Impact of African Weaver Ant Nests [Oecophylla longinoda Latreille (Hymenoptera: Formicidae)] on Mango [Mangifera indica L. (Sapindales: Anacardiaceae)] Leaves

Oecophylla ants are appreciated for their control of pests in plantation crops. However, the ants´ nest building may have negative impacts on trees. In this study we tested the effect of ant densities and nest building on the leaf performance of mango trees. Trees were divided into three groups: trees without ants, trees with low and trees with high ant densities. Subsequently, the total number of leaves, the proportion of leaves used for nest construction, and tree growth was compared between these groups. The percentage of leaves used for nests was between 0.42-1.2 % (mean = 0.7%±0.02) and the total number of leaves and tree growth was not significantly different between trees with and without ants. Further, leaf performance was compared between shoots with and without ant nests and between leaves in or outside ant nests. The number of leaves and lost leaves per shoot, leaf size, leaf condition (withered), leaf longevity and hemipteran infection was compared between groups. In the dry season nest-shoots held more leaves than shoots without nests despite nest-shoots showed more lost leaves. Leaves in nests were smaller than other leaves, more likely to wither and more often infested with scales. However, smaller nest-leaf size was probably due to the ants´ preference for young leaves and the higher incidence of withering resulting as leaves in nests cannot fall to the ground. In conclusion, the costs associated to ant nests were low and did not affect the overall number of leaves per tree nor tree growth

Effectiveness of neem seed oil (Azadirachta indica A. Juss: Meliaceae) on Syllepte derogata Fabricius, Lepidoptera: Pyralidae

Objective: Synthetic insecticides have long been used for cotton protection,  resulting in pest resistance, toxicity and environmental pollution. Biopesticides have been suggested as alternatives to synthetic pesticides. Both field and laboratory experiments were conducted to evaluate the effectiveness of neem oil in controlling Syllepte derogata (Fabricius), a cotton phyllophagous pest.Methodology and Results: In the field trials, effect of neem oil was compared to that of conventional insecticides; while in the laboratory direct larval immersion and leaf dip method using EMA SUPER 56DC and neem oil were tested. Decrease in damage by S. derogata for about 63 and 86% was recorded with neem oil and synthetic insecticides. In the laboratory, the mortality of S. derogata after 24 hours exposure to neem oil and Ema Super was significantly higher (2.5 to 100%) than that of the control. The mortality of larvae of S. derogata was positively correlated with the concentration of neem oil and exposure time. Lethal Concentration (LC50) after 24 hours exposure of larvae was respectively 4.03 104 ml/l and 51.13 ml/l forleaf dipping method and larval immersion.Conclusion and application of results: Overall, these results showed the efficacy of neem oil in controlling S. derogata, as a biopesticide. This oil could also  constitute a successful alternative to synthetic pesticides. However, the  effectiveness of neem oil appeared to be weakened by the rapid degradation of the active substances, azadirachtin in particular. Indeed, azadirachtin, the main active ingredient of neem is photo and heat labile. It easily degrades under high solar radiations and high temperatures, hence the need for stabilization.Keywords: Phyllophagous pest, integrated pest management, leaf-dipping method, larval immersion, Lethal Concentration

Indigenous cowpea production and protection practices in Benin

A survey involving more than 129 farmers was carried out in 1998 and 1999 in Ouémé, Benin, to investigate the importance of pests and diseases as constraints to cowpea (Vigna unguiculata (L.) Walp.) production. Results indicated that in the Ouémé valley Sclerotium rolfsii Sacc. and Aphis craccivora Koch are specific concerns. Weeds such as Justicia anselliana (Nees) T. Anders, Ipomoea aquatica Forsskal and Commelina erecta L. were also reported as being troublesome. On the Ouémé plateau Imperata cylindrica L. Beauv. was reported to be a major weed. Callosobruchus maculatus Fab. and Bruchidius atrolineatus Fab. may cause up to 100% loss within a few months in storage. Birds and rodents were also reported. In certain areas on the plateau, farmers have developed pest control methods based on indigenous knowledge. In the valley the population density of Eichhorniacrassipes (Mart) Solms. during flooding is used by farmers to predict aphid infestation. A number of plant species used to protect cowpea were reported. In Gbékandji village, natural enemies such as Rhabdepyris sp., Evania sp., and Chelonus sp., were observed. They were rare in the valley, where farmers rely on chemical control. Farmers reported alternative hosts of cowpea pests from the families Fabaceae (eight species), Mimosaceae (two species), Ceasalpiniaceae (five species), Capparidaceae (two species) and Pontederiaceae (one species). Based on the hierarchy of constraints, sustainable integrated pest management technologies are being developed with farmers using a participatory approach. RÉSUMÉ Bien que des options de lutte existent, les ravageurs et les maladies demeurent la principale contrainte à la production du niébé (Vigna unguiculata (L.) Walp.). Les problèmes phytosanitaires du niébé ont fait l'objet d'enquêtes menées en 1998 et 1999 auprès de plus de 129 paysans dans la vallée et sur le plateau du département de l'Ouémé au Sud Bénin. Les résultats montrent que dans la vallée, Sclerotium rolfsii Sacc. et Aphis craccivora Kock sont des préoccupations spécifiques. Les mauvaises herbes: Justicia anselliana (Nees) T. Anders, Ipomoea aquatica Forsskal et Commelina erecta L. y sont préoccupantes. Imperata cylindrica L. Beauv. est la plus nuisible sur le plateau. Callosobruchus maculatus Fab. et Bruchidius atrolineatus Fab. peuvent occasionner 100% de perte en quelques mois de stockage. Les oiseaux et les rongeurs ont été signalés. Dans certaines zones du plateau, des paysans ont développé des méthodes de protection basées sur des connaissances endogènes. Selon les paysans de la vallée, la densité de peuplement d'Eichhornia crassipes (Mart) Solms. pendant l'inondation permet de prédire l'infestation de pucerons. Des plantes à effet insecticide ont été signalées. Dans le village de Gbékandji, des ennemis naturels: Rhabdepyris sp., Evania sp., et Chelonus sp., etc. ont été observés. Ils étaient rares dans la vallée où l'utilisation de produits chimiques est prononcée. Les paysans ont rapporté des hôtes alternatifs des déprédateurs de niébé de la famille des Fabaceae (08 espèces), Mimosaceae (02 espèces), Ceasalpiniaceae (05 espèces), Capparidaceae (02 espèces) et Pontederiaceae (01 espèce). Se basant sur la hiérarchisation des contraintes, des méthodes participatives de mise au point de technologies durables de lutte intégrée sont en cours d'élaboration

Cytotoxic activities of sterols and triterpens identified by GC-MS in justicia anselliana (NEES) T. anders active fractions and allelopathic effects on cowpea (Vigna unguiculata (L.) Walp) plant

Purification of the allelopathic ethanol extract of Justicia anselliana aerial part led to actives purification fractions. GC-MS analysis of these fractions helped to identified ten known compounds: five sterols (campesterol; stigmasterol; β-sitosterol acetate; 9,9-cyclolanostan-3-ol, 24-methylene; 9, 19-cyclolanost-24-en-3-ol), two triterpens (α – amyrin; lupeol), a diterpene (phytol) and two derivatives of alcane(heneicosane; ethyl palmitate). Eight of these compounds are reported for the first time on Justicia anselliana. Identification compounds were tested for their allelopathic effects on cowpea (Vigna unguiculata) growth and for their cytotoxic activity on human (HeLa, WI-38 and Mel-43) and mouse (J774)cells. All tested compounds showed an inhibitory effect on the three parameters measured on cowpea (Vigna unguiculata) germination (rate of germination, shoot length and fresh weight), except the ethyl palmitate which stimuled the rate of germination and the shoot length of cowpea small plant. None of the identified compounds was toxic on J774 (murine macrophages), WI-38 (human lung fibroblasts), human HeLa(human cervix carcinoma cells) and melanoma Mel-43 cell.La purification de l’extrait éthanolique de la partie aériènne de Justicia anselliana a permis d’obtenir des fractions actives dont l’analyse GC-MS conduit à l’identification de dix composés connus : cinq stérols(campestérol; stigmastérol; acétate de β-sitostérol; 9, 19-cyclolanostan-3-ol, 24-méthylène; 9, 19-cyclolanost-24-èn-3-ol), deux triterpènes (α – amyrine; lupéol), un diterpène (phytol) et deux dérivés d’alcane (hénéicosane; palmitate d’éthyle). Huit de ces composés sont pour la première fois identifiés dans Justicia anselliana. Des composés identifiés ont été testés pour leurs effets allélopathiques sur la germination du niébé (Vigna unguiculata) et pour leurs activités cytotoxiques sur des cellules humaines(HeLa, WI-38 et Mel-43) et de souris (J774). Tous les composés testés ont montré un effet d’inhibition sur les trois paramètres de germination du niébé mesurés (le taux de germination, l’élongation de la plantule et le poids frais de la plantule), à l’exception du palmitate d’éthyle qui stimule le taux de germination et l’élongation de la plantule du niébé. Les composés identifiés et testés ne sont pas toxiques sur les cellules J774 (murine macrophages de souris), WI-38 (fibroblastes embryonnaires humains de poumon), HeLa(cellules cancéreuses humaines du col de l’utérus) et melanoma Mel-43

Social institutional dynamics of seed system reliability: the case of oil palm in Benin

<div><p>Seed system reliability is of major importance in farming. Whereas earlier studies analysed mainly annuals, this study focuses on a perennial. Oil palm in Benin was chosen as a case study because farmers complained about non-hybrids (<i>dura</i> and <i>pisifera</i>) in plots allegedly planted with 100% hybrid (<i>tenera</i>). This study assessed the reliability of the oil palm seedling supply system over past decades and its main drivers. An event ecology approach was used to identify causal mechanisms accounting for the observed variation in oil palm types on smallholder plots. A total of 378 plots belonging to 248 farmers that were allegedly planted with <i>tenera</i> between 1969 and 2009 were sampled, and shell thickness of fruits was assessed to determine whether palms were <i>tenera</i>, <i>pisifera,</i> or <i>dura</i>. The proportion of <i>tenera</i> varied with seedling supply source, farmers' geographic position, seedling purchase price, and year of planting. The proportion of <i>tenera</i> decreased with year of planting. Socio-institutional mechanisms associated with the observed variation in smallholder plots were national policy change, local arrangements for seedling supply to smallholder farmers, and farmers' personal characteristics. The implications of the observed decrease in the reliability of the seedling supply system are discussed.</p></div