Pesticide resistance in Plutella xylostella (Lepidoptera: Plutellidae) populations from Togo and Benin

Published online: 17 August 2016The diamondback moth, Plutella xylostella (L.) is the major insect pest of cabbage crops in Togo and Benin. For control, farmers very often resort to spraying chemical insecticides at high dosages with frequent applications. Bioassays were carried out on three populations of P. xylostella, two from Togo (Kara and Dapaong) and one from Benin (Cotonou), to assess their level of susceptibility to currently used insecticides. A reference strain of P. xylostella from Matuu in Kenya was used as a control. In the laboratory, three insecticide representatives of different chemical families (deltamethrin, chlorpyrifos ethyl and spinosad) were assayed against third instar larvae of P. xylostella. Results revealed that P. xylostella populations from Dapaong, Kara and Cotonou were more resistant to deltamethrin (13 to 59-fold at LC50 level, 149 to 1772-fold at LC90 level) and chlorpyrifos ethyl (5 to 15-fold at LC50 level, 9 to 885-fold at LC90 level) than the reference strain. Spinosad was more toxic to P. xylostella populations than the other insecticides with LC50 and LC90 values less than 1 μg/ml and 15 μg/ml, respectively. However, the population from Cotonou appeared significantly more resistant to spinosad compared to the reference strain. These results are discussed in the light of developing an integrated pest management strategy for reducing the selection pressure of spinosad

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

How does IPM 3.0 look like (and why do we need it in Africa)?

Open Access Article; Published online: 09 Aug 2022The concept of Integrated Pest Management (IPM) was introduced sixty years ago to curb the overuse of agricultural pesticides, whereby its simplest version (IPM 1.0) was aiming at reducing the frequency of applications. Gradually, agro-ecological principles, such as biological control and habitat management, were included in IPM 2.0. However, throughout this time, smallholder farmers did not improve their decision-making skills and continue to use hazardous pesticides as their first control option. We are therefore proposing a new paradigm — IPM 3.0 — anchored on 3 pillars: 1) real-time farmer access to decision-making, 2) pest-management options relying on science-driven and nature-based approaches, and 3) the integration of genomic approaches, biopesticides, and habitat-management practices. We are convinced that this new paradigm based on technological advances, involvement of youth, gender-responsiveness, and climate resilience will be a game changer. However, this can only become effective through redeployment of public funding and stronger policy support

Some biological parameters of Paracoccus marginatus Williams and Granara de Willink (Hemiptera: Pseudococcidae) and its natural enemy Acerophagus papayae Noyes et Schauff (Hymenoptera: Encyrtidae)

The papaya mealybug Paracoccus marginatus Williams and Granara De Willink (Hemiptera: Pseudococcidae) is an invasive insect species attacking diverse host plants causing enormous damage to crops including those of very high economic importance. Biological control of this mealybug is achieved through the field release of its natural enemy, Acerophagus papayae Noyes and Schauff (Hymenoptera: Encyrtidae). The study aims to determine the developmental time and mortality rate of the different stages of P. marginatus; daily fecundity and pre- oviposition, oviposition and post-oviposition times of a female P. marginatus and the total average number of emerging individuals of the hosts parasitized in 24 hours by a female and the total average development time of A. papayae. This study, which was conducted in the laboratory under conditions of 28 ± 2°C, 75 ± 5% RH, 12: 12 LD, determined the average daily fecundity of a female P. marginatus and the average number of offspring of a female A. papayae per day. The results obtained showed that a female P. marginatus has three periods of reproductive activity, namely the pre-oviposition, oviposition and post-oviposition periods, which are on average last 7.74 ± 1.26, 6.13 ± 3.02 and 7.45 ± 4.27 days respectively. During oviposition, a female P. marginatus lays an average of 25.262 ± 11.16 eggs per day, and an average total of 224.32 ± 29.99 eggs during her lifetime, which averages 18.44 ± 3.31 days. Also, during the development of the pre-imaginal stages of P. marginatus, significant mortality rates were noted in the first and second larval stages, which are 61.40 ± 0.05 and 52.8 ± 0.025 respectively, whereas in the third stage, this rate is 35.02 ± 0.03 for the female and zero for the male. The average total development time of the pest was 25.98 ± 4.47 days for the female and 29.70 ± 5.58 days for the male. In contrast, the progeny of its natural enemy A. papayae averaged 8.22 ± 4.676 males and 10.53 ± 4.43 females per day, giving an average total of 18.75 ± 9.087 offspring per day. During its lifetime (13.02 ± 0.08 days), a female A. papayae produced an average of 205.96 ± 9.87 offspring in an average development time of 13.82 ± 0.013 days. These results obtained on the progeny of a female and the development time of A. papayae species in relation to that of its host can be used to evaluate the effectiveness of the parasitoid in the management of the pest populations in Togo

Perception of farmers on seed production constraints of Jatropha curcas L. (Euphorbiaceae)

Asian Research Publishing Network (ARPN)Many countries have understood that an alternative is needed to the problems of depletion of fossil fuels. Emphasis is therefore put on biofuel-producing crops. One of the most important biofuel-producing plants in tropical is Jatropha curcas L. Several biotic and abiotic constraints limit J. curcas production. The present survey was performed in 13 villages in Benin to assess farmers' perceptions on the biotic constraints. These villages were located in J. curcas production supervised by the non-governmental organization ((Renewable Energy Group, Environment and Solidarity)), One hundred and three producers, representing 25% of the 411 producers of the 3 sites were surveyed. Most producers were illiterate. Only 20 to 40% went to school. About 90% of producers indicated that J. curcas is damaged by pests. During the study, the pictures of the main pests reported in the literature were shown to producers. The producers recognized pests in a proportion of 34, 32 and 43% in Cove, Djidja and Zagnanado, respectively. This shows that most of them could not easily identify pests in pictures. These pests are Meloidogyne incognita (Kofoid and White) Chitwood, Phenacoccus manihoti Matile-Ferrero (Homoptera: Pseudococcidae), Aulocophora africana Lucas (Coleoptera:Chrysomelidea), Stomphastis thraustica Meyrick (Lepidoptera: Graciillariidae), Scutellera nobilis Fabricius (Heteroptera:Scutelleridae) and Pempelia morosalis Saalm Uller (Lepidoptera:Pyralidae). No local name was given to these pests, pointing at the lack of knowledge on their status as pests. Their monitoring is therefore necessary as a first step in order to develop sustainable management methods

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

Comparative study of the efficacy of entomopathogenic fungi, chemicals and botanical pesticides in the management of cotton pests and their natural enemies in Benin

In many African countries, the misuse of chemical insecticides is questioned with the awareness of their negative effects on ecosystems and human health. There is, therefore, constant request from consumers for alternatives to chemical insecticide in plant protection. In the present study, the efficacy of Beauveria bassiana, Metarhizium anisopliae, neem oil and pesticides used for conventional cotton was tested in two environments: (i) experimental plots (Research Centre), (ii) farmers’ cotton field). For the purpose, fifty grams per ha of conidia of each fungus’s strains were formulated with peanut oil and kerosene (30:70) and applied at a volume of 2 litres.ha-1. Neem oil was applied at 1 litre.ha-1 in a formulation containing neem oil and kerosene (50:50). Treatments with biopesticides and neem oil were carried out on threshold (five H. armigera for 40 cotton plants). The effects of the different pesticides used on cotton pests populations’ densities (Helicoverpa armigera, Earias spp., Diparopsis watersi, Spodoptera littoralis, Syllepte derogata) and their natural enemies were studied as well as their damage on cotton buds and bolls. Cotton yield was also assessed. The results showed that, in the experimental plots the average efficacy of pesticides used, calculated on the basis of the observations of Helicoverpapopulation’s density was: 56.1 ± 27.4%; 77.9 ± 9.9%; 59 7 ± 18.6% and 78.21 ± 8.2% for chemical pesticides, neem oil, B. bassiana and M. anisopliae, respectively. The average rate of flowers buds and bolls damaged in plots treated with biopesticides was significantly higher than in plots treated with chemicals. M. anisopliae, B. bassiana and neem oil have protected the fruiting organs in the same manner. In farmers’ cotton fields, pest control by the various pesticides used was similar with yields ranging from 1.5 ± 0.3 t / ha to 1.6 ± 0.3 t / ha. Among the natural enemies observed, ants were the most affected by chemical treatments. Among the biopesticides, M. anisopliae represented the least harmful to natural enemies, followed by B. bassiana. The results showed that the biopesticides used in our study can reduce the densities of different target pests. Early application (at lower threshold) allowed these biopesticides to better control cotton pests.This study suggested the possibilities of the use of biopesticides as alternatives to chemical insecticides in the control of cotton pests

Integrated protection of stored products

L'augmentation de la production rizicole en Afrique Subsaharienne et la recrudescence conséquente des ravageurs de stocks tels que Sitophilus oryzae et Sitotroga cerealella nécessitent des actions d'accompagnement de la recherche afin de préserver la qualité et la quantité des récoltes entreposées. Les méthodes de lutte les plus largement utilisées en milieu paysan dans le cadre de la protection des stocks sont les méthodes chimiques. Il apparaît nécessaire de développer de nouvelles mesures de protection des stocks afin de minimiser les risques liés à l'usage des produits chimiques sur la santé des producteurs et celle des consommateurs. L'objectif de cette étude était de développer des technologies alternatives basées sur le traitement des emballages avec les huiles essentielles de Cymbopogon citratus (citronnelle) et d'Eucalyptus camaldulensis afin de protéger efficacement le riz stocké contre ces ravageurs. Pour mener à bien l'étude, deux procédés ont été utilisés: l'imprégnation des sacs en jute et le traitement des sacs en cretonne par pulvérisation. Les sacs en jute ont été trempés dans les huiles essentielles diluées dans l'alcool à des concentrations de 3%, 4% et 5% correspondant respectivement à des doses de 2.34 ml; 3.12 ml et 3.9 ml/sac. Les sacs en cretonne ont été traités soit avec un seul produit (à la dose de 0.25 ml/sac), soit avec les deux huiles associées (à la demi-dose de 0.125 ml/sac). 24 heures après l'application des produits, chaque sac a reçu 100 g de riz paddy, puis a été infesté artificiellement avec 10 couples d'adultes de S. oryzae et de S. cerealella. 90 jours après traitement, les populations des deux espèces ainsi que leurs dégâts ont été évalués. Les résultats ont montré que l'imprégnation des sacs en jute et le traitement des sacs avec les huiles essentielles de C. citratus et d'E. camaldulensis constituent des moyens efficaces de protection du riz stocké contre S. oryzae et S. cerealella. En outre, l'association des deux huiles appliquées sur des sacs en cretonne recouverts d'un sac plastique étanche, est apparue comme la technique la plus efficace pour lutter contre ces ravageurs. Les résultats obtenus avec ces produits naturels sont prometteurs mais avant de vulgariser ces technologies, il est nécessaire d'analyser leur effet sur la qualité des denrées traitées et de s'assurer de leur innocuité vis-à-vis des consommateurs

Economic Losses from Insect Pest Infestation on Rice Stored on-farm in Benin

In Benin, on-farm storage of paddy rice is increasingly exposed to pest damage. Insect infestation causes a loss of income to farmers and other post-harvest stakeholders. The objective of this study is to assess the magnitude of damage caused to rice stored on-farm and evaluate the potential economic risk. In this study, 65 stocks of paddy rice were inspected and sampled in order to assess the economic losses. In addition, an agronomic survey was carried out to determine producer perceptions about the economic impact of stored rice pests in a farming environment. The findings show that weight loss amounts to 5.47% after 6 months of storage in the southern region, 4.07% in the central region and 1.64% in the northern region. From an economic perspective, 6 months duration of storage is likely to cause an estimated loss of 21,315 FCFA (Franc of the African Financial Community) per ton of paddy in the South region, compared to losses of 8,088 FCFA in the North. Furthermore, 36.92% of farmer respondents consider that these insects cause considerable economic damage to stored rice. This study made it possible not only to assess current losses attributable to insect pests in the country but also to obtain future projections about trends in high-risk regions. These findings will undoubtedly pave the way for future research in improved stored rice protection and income safeguards for various stakeholders intervening in the post-harvest sector