D. Seck

Alternative protection of cowpea seeds against Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) using hermetic storage alone or in combination with Boscia senegalensis (Pers.) Lam ex Poir

Abstract The effect of hermetic storage alone or in combination with Boscia senegalensis has been evaluated against Callosobruchus maculatus . Analysis of gas concentrations within a 7-day period indicated that O 2 declined from 19.2 to 2.3% and CO 2 rose from 1.2 to 22.8%. Prolonged storage durations increased adult mortality, significantly increased the developmental time and induced 60–80% reduction in the F1 progeny. The use of hermetic storage in combination with B. senegalensis fruits, at 1.2 g/l (flask volume) reduced the emergence of the cowpea beetle, while 2.4–4.8 g/l completely inhibited the production of a new generation of C. maculatus .

Biological activity of the shrubBoscia senegalensis (PERS.) LAM. ex Poir. (Capparaceae) on stored grain insects

Biological activity of leaves, fruits and extract of the African shrubBoscia senegalensis (PERS.) LAM. ex Poir. was evaluated against five stored-grain insects. When added to cowpeas at 2–4% (w/w), fresh ground fruits and leaves caused 80–100% mortality inCallosobruchus maculants (F.) adults and significantly reduced both emergence and damage of the F1 progeny. Acetone fruit extract exhibited a potent fumigant effect onProstephanus truncatusHorn, C.maculatus, andSitotroga cerealella OLIV.; with LT50 values of 3.8, 2.3, and below 1.5 hr, respectively. LC50 determination forB. senegalensis fruits and leaves as well as pure methylisothiocyanate (MITC) onTribolium castaneum HERBST,Sitophilus zeamais MOTSCH. andC. maculatus showed a differential response of the insects to plant parts or MITC. Quantitative dosage ofBoscia active components and LC50 values obtained for the plant tissues, compared to those of pure molecules, indicate that the biological activity ofB. senegalensis is due to the liberation of MITC from a glucosinolate precursor glucocapparin contained inBoscia fruits and leaves.

Passive sampling devices enable capacity building and characterization of bioavailable pesticide along the Niger, Senegal and Bani Rivers of Africa

It is difficult to assess pollution in remote areas of less-developed regions owing to the limited availability of energy, equipment, technology, trained personnel and other key resources. Passive sampling devices (PSDs) are technologically simple analytical tools that sequester and concentrate bioavailable organic contaminants from the environment. Scientists from Oregon State University and the Centre Régional de Recherches en Ecotoxicologie et de Sécurité Environnementale (CERES) in Senegal developed a partnership to build capacity at CERES and to develop a pesticide-monitoring project using PSDs. This engagement resulted in the development of a dynamic training process applicable to capacity-building programmes. The project culminated in a field and laboratory study where paired PSD samples were simultaneously analysed in African and US laboratories with quality control evaluation and traceability. The joint study included sampling from 63 sites across six western African countries, generating a 9000 data point pesticide database with virtual access to all study participants.

Biological activity of Cassia occidentalis L. against Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Abstract In developing countries, traditional control methods are commonly used against stored-product insects and mites. In Senegal, the leaves of Cassia occidentalis L. (Caesalpiniaceae) are used to protect cowpea seeds (Vigna unguiculata L. (Walpers)) against Callosobruchus maculatus (Coleoptera: Bruchidae). The biological activity of the leaves, the seeds and oil of C. occidentalis was evaluated in controlled conditions (28 ± 2°C, 45 ± 5% r.h.) against C. maculatus. At the rate of 10% (w/w), both fresh and dry leaves as well as whole and ground seeds had no contact toxicity on the cowpea beetle. In contrast, seed oil induced an increase in mortality of C. maculatus eggs and first larval instar at the concentration of 10 ml/kg cowpea. The basis of the ovicidal and larvicidal activities are discussed in this paper. Several trials using pure compounds have highlighted that several fatty acids (linoleic, oleic and stearic) are responsible for C. occidentalis toxicity. C. occidentalis seed oil did not reduce the oviposition of C. maculatus at 10 ml/kg seed.

Insecticidal activity of Boscia senegalensis (Pers.) Lam ex Poir. on Caryedon serratus (Ol.) pest of stored groundnuts

Institut de Technologie Alimentaire, Hann-Dakar, BP 2765, Senegal. Centre Regional de Recherche en Ecotoxicologie et Securite Environnementale (CERES/Locustox), km 15 Route de Rufisque, BP 3300 Dakar, Senegal. CIP (International Potato Center) – BP 08 0932Cotonou, Benin. Departement de Biologie Animale, Faculte des Sciences de Dakar, UCAD, BP 5005, Dakar, Senegal. Universite de Liege, Gembloux Agro-Bio Tech, Unite de Chimie Generale et Organique, 2 Passage des Deportes -5030 Gembloux, Belgique. Universite de Liege, Gembloux Agro-Bio Tech, Unite de Chimie Analytique, 2, Passage des Deportes -5030 Gembloux, Belgique.

Efficacy of powdered maize cobs against the maize weevil Sitophilus zeamais (Coleoptera: Curculionidae) in stored maize in Senegal

Powdered maize cobs were tested as an alternative for pesticide use in stored maize. Five doses (2, 4, 6, 8 and 10 g/250 g seed) of powdered maize cobs applied at particle sizes of 1.4 and 0.4mm diameter were compared with actellic powder against Sitophilus zeamais Motschulsky for 120 days. Mortality and survival data showed that cob powders did not act as fumigant but exerted a potent inhibition of progeny on direct contact with S. zeamais adults. The particle size of powdered cobs had no effect on maize damage and losses. At doses equal to or higher than 6 g powdered maize cobs/250 g grain maize, i.e. 2.4% (w/w), damage to grain was < 5% and weight losses < 1%. The protection offered at the highest dose was comparable to the pesticide control. The use of powdered maize cobs is discussed as a natural alternative to synthetic pesticides for protection of maize against S. zeamais.

Analysis of the Composition of Plant Essential Oil Used in Cereals and Legumes Storage in Senegal

Abstract Chemical composition of Hyptis spicigera, H. suaveolens and Eucalyptus camaldulensis essential oils isolated by hydrodistillation of plant leaves from Senegal were determined by GC-MS / GC-FID. A total of twenty-nine, thirty-seven and thirty-four components were identified for H. spicigera, H. suaveolens and E. camaldulensis, respectively. H. spicigera oil contained as main components α-pinene (38.9 %), β- pinene (14.7 %) and caryophyllene (12.6 %). For H. suaveolens we obtained at first, in February 1,8-Cineole (19.8%), caryophyllene (16.9 %) and sabinene (11.6% ); at March, sabinene and caryophyllene represented 27.9 % and 20.8 % respectively while 1,8-Cineole decreased from 19.8 to 1.1%. The most important component revealed with E. camaldulensis were spathulenol (31.6 %), p-cymene (11.3 %), bicyclogermacrene (8.2 %) and β-selinene (7.9 %).

Growth-inhibiting effects of a neem-based insecticide (Margosan-O) against Spodoptera littoralis (Lepidoptera: Noctuidae

Margosan-O®, a commercial neem-based insecticide, incorporated into an artificial diet prolonged the development of larvae of Spodoptera littoralis Boisduval. It also affected the rate of adult emergence at the end of pupation. Larvae treated during one stadium continued to show the effects of their previous exposure. The susceptibility to Margosan-O was more pronounced when larvae ate the diets containing Margosan-O for the first time during the fifth or sixth instar. The results indicate that Margosan-O has an activity similar to that of other neem-seed extracts. In the course of this work morphological anomalies were also recorded. The most striking was the appearance of black stripes on the abdominal tergites of the fifth and sixth instar larvae fed on diets containing 0.01, 0.05 or 0.1% of Margosan-O.RésuméUn insecticide commercial à base d’azadirachtine (Margosan-O®), incorporé à la nourriture artificielle, a prolongé la durée de développement des larves de Spodoptera littoralis Boisduval. Il a également affecté le nombre d’émergence d’adulte à la fin du stade nymphale. Les larves traitées pendant un stade donnée continuaient à manifester les effets de leur exposition au substrat. La sensibilité du Margosan-O était plus importante lorsque les larves se nourrissaient d’un substrat contenant Margosan-O au cours du cinquième et sixième stade. Les résultats montrent que le Margosan-O a la même activité que d’autres extraits à base de neem. Cet insecticide provoque également chez Spodoptera littoralis des anomalies morphologiques au cours des stades de développement; des bandes noires apparaissent sur les tergites abdominales lorsque les larves du cinquième et du sixième stade se nourrissent d’un substrat contenant 0.01, 0.05, ou 0.1% de Margosan-O.

Etude de l'infestation initiale de Sitotroga cerealella Oliv. (Lepidoptera, Gelechiidae) en function de la localisation des champs de mil, Pennisetum typhoides (L) Leeke

RésuméL’infestation au champ de Sitotroga cerealella (infestation primaire) a été etudiée dans 2 conditions de culture du mil et dans 3 localités du Sénégal. Dans toutes les conditions, les épis sont attaqués des la récolte mais les dégâts sont 10 fois plus importants sur les épis des champs de case que sur ceux des champs éloignes des villages. Ainsi, l’auteur pose la problèmatique de la conservation des semences de mil en milieu paysan liée d’une part à cette infestation, et d’autre part à la méthode de conservation des épis en greniers traditionnels.AbstractField infestation of millet by Sitotroga cerealella (initial infestation) has been studied in two cropping systems and in three locations in Senegal. In all cases, ears were attacked since harvest, but the level of damage was 10 times higher on ears from fields close to dwelling houses than on those away from dwelling houses. In this way, the author discusses the problematic conservation of millet seeds in farm conditions, depending on that initial infestation in one hand and on the other hand on storage method of millet ears in traditional granaries.