Réponse des stades larvaires de Helicoverpa armigera (Hübner) (Lepidoptera : Noctuidae) à l'application de champignons entomopathogènes Metarhizium anisopliae et Beauveria bassiana

Response of the nymphs of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) to entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana. Two experiments on dose/mortality response between the instars of Helicoverpa armigera and two strains of entomopathogenic fungi, Metarhizium anisopliae (Met 31) and Beauveria bassiana (Bb 11) were carried out in laboratory conditions. In the first experiment, M. anisopliae Met 31 was tested on the third instar of H. armigera, while in the second experiment, both Met 31 and Bb 11 were tested on the fourth instar. In all the experiments, the following different doses of conidia per insect were used: 104, 105, 106, 107. The following parameters were measured: mortality and sporulation rates, the number of pupae formed and the number of adults that emerged. Abbott's formula was used to correct the treatment mortality rates. LD50 was determined using Cox-regression. For the third instar in experiment one, no significant difference was observed between high doses (106 and 107 conidia per insect). For instar L4, only the dose of 107 conidia per insect showed high mortality rates (74%). For the strain Bb 11, in spite of the variation observed between the mortality rates induced by high doses (106 and 107 conidia per insect), no significant difference was recorded at the 5% level. No mycosis was observed from cadavers resulting from lower doses when tested on L4. The control recorded the highest numbers of pupae and adults. These two parameters were related to the level of dosage: the higher the dose, the lower the numbers of pupae and adults that emerged. For all the strains of fungi used, whatever the larval stage of H. armigera, the dose/mortality response was significant

Efficacité d’extraits de feuilles de neem Azadirachta indica (Sapindale) sur Plutella xylostella (Lepidoptera : Plutellidae), Hellula undalis (Lepidoptera : Pyralidae) et Lipaphis erysimi (Hemiptera : Aphididae) du chou Brassica oleracea (Brassicaceae) da

Cette étude vise à évaluer l’efficacité d’extrait hydroéthanolique de feuilles de Azadirachta indica dans la lutte contre Plutella xylostella, Hellula undalis et Lipaphis erysimi, insectes ravageurs du chou dans une approche champ école paysan en milieu maraîcher au sud du Togo. L’efficacité de l’extrait hydroéthanolique a été comparée à celle d’un insecticide de synthèse (Cydim Super) et à celles d’un extrait aqueux de feuilles de A. indica et de deux pratiques paysannes. Les parcelles de chou ont été disposées en blocs complets randomisés et équilibrés. Les traitements à base d’extraits de feuilles de A. indica ont significativement réduit les populations de P. xylostella et de H. undalis par rapport à l’insecticide de synthèse et une pratique paysanne. Par contre, l’insecticide de synthèse a mieux contrôlé L. erysimi. Les rendements moyens en pommes de chou commercialisables sont compris entre 4,68 ± 1,63 t/ha pour le témoin, et 17,38 ± 0,98 t/ha pour les parcelles traitées avec l’extrait hydroéthanolique. Cet extrait a donné le double ou le triple du rendement des autres traitements. L’extrait hydroéthanolique peut être utilisé dans la gestion intégrée de P. xylostella, H. undalis et de L. erysimi sur le chou.Mots clés : Azadirachta indica, insectes ravageurs, chou, Togo

Comparaison de quelques caractéristiques biologiques entre Dinarmus basalis Rond. (Hymenoptera: Pteromalidae) élevé soit sur son hôte habituel Callosobruchus maculatus F. (Coleoptera: Bruchidae) soit sur Acanthoscelides macrophthalmus Schaef. ou Bruchidius lineatopygus Pic. identifiés comme hôtes de substitution

Comparison of some Biological Characteristics between Dinarmus basalis Rond. (Hymenoptera: Pteromalidae) Reared either on his Habitual Host Callosobruchus maculatus F. (Coleoptera: Bruchidae) or on Acanthoscelides macrophthalmus Schaef. and Bruchidius lineatopygus Pic. Identified as Substitution Hosts. In this study, we have measured some biological parameters of Dinarmus basalis Rond. (Hymenoptera: Pteromalidae) when this parasitoid grows on three hosts: Callosobruchus maculatus F. (usual host), Acanthoscelides macrophthalma Schaef. and Bruchidius lineatopygus Pic. (substitution hosts). The results of this comparative study in no choice situation show that, life duration and development duration of this parasitoid are identical in laboratory conditions. By contrast, the female fecundity, the sexual rate and the parasitism rate of D. basalis are different according to the hosts presented. Although such differences appear to be small between C. maculatus and A. macrophthalmus. In presence of these two species, the number of eggs laid by the female of D. basalis is respectively 61 ± 5.24 and 54 ± 5.60, the sexual rate 37.63 ± 2.13% and 41.73 ± 3.69% and the parasitism rate 85.46 ± 2.61% and 76.48 ± 5.90%. This indicates that these two Bruchids can be used as hosts to D. basalis for a mass production. In presence of B. lineatopygus, the fecundity and the parasitism rate of D. basalis female are very low and the sexual rate more favourable of the males. This situation is unfavourable for a parasitoid production. When D. basalis females are placed in choice situation with equal number of the hosts nowely C. maculatus and A. macrophthalmus, the parasitism rate obtained, is higher for C. maculatus that of A. macrophthalmus. This parasitism rate remains high for C. maculatus even when the other host A. macrophthalmus is twice the number of C. maculatus. Thus the parasitoid seems to have a preference for his natural host. However, A. macrophthalmus can still be used in production unit of D. basalis

Larvicidal activities of Biostop Moustiques®, a botanical insecticide on field collected malaria mosquito Anopheles gambiae sensu lato in Togo

The larvicidal activity of a botanical insecticide, Biostop Moustiques® (BM), was studied on field collected larvae of Anopheles gambiae s.l at the  concentrations of 1, 5, 10 and 20 mL/L of water. The samples were made based on three different localities of Togo: Lomé, Kovié and Kolokopé. BM had high mortality rates at 20 mL/L in all instars larvae. Specifically,  significant high mortality rates were recorded in L3 and L4 from field collected strain at a very low concentration (1 mL/L), compared to laboratory strain. In general, this study showed that the botanical insecticide tested has almost the same larvicidal effect no matter the strains of Anopheles gambiae used.Keywords: Biostop Moustiques®, Larvicidal activity, Anopheles gambiae, Togo

Susceptibility to DDT and pyrethroids, and detection of knockdown resistance mutation in Anopheles gambiae sensu lato in Southern Togo

Insecticides play an important role in malaria control programmes especially in Sub-Saharan Africa. However, the development of resistance by vectors to most commonly used public health insecticides has become a very crucial problem. DDT (Dichlorodiphenyltrichloroethane) was used worldwide to control malaria vectors and pyrethroids have been used in many vector control projects due to their known efficiency and lower toxicity to humans and non-target organisms. In West Africa, resistance to pyrethroid in the major malaria vector, Anopheles gambiae, had been reported in several countries. The last publication on this phenomenon in Togo was done in Togo in 2005. An update on the susceptibility of the malaria vector and characterization of its resistance mechanism becomes therefore crucial. Newly emerged female mosquitoes of two to five days old were selected and exposed to DDT 4%, Permethrin 1% and Deltamethrin 0.05%, the WHO diagnostic doses. These adult mosquitoes were from larvae of Anopheles gambiae sensu lato collected from rural and urban settings and reared in an insectary. A susceptible laboratory strain of An. gambiae sensu stricto was used as reference. Species identification was made using the morphological characteristics, PCR (polymerase chain reaction), and HhaI (Haemophilus haemoliticus) restriction digest. Knockdown resistance mutation screening was conducted on both living and dead mosquitoes. An. gambiae sensu stricto was the only sibling species of the complex present in Kovié and Lomé. The molecular M form was predominant in the two localities (almost 100%). High resistance level was observed in Lomé 1.19%, 56.45% and 41.17%; and in Kovié 0.91%, 55.55% and 67% mortality respectively to DDT 4%, Deltamethrin 0.05% and Permethrin 1% with a very high knockdown time (TKD50). Up to 70% of resistant individuals have been obtained in the two localities. It is important to inspect these localities through routine tests in order to decide on possible alternative strategies to be used. This study showed that An. gambiae is highly resistant to both DDT and pyrethroids in Lomé and Kovié, with the presence of kdr allele.Keyword: Anopheles gambiae s.s, DDT, pyrethroids, kdr, Southern Tog

Vegetable production in Togo and potential impact of pesticide use practices on the environment

In West Africa, market gardening is considered one of the sectors in agriculture that consumes lots of pesticides. In order to study (i) the principal protection practices of vegetables and (ii) the inherent environmental risks to pesticide use practices, a survey was carried in Togo from 2010 to 2011. A random selection of 161 farmers were interviewed on their farms, which are distributed over the most important vegetable production sites located in dry Savanna, forests and littoral zones of Togo. The results showed that 88% of farmers interviewed responded that, insects are the most important vegetable pests in Togo. Crop protection  practices are primarily based on excessive use of synthetic pesticides which in most cases include organophosphates (27.3%) and pyrethroids (18.2%), known to be dangerous to human health and environment. Despite the excessive use of pesticides, farmers revealed that insect pests continue to cause serious damages, which is an indication that they have developed a resistance to pesticides. Moreover, about 80% of farmers did not have adequate materials for handling and  application of pesticides and are thus exposed to pesticide poisoning. An integrated pest management programme based on crop rotation, biological control and biopesticides is discussed.Keywords: Farmers, market gardening, crop protection, pests’ resistance

Analyse de quelques aspects du système de production légumière et perception des producteurs de l’utilisation d’extraits botaniques dans la gestion des insectes ravageurs des cultures maraîchères au Sud du Togo

L’une des contraintes liée à la production maraîchère, est la pression exercée par les insectes ravageurs. Cette étude analyse quelques aspects du système de production légumière ainsi que la perception des   producteurs de l’utilisation d’extraits botaniques dans la gestion des  insectes ravageurs des cultures maraîchères. Elle a été réalisée à travers une enquête menée auprès de 217 maraîchers au Sud du Togo. L’analyse descriptive des données a révélé que plus d’hommes (72%) que de femmes (28%) pratiquent le maraîchage. Seul 33% a suivi une fois une formation en maraîchage. La contrainte majeure dans la production maraîchère est le problème de ravageurs et de maladies dont les principaux sont des insectes, des nématodes et des champignons. La lutte chimique constitue la principale méthode de lutte contre ces ravageurs. Néanmoins, les maraîchers connaissent des dangers induits par l’utilisation des pesticides de synthèse et sont au courant de l’utilisation des pesticides botaniques en maraîchage. Cependant, très peu les utilisent dans la gestion des ravageurs. Mais, ils sont disposés à utiliser les pesticides botaniques si ceux-ci sont disponibles, accessibles, efficaces et pas trop chers pour pallier les effets néfastes des pesticides de synthèse à la santé et à l’environnement.Mots clés : Maraîchage, perception des producteurs, extraits botaniques, Sud du Togo

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

Reproductive Capacities and Development of a Seed Bruchid Beetle, Acanthoscelides macrophthalmus, a Potential Host for the Mass Rearing of the Parasitoid, Dinarmus basalis

The reproductive capacities and development of the seed beetle Acanthoscelides macrophthalmus (Schaeffer) (Coleoptera: Bruchidae), found in Togo, were determined under natural conditions in a Guinean zone for its use as a substitute host for the mass rearing of the parasitoid Dinarmus basalts Rond (Hymenoptera: Pteromalidae), a biological agent for the control of beetles that are pests of cowpea, Vigna unguiculata (L.) Walpers (Fabales: Fabaceae). Population dynamics at the field level; and survival, fecundity and offspring production by A. macrophthalmus under laboratory conditions were measured when fed on its natural plant-host Leucaena leucocephala (Lamark) deWit (Fabales: Mimosaceae). The data resulting from the laboratory study were used to calculate the demographic parameters of A. macrophthalmus by establishing its fertility and life tables. Contrary to cultivated leguminous food plants, L. leucocephala is a perennial sub-spontaneous leguminous plant whose pods are available year round. Although A. macrophthalmus was present in nature throughout the year, its infestation rate of the pods fluctuated according to the phenology of the plant. The maximum infestation of L. leucocephala pods was observed between August and December. Four larval stages and one pupal stage of A. macrophthalmus were identified in the laboratory. The total mean development time varied on average 33.75 ± 2.87 days on the mature pods and 33.39 ± 2.02 days on seeds. The adult female lived from one to two weeks. During its life time, the female laid an average of 62.3 ± 19 and 43.1 ± 13 eggs on the mature pods and seeds respectively and produced an average of 36.7 ± 11.3 offspring on the mature pods and 21.8 ± 8.4 offspring on seeds. On seeds, the net reproduction rate was 5.88 females per female and the intrinsic rate of population increase 0.051 per day. The generation time was 34.59 days and the doubling time 13.59 days. The demographic parameters of A. macrophthalmus in this study are close to those of Callobruchus maculatus F. (Bruchidae), the natural host of D. basalts in a previous study. A. macrophthalmus could therefore be used as substitute host for the mass rearing of D. basalts and subsequently its release in farmers' storage containers. The data presented in this study provide some baseline information regarding the reproductive capacities of A. macrophthalmus that may be useful for its promotion as a substitute host for mass rearing of D. basalts

Diversité spécifique des termites (Isoptera) dans deux plantations de tecks (Tectona grandis L.) au sud du Togo

Les termites constituent en Afrique lfune des composantes la plus importante de la macrofaune terricole. Malgre lfimpact benefique sur lfagriculture, au plan de la fertilisation, de lfaeration et de la porositedes sols, certains de ces termites constituent pour la plupart des paysans en Afrique sub-saharienne, un probleme important a cause des degats occasionnes aux cultures et aux plantations dans les agro-systemes ainsique dans les stocks. La connaissance de leur diversite specifique et de leur repartition dans les ecosystemes est un prealable pour entreprendre une lutte adequate contre ces insectes. Cfest dans cet objectif qufun inventaire systematique des termites et une etude de leur repartition ont ete realises dans deux plantations de tecks a Noepe et a Eto, deux localites au sud du Togo. Des fouilles systematiques dans les deux plantations et dans les placeaux le long de transects, ainsi que sur les tecks nous ont permis dfinventorier onze especes de termites. Il sfagit de : Coptotermes intermedius Silvestri, Amitermes evuncifer Silvestri, Ancistrotermes guineensis Silvestri, Microcerotermes sp., Macrotermes bellicosus Smeathman, Microtermes sp., Odontotermes pauperans Silvestri, Pseudacanthotermes militaris Hagen, P. spiniger, Trinervitermes geminatus Wasmann et T. oeconomus. A part ces deux dernieres especes qui ne se retrouvent pas sur les pieds de tecks, toutes les autres especes se rencontrent a la fois dans le sol et sur les pieds de tecks et elles constituent des ravageurs potentiels pour ces essences vegetales, compte tenu de leur regime alimentaire lignivore ou champignonniste. Lfanalyse comparative des deux plantations par le calcul des indices ƒ¿ et ƒÀ a montre que les populations de termites de la plantation dfEto est plus diversifiee que celle de Noepe