chestnut-bellied Starling, Buffalo Weaver, Sudan Golden Sparrow, Grey Hornbill, Red-billed Hornbill and Abyssinian Roller to be the most important individual species. For Senegal the top-five individual bird species were Village Weaver, Buffalo Weaver, Savile's Bustard, Grey-headed Sparrow and Abyssinian Roller.

Application of mixtures of Metarhizium anisopliae var. acridum and cyhalothrin against the Senegalese grasshopper in Senegal

From 2002 to 2004, three field trials were conducted in Senegal to compare the efficacy of a new biopesticide for grasshopper control, based on the entomopathogenic fungus Metarhizium anisopliae var. acridum Driver & Milner, with mixtures of this biopesticide and cyhalothrin, a widely used pyrethroid insecticide to control the Senegalese grasshopper Oedaleus senegalensis Krauss. The aim of these trials was to obtain a knockdown effect without compromising the environmental credentials of the biopesticide too much. During the first two trials, 50 ha (2002) and 25 ha (2003) plots were treated with Metarhizium at a rate of 50 g/ha, cyhalothrin at a rate of 40 g/ha, a mixture of Metarhizium at a rate of 25g/ha and cyhalothrin at a rate of 20g/ha. For the third trial in 2004, several mixtures of cyhalothrin at a rate of 10 g/ha and Metarhizium at dose rates of 6.25,12.5 and 25g/ha were prepared. These mixtures were compared with 50 g/ha of Metarhizium, 40 g/ha of cyhalothrin and 10 g/ha of cyhalothrin on 25 ha experimental plots. The volume application rate for all trials was 1 l/ha. The Metarhizium applications resulted in a slow but long-lasting reduction of grasshopper numbers. By contrast, cyhalothrin produced a rapid reduction, but grasshopper numbers re-increased a few days after application, except in 2003, when grasshopper densities in the surrounding areas were low. The mixtures caused a similarly fast reduction in grasshopper numbers, but this lasted throughout the 3 week post-application assessment period. These trials demonstrated that adding a low dose of a pyrethroid insecticide to a slow-acting biopesticide can increase the speed of population reduction, while retaining the latter’s long-lasting effect. A bonus is that the price of the combination is lower than that of each product at the recommended dose rates. Since the insecticide is added at a low dose, its environmental impact is reduced compared with the full-dose insecticide only treatment.

Abdim’s Stork Ciconia abdimii Exploitation of Senegalese Grasshopper Oedaleus senegalensis in South-eastern Niger

Abstract Abdim’s Storks Ciconia abdimii were studied in a post-breeding staging area dominated by Sahelian grasslands in southeastern Niger. In late September 2003, a total of 5,763 birds was recorded on systematic transect counts. The estimated density was 5.66 per km2, equivalent to a total of c. 17,000 Abdim’s Stork within the utilized area of 3,000 km2. A high percentage of juveniles in the flocks in late August, when the Nigerien breeding population is still at their nests, indicate a southern origin of the birds. The storks probably make northward post-breeding movements into the Sahel to feed on locally abundant food supplies, first of all Senegalese Grasshopper Oedaleus senegalensis, the dominant grasshopper species in the area. The mean density of Oedaleus in late September 2003 was 11.2 per m2 (6.7 g fresh weight/m2). Storks feeding on grasshoppers made on average 5.6 successful pecks per min during their first h of daily feeding, enabling them to fulfil 95% of their daily energy requirements wi...

Ecology and management of the Senegalese grasshopper Oedaleus senegalensis (Krauss 1877) (Orthoptera: Acrididae) in West Africa: review and prospects

Following the droughts that occurred in the Sahel during the 1970s, the Senegalese grasshopper Oedaleus senegalensis (Krauss 1877) suddenly became the main pest grasshopper species in this region, where it regularly causes serious damage to crops, especially millet. The lifecycle of O. senegalensis reflects the precariousness of the Sahelian environment. The lifecycle and survival strategies of O. senegalensis have evolved to include migration following shifts in the intertropical convergence zone (ITCZ) and embryonic diapause in the dry season. It is thus able to cope with its natural hostile environment and remain in the most suitable ecological conditions for as long as possible. The alternation between outbreaks and recession periods seems to be related to the high spatiotemporal rainfall variability in the Sahel. Senegalese grasshopper outbreaks depend on the rainy season chronological pattern and on the initial quantity of diapaused eggs in the soil. Since the 1970s, many studies have been conducted on this species in the Sahel. Various models designed to monitor the population dynamics of this species have been published. However, some key factors that could explain the variability in outbreaks have not been seriously investigated. The present bibliographical review provides an overview on current knowledge while proposing some avenues for future research to enhance the sustainable management of this major Sahelian pest.