Influence des zones agroécologiques sur les paramètres biologiques de Callosobruchus maculatus (Coleoptera-Bruchidea), ravageurs des graines du niébé (Vigna unguiculata Walp.) au Niger

Au cours de cette étude, les paramètres biologiques de Callosobruchus maculatus provenant de différentes zones agro-écologiques du Niger sont déterminés. Pour cela, des souches de C. maculatus ont été collectées dans 4 localités représentant chacune une zone agro-écologique. L’analyse des résultats obtenus montre que quelle que soit la souche, la longévité des adultes de cette espèce ne dépasse guère 7 jours. Par contre, la fécondité est significativement plus importante pour les souches provenant de la zone sahélienne que pour celles provenant des autres zones  agroécologiques. Par ailleurs, L’évolution des pontes montre que quelle que soit la souche, plus de 96% des oeufs sont pondus pendant les  quatre premiers jours de l’infestation. En outre, les souches se  caractérisent par un taux de fertilité des oeufs relativement important et une durée d’éclosion des oeufs peu variable. La durée de développement est relativement plus élevée chez les souches de la zone du fleuve (33 jours) que chez celles de la zone saharienne et sahélienne (30 jours). Le taux de survie larvaire et le taux d’émergence sont plus importants pour les souches de la zone sahélo-soudanienne (Gaya) et sahélienne (Tarna) que pour celles originaires des zones saharo-sahélienne et saharienne.Mots clés: Niébé (Vigna unguiculata), Callosobruchus maculatus,  Paramètres biologiques, zones agroécologiques, Niger

Influence de Boscia senegalensis (Pers) Lam. Ex Poir. (Capparaceae) sur les capacités de dispersion de Dinarmus basalis Rond. (Hymenoptera- Pteromalidae) dans les systèmes de stockage traditionnels de niébé

Impact of Boscia senegalensis (Pers) Lam. Ex Poir. (Capparaceae) on the Dispersion Capacities of Dinarmus basalis Rond. (Hymenoptera- Pteromalidae) in Traditional Storage System. In this study, the impact of Boscia senegalensis (Pers) Lam. Ex Poir. (Capparaceae) on dispersion capacities of Dinarmus basalis Rond (Hymenoptera-Pteromalidae), a solitary ectoparasitoïd of the development stages of bruchid pests of cowpea (Vigna unguiculata (L.) Walp), within a traditional storage system is analysed. The results point out that, whatever the position of the treated patch, females of D. basalis are able to move between seeds of cowpea and some of them are able to localize and parasitize their hosts. In a non choice situation, the rates of parasitism observed were less important than the ones obtained when the patchs were not treated with B. senegalensis. Nevertheless in situation of choice, females seem to avoid the patch treated with the insecticidal plant B. senegalensis

Etude de quelques facteurs influençant la biologie et le comportement de Bruchidius atrolineatus Pic. (Coleoptera-Bruchinae), ravageur du niébe(VIGNA UNGUICULATA (L.) Walp en zone sahelienne

Bruchidius atrolineatus Pic. est le principal ravageur du niébé en culture et en début de stockage. Au cours de cette étude, certains facteurs susceptibles d’influencer sa biologie, son développement et son comportement dans les cultures de niébé ont été étudiés. Pour ce faire, l’influence de l’alimentation des adultes de cet insecte à base de fleurs de trois espèces végétales, à savoir Balanites aegyptiaca, Neocarya macrophylla, Acacia seyal et Bauhinia rufescens sur sa durée de vie d’une part et, d’autre part, les paramètres biologiques et la capacité de discrimination de l’insecte en présence de trois variétés de niébé (une variété locale, KVX et HTR) ont été étudiés. Pour tous les paramètres étudiés, l’expérience est réalisée avec des insectes âgés d’au plus 24 h. L’analyse des résultats obtenus montre que la durée de vie est prolongée de 02 à 08 jours lorsque les insectes sont nourris comparativement au témoin négatif. Pour le témoin positif qui a consisté à nourrir les insectes d’eau saccharosée, la durée de survie est de 35 jours. Par ailleurs, l’activité de ponte de B. atrolineatus est relativement influencée par la taille des graines de la variété. En effet, les résultats révèlent que plus la taille de la graine est importante plus le nombre d’oeufs déposés est élevé. Le taux de survie larvaire et le taux d’émergence des adultes sont plus faibles sur les graines des variétés améliorées que sur celle de la variété locale. Ainsi, les facteurs comme l’alimentation au dépend des fleurs et les variétés de niébé utilisées influencent la biologie, le développement et le comportement de B. atrolineatus.Mots clé : Bruchidius atrolineatus, niébé, paramètres biologiques, alimentation , capacité de discrimination.English AbstractStudy of some factors influencing the biology and behavior of  Buchidius atrolineatus pic.(Coleoptera-bruchinae), pest of cowpea (Vigna unguiculata (l.) Walp in the Sahelian zoneBruchidius atrolineatus Pic. is the main pest of Cowpea in field and beginning of storage. Some factors that may influence its biology, its development and its behavior in Cowpea field were studied. So the influence of the diet of this species based on flower on its life duration on one hand and, on the other hand, the biological parameters and discrimination ability of the insect in the presence of three cowpea varieties have been studied. The analysis of the results obtained shows that the life duration is extended from 02 to 08 days when the insects are fed compared to the negative control. For the positive control fed on water saccharosee, the survival time is 35 days. Otherwise, the ovipositor activity of B. atrolineatus is relatively influenced by the size of the seeds of the variety. Indeed, the results show that more the size of the seeds is important more the number of eggs laid is high. Larval survival and adult emergence rate are lower on the seeds of  improved varieties than on the local variety. Factors like flowers and varieties influence biology, development and behaviour of B. atrolineatus.Keywords : Bruchidius atrolineatus, cowpea, biological parameters, power; capacity of discriminat

Parasitism of Locally Recruited Egg Parasitoids of the Fall Armyworm in Africa

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an insect native to the tropical and subtropical Americas that has recently spread to Africa, where it predominately attacks maize, sorghum and other plant species. Biological control is an environmentally friendly way of combatting the pest and contributes to an integrated pest management approach. In Africa, several trichogrammatid parasitoids and Telenomus remus Nixon (Hymenoptera: Platygastridae) have been found parasitizing eggs of the FAW. In Niger, the egg parasitoids encountered include Trichogrammatoidea sp. (Hymenoptera: Trichogrammatidae) and Telenomus remus Nixon. Parasitism of the FAW eggs by the two egg parasitoids was assessed in the laboratory, followed by field testing on sentinel eggs. In the laboratory, T. remus parasitized on average 78% of FAWeggs, compared to 25% for Trichogrammatoidea sp. Telenomus remus was able to parasitize egg masses that were fully covered with scales, while Trichogrammatoidea sp. parasitized only uncovered egg masses. On-farm releases of T. remus in sorghum fields caused up to 64% of FAW egg parasitism. Parasitized eggs yielded viable progeny, which can contribute to FAW egg parasitism build-up during the cropping season. Our findings lay the groundwork for the use of T. remus in augmentative releases against FAW in Africa

Toxicity and persistence of Boscia senegalensis Lam. (Ex Poir.) (Capparaceae) leaves on Callosobruchus maculatus Fab. (Coleoptera:Bruchidae)

In this study, we examined the toxicity and persistence of ground fresh leaves of B. senegalensis on the development of Callosobruchus maculatus, major insect pest of cowpea (V. unguiculata) in the sahelian area. The effect of the product has been evaluated over the three developmental stages (egg, larvae and adult) of C. maculatus. At high concentration (4 g/l of ground leaves), 100 % of adults were killed within 24 h of exposure to the leaf extract, and the development of newly laid eggs and neonate larvae was also inhibited. However, the ground leaves of B. senegalensis have a variable efficacy against the bruchid instars larva. The 2nd larvae stage (L2) of C. maculatus developing inside the seeds have proved to be highly susceptible while the 4th larval stage was relatively tolerant. The study of the toxicity persistence of the leaves of B. senegalensis showed that whatever its concentration, the efficacy of crushed leaves of B. senegalensis decreased with the storage time. At a concentration of 20 g/l, the effect of B. seneglensis can persist up to 7 days.Keywords: Biopesticides, Bruchids, cowpea, pest control, Nige

Physic nut (Jatropha curcas) oil as a protectant against field insect pests of cowpea in Sudano-Sahelian cropping systems

Cowpea is a profitable food and fodder crop in the Sudano-Sahelian region of Africa. Unfortunately, it is extensively damaged in the field by a range of insect pests. The use of locally available insecticidal plant extracts is a promising alternative to chemical crop protection, which is the most popular management strategy but shows many drawbacks. In this respect, oil extracted from seed of the physic nut shrub (Jatropha curcas) showed promise. The insecticidal properties of J. curcas oil were thus assessed against cowpea insect pests at the ICRISAT research station, Sadoré, Niger. In 2002, four concentrations of physic nut oil extract, formulated as an emulsifiable concentrate (EC) (namely 2.5%, 5%, 7.5% and 10%), were evaluated as field sprays along with an untreated control (water spraying) and a conventional insecticide (Deltamethrin Decis® EC) treatment. In 2009, these latter two checks were evaluated alongside four concentrations of a “blank” formulation consisting of only the adjuvants of the 2002 EC formulation (namely 1.25%, 2.5%, 3.75% and 5%). In 2002, application of Deltamethrin and physic nut oil at 7.5% gave the highest seed yields, with more than 1000 kg ha-1. Both treatments, alongside the one with 10% oil, sustained significantly lower thrips (Megalurothrips sjostedti) infestation than the water-sprayed control. All oil extract treatments and the Deltamethrin treatment sustained significantly lower infestation by Clavigralla tomentosicollis bugs than the untreated control, with the lowest infestation occurring with 7.5% oil. Furthermore, correlations between oil concentration and thrips and bug infestation were negative and significant, while correlation between oil concentration and seed yield was not significant, due to a phytotoxic effect of oil at high concentrations. The follow-up studies in 2009 confirmed that effects of Jatropha oil on cowpea insect infestation and seed yield observed in 2002 could be ascribed to the physic nut oil fraction alone

Evolution des populations des champignons endomycorhiziens sur les adventices de quatre sites maraîchers de la région de Maradi au Niger

Le rôle important que jouent les endomycorhizes dans l’amélioration de la nutrition minérale et la protection des plantes est aujourd’hui largement reconnue. Cependant dans des pays comme le Niger, peu de travaux leur ont été consacrés. Cette étude a été conduite pour évaluer la mycorhization dans les parcelles de poivron pendant la contre-saison afin de connaitre le moment opportun de les récupérer dans le but de les utiliser ultérieurement dans des programmes de développement des cultures maraichères. Des échantillons de sol et de racines ont été prélevés dans 4 sites sur les 9 principales adventices du poivron. Ils ont été analysés au laboratoire et la densité des spores et l’intensité de l’infection ont été déterminées. Ces deux paramètres ont varié d’un site à l’autre et d’une plante à l’autre. Cinq espèces d’endomycorhizes à vésicules et arbuscules ont été identifiées dont 3 appartenant au genre  Glomus et 2 au genre Gigaspora. Acanthospermum hispidum et Solanum nigrum ont été les plantes les plus infectées. Sur les 6 mois de l’étude, les plus fortes densités de spores et d’intensité d’infection ont été enregistrées entre décembre et janvier et les plus faibles en mars.Mots clés : Endomycorhizes, dynamiques des populations, cultures maraichères, Niger

Effets de Boscia senegalensis (Pers.) Lam. Ex Poir. (Capparaceae) sur l'évolution des populations de bruches dans les systèmes de stockage traditionnel de niébé (Vigna unguiculata (L.) Walp) en zone sahélienne

Effects of B. senegalensis (Pers.) Lam. Ex Poir. (Capparaceae) on Bruchids Populations within Storage Traditional System of Cowpea beans (Vigna unguiculata (L.) Walp) in Sahelian Area. Bruchidius atrolineatus Pic. (Coleoptera- Bruchidae) and Callosobruchus maculatus Fab. (Coleoptera-Bruchidae) are, in Sahelian area, the most important pests of cowpea beans, (Vigna unguiculata (L.) Walp). Cowpea infestation by these two species of bruchids starts in the field at the beginning of the plant fruit bearing and continues during storages where damage can be high if no control action is taken. In this study, the impact of several introductions of B. senegalensis (Pers.) Lam. Ex Poir. (Capparaceae), an insecticidal plant which is usually used by farmers in Niger, on the population dynamics of the two bruchids species in traditional cowpea storage system has been investigated. The results obtained from this study point out that bruchid populations are more important in the standard jars than in the one, which have received regular inputs of B. senegalensis. Thus, preservation action by regular inputs of B. senegalensis seems to be an efficient way to control bruchids in the cowpea traditional storage system

Effect of solar drying on the biological parameters of the cowpea weevil, Callosobruchus maculatus Fab. (Coleoptera-Bruchinae), in Sahelian area.

Objective: Callosobruchus maculatus Fab. (Coleoptera: Bruchinae) is a major pest of cowpea seeds (Vigna unguiculata (L.) Walp) in the Sahelian zone. The grain infestation by this insect pest starts in the field at the beginning of fructification of the plant and continues in storage where the damage can be significant if no protective measures are taken. In order to prevent the damage caused by C. maculatus in storage of cowpea, farmers commonly expose the seeds and pods to the sun radiations for several days before storing them. Therefore, the aim of this study is to investigate the impact of sun radiation on the egg laying and development of weevils in general and particularly C. maculatus.Methodology and results: To achieve this goal, experiments were conducted to determine the biological parameters of two batches of this pest respectively exposed to sun radiations and in the laboratory environment. The investigated parameters include longevity, fertility, infertility rate, eggs, development time, larval survival rate and emergence rate. This study results indicated that the different biological parameters studied were significantly affected when the insects were reared under sun radiations. In fact, it appears under this study experimental conditions that sun exposure significantly inhibits egg laying, embryonic development and postembryonic development of C. maculatus resulting in complete inhibition of the emergence of the offspring.Conclusion and application of results: Thus, solar drying seems to be an effective method of preventing weevil damage during cowpea storage.Keywords: Cowpea; Callosobruchus maculatus; solar drying; Sahelian area