Farmers knowledge and control of two major pests: Helicoverpa armigera (Hübner) (Lepidoptera, Noctuidae) and Aphis gossypii (Glover) (Homoptera: Aphididae) in five agroecological zones in Benin (West Africa)

A survey study was performed in five agro-ecological zones in Benin to assess farmers’ knowledge and perceptionon the identification, damage recognition, applied control methods of two cotton insect pests Helicoverpaarmigera Hübner and Aphis gossypii Glover. A total of 200 farmers were interviewed in the five agroecologicalzones in Benin, using semi-structured questionnaire interviews. Results revealed sound knowledge of farmers onthe identity of H. armigera and A. gossypii. Farmers easily recognized H. armigera through its damage ondifferent plant organs while A. gossypii was known only at high infestation stage. Moreover, many crops arelisted as host plants for H. armigera and A. gossypii with different economic injuries. Control of these insectpests was done mainly by the use of chemicals with various application numbers and frequencies. The mostapplied chemicals for the control of H. armigera on cotton were Nurelle D 236 EC in zone 4 and 6, Thunder145O-Teq in zone 5 and Tihan 175 O-Teq in zone 2, while protection against A. gossypii was done using mostly Thian175 O-Teq except in the zone 6 where Fanga was used. The time interval between two treatments was 3-14 daysdepending on the product in use, the target insect and the agro-ecological zone. The effectiveness of the differentproducts was diversely appreciated. Farmers claimed to be aware of the so many side effects of chemicalsapplication. In organic cotton area, alternative method consisting of the use of botanical extracts was beingexperimented

Survey of potential insect vectors of Rice Yellow Mottle Virus in the southern and central rice basin of Benin

Open Access JournalObjectives: Insects are considered as the main vectors of Rice Yellow Mottle Virus (RYMV) in Africa. However, in Benin, little is known about the abundance and diversity of potential insect vectors of RYMV in rice fields to prevent and manage disease impact on rice production. Methodology and Results: The inventory of the potential insect vectors of this disease was carried out in the rice basin of the Southern and Central of Benin where three sites namely AfricaRice station, Koussin and Ouedeme, were prospected. The sweep net technique, visual observation and yellow plates trap were used to conduct the surveys. Eighty insect species belonging to 28 families and 8 orders were recorded at rice tillering, booting, heading and maturation stages. Variation of insect diversity was low among the sites. The shorthorned grasshopper Oxya hyla (Serville), the ladybird beetle Chnootriba similis (Mulsant), the rice white leafhopper Cofana spectra (Distant) and the stalk-eyed fly Diopsis thoracica (Westwood) were the most important species considering their relative abundance (10.62%, 5.19%, 7.99% and 7.01%, respectively) and frequency of occurrence (90%, 80%, 73.33% and 80%, respectively). These insects were mostly present at tillering and booting stages. Conclusion and application of results: Seventy-five (75 %) of the recorded species were not identified as RYMV vectors before. Special attention must be paid to the distribution and importance of these insects in the fields. Studies on their ability to transmit RYMV according ecological conditions should be done to know high-risk production areas and to prevent large epidemics of RYMV

EFFICACY OF VEGETABLE OIL EXTRACTS FOR CONTROL OF INSECT PESTS OF TOMATO IN SOUTHERN BENIN

Pests are a menace to production of tomato ( Lycopersicon esculentum Mill.) in sub-Sahara Africa. The objective of this study was to evaluate the efficacy of oil extracts of selected common plants for control of pests of tomato in Benin. The study was carried out on the Togba market garden sites in Benin. The botanical pesticides ( Tephrosia purpurea , Ricinus communis , Thevetia neriifolia and Cashew Nut Shell Cold Liquid (CNSL cold) were compared with a biological insecticide (Topbio), a synthetic insecticide (Lambda cyhalothrin) and an untreated negative control. The fish model and the generalised linear mixed or fixed effects model were used to explain the number of caterpillars per plot as a function of the products tested during the different plant phases. Tephrosia purpurea oil, cold CNSL, Topbio and lambda cyhalothrin treatments significantly reduced H. armigera, S. littoralis and T. absoluta populations. The average yields of marketable tomato ranged from 7.20 \ub1 0.89 t ha-1 for the controls and 21.14 \ub1 3.56 and 20.46\ub11.98 t ha-1 for the plots treated with Tephrosia purpurea and CNSL cold on tomato, respectively. Plots treated with the synthetic insecticide lambda cyhalothrin gave the best yields (31.15\ub13.20 t ha-1). Of all the extracts tested, cold extracted CNSL and T. purpurea oil showed very high larvicidal activity at doses of 10%, compared to R. communis and T. neriifolia oil on the farm. The larvicidal activity of the extracts observed at low doses on H. armigera and S. littoralis larvae seems to offer an alternative advantage for the control of tomato pests.Les ravageurs sont une menace pour la production de tomate (Lycopersicon esculentum Mill.) en Afrique sub-saharienne. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer l\u2019efficacit\ue9 des extraits d\u2019huile de Tephrosia purpurea, Ricinus communis, Thevetia neriifolia et Cashew Nut Shell Cold Liquid (CNSL cold) pour le contr\uf4le des ravageurs de la tomate. L\u2019\ue9tude a \ue9t\ue9 r\ue9alis\ue9e sur les sites mara\ueechers de Togba au B\ue9nin. Les pesticides botaniques ont \ue9t\ue9 compar\ue9s \ue0 un insecticide biologique (Topbio), un insecticide de synth\ue8se (Lambda cyhalothrine) et un t\ue9moin n\ue9gatif non trait\ue9. Le mod\ue8le poisson z\ue8bre et le mod\ue8le lin\ue9aire g\ue9n\ue9ralis\ue9 \ue0 effets mixtes ou fixes ont \ue9t\ue9 utilis\ue9s pour expliquer le nombre de chenilles par parcelle \ue9l\ue9mentaire en fonction des produits test\ue9s lors des diff\ue9rentes phases de la plante. Les traitements \ue0 l\u2019huile de Tephrosia purpurea, au CNSL cold, au Topbio et \ue0 la lambda cyhalothrine ont significativement r\ue9duit les populations de H. armigera, S. littoralis et T. absoluta. 20,46\ub11,98 t ha-1 pour les parcelles trait\ue9es respectivement avec Tephrosia purpurea et CNSL cold sur tomate. Les parcelles trait\ue9es avec l\u2019insecticide de synth\ue8se lambda cyhalothrine ont donn\ue9 les meilleurs rendements (31,15\ub13,20 t ha-1). De tous les extraits test\ue9s, l\u2019huile de CNSL cold et de T. Purpurea extraite a montr\ue9 une activit\ue9 larvicide tr\ue8s \ue9lev\ue9e \ue0 des doses de 10% par rapport \ue0 l\u2019huile de R. communis et de T. neriifolia \ue0 la ferme. L\u2019activit\ue9 larvicide des extraits observ\ue9e \ue0 faible dose sur les larves de H. armigera et S. littoralis semble offrir un avantage alternatif pour la lutte contre les ravageurs de la tomate

Sensitivity of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidea) to the Entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana in laboratory.

The present work aims to assess the pathogenicity of the conidia of six isolates of Metarhizium anisopliae and two isolates of Beauveria bassiana on Helicoverpa armigera in order to select the most promising ones for developing a microbiological product to be used in cotton fields. The pathogenicity of six isolates of the entomopathogenic fungi, M. anisopliae (Met 28, Met 32, Met 92, Met 31, Met 34 and Met 341) and two isolates of B. bassiana (Bb11 and Bb 12) was evaluated in the laboratory by applying topically 1 μl of an oil-based formulation of conidia at a concentration of 108 conidia/ml on the third, fourth, fifth and the sixth instars of H. armigera. Taken separately, each isolate caused less mortality among the larvae of the sixth stage than in younger stages. Corrected mortality rates varied from 3.6 ± 1.8 % (Met 28, sixth instar) to 56.3 ± 0.8% (Met 31, third instar) for M. anisopliae and from 3.6 ± 1.8 % (Bb 12, sixth instar) to 34.4 ± 4.2% (Bb 11, third instar) for B. bassiana. Certain isolates of Metarhizium were infective to pupa. Host development stage at inoculation affected both survival times compared to control. The results of the presented study showed that the isolates of Metarhizium (Met 31) and Beauveria (Bb 11, known as Bba 5653), the last being tested successfully against Plutella xylostella (Lepidoptera: Noctuidae), are virulent isolates and can be promising isolates for the control of the cotton bollworm H. armigera

Pratiques paysannes et utilisation potentielle de Metarhizium flavoviride Gams and Rozsypal en lutte antiacridienne au Niger

A socio-economic study was executed in South East Niger to determine the conditions under which a novel mycopesticide based on the fungus Metarhizium flavoviride could be introduced for locust and grasshopper control as a possible alternative reducing the use of synthetic chemicals. From the interviews, all farmers estimated locusts and grasshoppers to be one of three major pests. The survey revealed that 93.8% of the farmers conduct collective pesticide applications. About 45.5% of the farmers received support from the brigades, at least once. The remaining farmers (54.5%) were not assisted by the brigades due to a lack of pesticides. Farmers estimate that the choice of any pesticide greatly depends upon its knock-down ability (57.5%) or the numbers of cadavers found after a treatment (42.5%). Most farmers (82%) consider the government to be responsible for locust and migrant grasshoppers control. On average, farmers were willing to pay US$ 1.00 per ha per year, to protect their crops

Use of Metarhizium flavoviride for control of Zonocerus variegatus: a model, relating mortality in caged field samples with disease development in the field

A field trial was conducted using an oil formulation of the entomopathogenic fungus, Metarhizium flavoviride Gams & Rozyspal (Deuteromycotina: Hyphomycetes), to control the variegated grasshopper, Zonocerus variegatus L. (Orthoptera: Pyrgomorphidae). The influence of dispersal and secondary pick‐up from the spray residue on mortality was assessed by sampling insects from the treated plots at intervals and monitoring disease levels during subsequent incubation in the laboratory. The cumulative mortality curves showed the pathogen to be highly effective, even in samples taken 8 days after spraying. A model was developed to link the influence of mortality, incubation, secondary pick‐up of spores and insect dispersal, on the shape of these cumulative mortality curves. The model proved useful for data received from an experiment using small plot sizes, where insect dispersal is a big problem. The spray residue had an important influence on overall insect mortality. The model also indicated a difference in speed of kill between field and laboratory samples, suggesting an incubation delay in the fiel

Cycle biologique duree des stades larvaires du criquet puant, Zonocerus variegatus (Linne, 1758) (Orthoptera: Pyrgomorphidae) au sud du Benin

The life cycle and development of Zonocerus variegatus (variegated grasshopper) from southern Benin was studied at the International Institute of Tropical Agriculture (IITA) Benin Station, from March 1992 to August 1994. Hoppers of the 1st to the 5th stage were collected from uncultivated fields in the Atlantic Province and placed in cages and their development evaluated by counting the number of insects in each stage every two days until the adult stage. Mating and the number of egg pods were also recorded. The study showed that Z. variegatus has only one generation in southern Benin, running from September/October to July/August. Hatching occurs between September/ October and February/March. Zonocerus variegatus females can oviposit up to five times and the interval between ovipositions varies from 14 to 32 days. The variegated grasshopper has an egg diapause and egg hatching is not synchronised. These observations explain the almost perennial presence of the variegated grasshopper in southern Benin

Effects of moisture content and temperature on storage of Metarhizium flavoride conidia

The effects of moisture content and temperature on the medium-term (3-4 months) storage of conidia of Metarhizium flavoviride were investigated. Conidia harvested after 24 days of culturing on rice showed greater tolerance to long storage than conidia from 12-day cultures. The moistut-e content of the conidia was of greatest importance; at harvest from the culture. conidial moisture contents could be > 40%, while the optimal moisture content for storage was found to be 4-5%. Dried conidia stored in oil benefited from the addition of dried silica gel, as did conidia stored as powder. A range of mineral oils proved satisfactory for storage, and when dried silica gel was added to suspensions, germination levels were 79.8% after 105 days at 28-32°C. Dried conidia stored in oil maintained germination levels of up to 96 and 85% after 80 days at IO-14°C and 28-.UoC respectively. Dried conidia stored as powder retained germination levels of 95% at JO-I4°C. but only up to 27% at 28-32°C. In another experiment, dried conidia maintained greater than 90% germination over 128 days, with or without silica gel at JO-14°C or 15- 18°C

Reponse des stades larvaires de Helicoverpa armigera (Hubner) (Lepidoptera : Noctuidae) a lapplication de champignons entomopathogenes Metarhizium anisopliae et Beauveria bassiana

Abstracts also in English LanguageDeux expérimentations ont été mises en place pour étudier la réponse effet/dose de deux souches de champignons entomopathogènes, Metarhizium anisopliae, Met 31 et Beauveria bassiana, Bb 11 sur les stades larvaires de Helicoverpa armigera. Dans la première expérimentation, la souche Met 31 de M. anisopliae a été testée sur le stade L3 de H. armigera, tandis qu’à la deuxième, les deux souches Met 31 et Bb 11 ont été testées sur le stade L4 du même insecte. Pour les deux expérimentations, les doses de 0, 104, 105, 106, 107 conidies par insecte ont été utilisées. Les observations ont porté sur la mortalité des larves, la sporulation des cadavres, la formation des chrysalides et l’émergence des adultes. La formule d’Abbott a été utilisée pour corriger les taux de mortalité au niveau des insectes traités. La régression de Cox a été utilisée pour déterminer la DL50. Pour la première expérimentation, les taux de mortalité des larves L3 de H. armigera n’étaient pas significativement différents entre les doses d’application de Met 31 de 106 et 107 conidies par insecte. Lors de la deuxième expérimentation, le taux de mortalité des larves L4 (74 %) soumises à la dose d’application de Met 31 de 107 conidies par insecte a été significativement le plus élevé. Pour la souche Bb 11, malgré l’écart observé entre les taux de mortalité causés par 106 (58 %) et ceux causés par 107 conidies par insecte (90 %), aucune différence significative n’a été enregistrée au seuil de 5 %. Les cadavres des chenilles L4 issus des plus faibles doses n’ont pas sporulé. Les témoins ont enregistré le plus fort taux de chrysalides et d’adultes. Ces deux paramètres ont été fonction de la dose : plus la dose est forte, moins élevés sont les taux de chrysalides et d’adultes. Pour toutes les souches de champignons utilisées, quel que soit le stade larvaire de H. armigera, la réponse effet/dose a été significative