Efficacité des pièges à paraphéromone dans la protection des vergers de manguiers greffés contre les mouches des fruits au Togo

Les mouches de fruits en infestant les mangues greffées causent des pertes considérables et un manque à gagner aux différents  acteurs en passant par les producteurs jusqu’aux consommateurs. Pour venir à bout de ces insectes nuisibles, la pulvérisation des insecticides chimiques de synthèse est généralement la solution la plus commune et de premier recours dans toutes les régions du Togo. Mais cette méthode reste dangereuse pour la santé humaine et environnementale et peu rentable économiquement. Cette étude a pour objective de tester l’efficacité du piège Biofeed, une solution alternative, respectueuse de l’environnement et de la santé de l’Homme. Trois vergers d’environ 1 ha pour les trois traitements (piège Biofeed, piège M3 et le control) ont été choisis dans chacune des cinq régions du Togo. Les pièges ont été installés à la prématuration des fruits à une densité de 25 pièges/ha et sont suivis toutes les deux semaines jusqu’à la récolte finale en procédant aux échantillonnages des mangues pour l’évaluation du taux infestation et identification des espèces de mouche de fruits. Après la pose et le suivi des infestations, les pièges Biofeed se sont révélés efficaces en réduisant sur le plan national les dégâts des mouches de fruits de 73,60% tandis que les pièges M3 n’ont entrainé qu’une réductionde 39,94%. Les vergers ayant bénéficiés de ces pièges ont connu des taux d’infestations faibles promettant une bonne récolte. L’incubation des mangues récoltées dans les vergers ont permis de recenser 4 genres de mouches de fruits (Bactrocera, Ceratitis, Dacus, Zeugodacus) et Bactrocera dorsalis est l’espèce la plus abondante retrouvée sur ce fruit d’importance économique. Mots clés : Mouches de fruit, mangue greffée, piège Biofeed, piège M3.   English  title: Efficacy of parapheromone traps in the protection of grafted mango orchards against fruit flies in TogoFruit flies by infesting grafted mangoes cause considerable losses and loss of profit to the various actors range from producers to consumers. To control these pests, synthetic chemical insecticides use is generally the most common and first resort solution in all regions of Togo. But this method remains dangerous for human and environmental health. The objective of this study was to test the effecacy of Biofeed trap, an alternative solution that is environmentally friendly in comparison with a trap already used in the field (M3 traps based on food bait). Three orchards of about 1 ha for the 3 treatments (Biofeed trap, M3 trap and control) were chosen in each of the five regions of Togo. The traps were installed at the premature fruit maturity at a density of 25 traps / ha and were monitored every two weeks until the final harvest by sampling the mangoes for the assessment of the infestation rate and identification of fruits fly species. After setting traps and monitoring the infestations, Biofeed traps proved effective by reducing fruit fly damage by 73.60% nationally, while M3 traps by 39.94%. The orchards that benefited from these traps had low infestation rates that promissing a good harvest. Incubation of the mangoes harvested in the orchards have allowed to identify 4 genera of fruit flies (Bactrocera, Ceratitis,Dacus, Zeugodacus) and Bactrocera dorsalis is the most abundant species found on this economically important fruit.Keywords: Fruit flies, grafted mango, Biofeed and M3 traps

Biological reinforcement learning simulation for natural enemy -host behavior: Exploring deep learning algorithms for population dynamics

This study introduces a simulation of biological reinforcement learning to explore the behavior of natural enemies in the presence of host pests, aiming to analyze the population dynamics between natural enemies and insect pests within an ecological context. The simulation leverages on Q-learning, a reinforcement learning algorithm, to model the decision-making processes of both parasitoids/predators and pests, thereby assessing the impact of varying parasitism and predation rates on pest population growth. Simulation parameters, such as episode count, duration in months, steps, learning rate, and discount factor, were set arbitrarily. Environmental and reward matrices, representing climatic conditions, crop availability, and the rewards for different actions, were established for each month. Initial Q-tables for parasitoids/predators and pests, along with population arrays, were used to track population dynamics. • The simulation, illustrated through the Aphid-Ladybird beetle interaction case study over multiple episodes, includes a sensitivity analysis to evaluate the effects of different predation rates. • Findings reveal detailed population dynamics, phase relationships between predator and pest populations, and the significant influence of predation rates. • These insights contribute to a deeper understanding of ecological systems and inform potential pest management strategies

Effet de quatre souches de champignons mychoriziens arbusculaires sur Meloidogyne spp., principal nématode parasitaire du soja (Glycine max, L.) au Togo.

Objectif : L’objectif de cette étude est d’évaluer l’effet de quatre souches de champignon mycorhizien arbusculaire d’origine locale sur la production du soja et le contrôle des nématodes parasitaires, Meloidogyne sp. au champ.Méthodologie et résultats : L’essai a été conduit à la Station d’Expérimentation Agronomique de Lomé au Togo, de Juillet à Octobre 2016 suivant un dispositif de Fisher à quatre répétitions. Glomus mosseae, Glomus hoï, Acaulospora spinoza et BEN 10 ont été testées en comparaison au témoin. L’inoculation a été faite lors du semis du soja. Il ressort de cette étude que les plants de soja inoculés sont fortement mycorhizés. Sur les quatre souches dans cette étude, Glomus mosseae a induit la meilleure réduction de la densité des nématodes dans les racines, entrainant une amélioration du rendement en graines du soja.Conclusion et applications des résultats : Cette étude a montré que l’inoculation directe des CMA pendant le semis entraine une réduction de la densité des nématodes parasites et améliore le rendement du soja. Elle peut donc être un des moyens écologiquement durable de production du soja au Togo.Mots clés : Inoculation mycorhizienne, nématodes, rendement, soja

Do the invasive Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), and the maize lepidopteran stemborers compete when sharing the same food?

International audiencen insect communities, the outcome of intra- and inter-specific competitions for food utilisation depend primarily upon density and duration even inter-specific competitions can occur when they are not sharing the same feeding niche such as between foliar feeders and stemborers. Experimental manipulations of larval densities and the durations of common diet feeding of fall armyworm (FAW), S. frugiperda, and the African lepidopteran stemborers, Busseola fusca, Sesamia calamistis and Chilo partellus, were conducted to determine how the density and the duration of resource utilization affected larval survival and the relative growth rate (RGR) in intra- and inter-specific interactions. The results showed both intra- and interspecific competitions were observed among all the four species and interspecific competition was significantly stronger between the stemborers than between the FAW and the stemborers. The results showed that multiple infestations of cereal plants with low larval densities of each species at optimum conditions will very likely prolong the coexistence between FAW and stemborers. In addition, the time partitioning of the resource use significantly influenced this coexistence

Cannibalism and intraguild predation involved in the intra- and inter-specific interactions of the invasive fall armyworm, Spodoptera frugiperda, and lepidopteran maize stemborers

Cannibalism and intraguild predation can play important roles in determining spread and survival or death of organisms which share the same resource. However, the relationship between cannibalism and intraguild predation, and the costs and benefits of such behaviours, is difficult to establish within insect communities, and little is known about how such behaviours are affected by invasive species. The present study was aimed at assessing the interactions between larvae of fall armyworm (Spodoptera frugiperda) and maize stemborers (native to Africa, Busseola fusca, and Sesamia calamistis and native to India, Chilo partellus) in relation to cannibalism and intraguild predation when they utilize the same resource. Experiments involving treatments with either single species of S. frugiperda or any of the stemborers or pairwise species combinations with S. frugiperda were conducted under laboratory conditions. The experimental insect larvae were reared on maize leaves and monitored until the last developmental stage where cannibalism and/or intraguild predation, larval survival, and relative growth rate were recorded. Results of the intraspecific interaction indicated that S. frugiperda exhibited cannibalism to a larger degree than the stemborers species, especially at the late instars. The higher cannibalism trait in S. frugiperda turned, however, to competitive advantage as it led to a higher degree of intraguild predation when they cohabit with stemborer species and allowed FAW to gain a greater relative growth rate. Overall, interactions with FAW are detrimental for stemborer species and may be an important factor to explain the invasive success of S. frugiperda. Such knowledge is essential to understand the mechanisms behind ecological interactions between pests with overlapping niches in the field and in designing successful integrated pest management strategies

Influence of Temperature on the Interaction for Resource Utilization between Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), and a Community of Lepidopteran Maize Stemborers Larvae

Intra-and interspecific interactions within communities of species that utilize the same resources are characterized by competition or facilitation. The noctuid stemborers, Busseola fusca and Sesamia calamistis, and the crambid stemborer, Chilo partellus were the most important pests of maize in sub-Saharan Africa before the recent "invasion" of fall armyworm (FAW), Spodoptera frugiperda, which currently seriously limits maize yields in Africa. This new pest is interacting with the stemborer community at the larval stage in the use of maize resources. From previous works on the influence of temperature on the larval intra-and interspecific resources utilization within the community of Lepidoptera stemborers involving B. fusca, S. calamistis, and C. partellus, there is a need to update these studies by adding the new pest, S. frugiperda, in order to understand the effect of temperature on the larval interactions of all these four species under the context of climate change. The influence of temperature on intra-and interspecific larval interactions was studied using artificial stems kept at different constant temperatures (15 • C, 20 • C, 25 • C, and 30 • C) in an incubator and assessing survival and relative growth rates of each species in single and multi-species experiments. After the inclusion of FAW into the experiments, with regard to relative growth rates, both intra-and interspecific competition was observed among all four species. With regard to survival rates, cannibalism can also explain the intra-and interspecific interactions observed among all four species. Interspecific competition was stronger between the stemborers than between the FAW and the stemborers. Similar to lepidopteran stemborers, temperature affected both survival and relative growth rates of the FAW as well. Regardless of the temperature, C. partellus was superior in interspecific interactions shown by higher relative growth and survival rates. The results suggest that the FAW will co-exist with stemborer species along entire temperature gradient, though competition and/or cannibalism with them is weak. In addition, temperature increases caused by climate change is likely to confer an advantage to C. partellus over the fall armyworm and the other noctuids

Influence of Temperature on the Interaction for Resource Utilization between Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), and a Community of Lepidopteran Maize Stemborers Larvae

Intra- and interspecific interactions within communities of species that utilize the same resources are characterized by competition or facilitation. The noctuid stemborers, Busseola fusca and Sesamia calamistis, and the crambid stemborer, Chilo partellus were the most important pests of maize in sub-Saharan Africa before the recent “invasion” of fall armyworm (FAW), Spodoptera frugiperda, which currently seriously limits maize yields in Africa. This new pest is interacting with the stemborer community at the larval stage in the use of maize resources. From previous works on the influence of temperature on the larval intra- and interspecific resources utilization within the community of Lepidoptera stemborers involving B. fusca, S. calamistis, and C. partellus, there is a need to update these studies by adding the new pest, S. frugiperda, in order to understand the effect of temperature on the larval interactions of all these four species under the context of climate change. The influence of temperature on intra- and interspecific larval interactions was studied using artificial stems kept at different constant temperatures (15 °C, 20 °C, 25 °C, and 30 °C) in an incubator and assessing survival and relative growth rates of each species in single and multi-species experiments. After the inclusion of FAW into the experiments, with regard to relative growth rates, both intra- and interspecific competition was observed among all four species. With regard to survival rates, cannibalism can also explain the intra- and interspecific interactions observed among all four species. Interspecific competition was stronger between the stemborers than between the FAW and the stemborers. Similar to lepidopteran stemborers, temperature affected both survival and relative growth rates of the FAW as well. Regardless of the temperature, C. partellus was superior in interspecific interactions shown by higher relative growth and survival rates. The results suggest that the FAW will co-exist with stemborer species along entire temperature gradient, though competition and/or cannibalism with them is weak. In addition, temperature increases caused by climate change is likely to confer an advantage to C. partellus over the fall armyworm and the other noctuids

A system dynamics model for pests and natural enemies interactions

Stemborers (Busseola fusca, Sesamia calamistis and Chilo partellus), the fall armyworm (Spodoptera frugiperda) and associated parasitoids constitute an interacting system in maize fields in Kenya. This work aims at developing and evaluating models that represent the evolution of those interactions by applying system thinking and system dynamics approaches with its archetypes [causal loop diagram (CLD), reinforcing (R) and balancing (B)] to analyse the population of these multi-species systems. The software Vensim PLE 8.0.9 was used to implement the models and carry out the simulations of single-and multi-species systems. The results showed that when a single pest species with its associated parasitoids interact with the host plant, the species was able to establish and sustain by cyclical relationship between populations of the pest and the associated parasitoids. However, in multi-pest species systems, dominance of S. frugiperda and C. partellus over B. fusca and S. calamistis was observed, but without extinction. However, there was a likelihood for B. fusca being displaced by C. partellus. Overall, the models predict the coexistence of fall armyworm with stemborer species as an additional pest of maize in Africa that need to be considered henceforth in designing IPM strategies in maize

Cannibalism and intraguild predation involved in the intra- and inter-specific interactions of the invasive fall armyworm, Spodoptera frugiperda, and lepidopteran maize stemborers

Cannibalism and intraguild predation can play important roles in determining spread and survival or death of organisms which share the same resource. However, the relationship between cannibalism and intraguild predation, and the costs and benefits of such behaviours, is difficult to establish within insect communities, and little is known about how such behaviours are affected by invasive species. The present study was aimed at assessing the interactions between larvae of fall armyworm (Spodoptera frugiperda) and maize stemborers (native to Africa, Busseola fusca, and Sesamia calamistis and native to India, Chilo partellus) in relation to cannibalism and intraguild predation when they utilize the same resource. Experiments involving treatments with either single species of S. frugiperda or any of the stemborers or pairwise species combinations with S. frugiperda were conducted under laboratory conditions. The experimental insect larvae were reared on maize leaves and monitored until the last developmental stage where cannibalism and/or intraguild predation, larval survival, and relative growth rate were recorded. Results of the intraspecific interaction indicated that S. frugiperda exhibited cannibalism to a larger degree than the stemborers species, especially at the late instars. The higher cannibalism trait in S. frugiperda turned, however, to competitive advantage as it led to a higher degree of intraguild predation when they cohabit with stemborer species and allowed FAW to gain a greater relative growth rate. Overall, interactions with FAW are detrimental for stemborer species and may be an important factor to explain the invasive success of S. frugiperda. Such knowledge is essential to understand the mechanisms behind ecological interactions between pests with overlapping niches in the field and in designing successful integrated pest management strategies

Caterpillar-induced plant volatiles attract conspecific and heterospecific adults for oviposition within a community of lepidopteran stemborers on maize plant

Olfactory cues may influence host plant preferences for oviposition of female moths within a community of stemborers that utilise the same resource. This study aimed to evaluate plant preferences for oviposition of gravid females of noctuid stemborers, Busseola fusca and Sesamia calamistis, and the crambid Chilo partellus for uninfested maize plants and plants infested by conspecific or heterospecific larvae. The involvement of volatile organic compounds (VOCs) emitted by uninfested and maize plants infested by conspecific or heterospecific larvae on moth orientation was studied in Y-tube olfactometer assays and in the field. All gravid female moths significantly preferred VOCs emitted by plants infested by conspecific or heterospecific larvae over those from uninfested plants, and female moths did not systematically prefer VOCs emitted by plants infested by conspecifics. Field trials confirmed these results. Chemical analysis by coupled gas chromatography/mass spectrometry showed that VOCs emitted by larvae-infested plants, regardless of the stemborer species, were compositionally richer than those released by uninfested plants but their emission intensity varied with species involved in the infestation. Busseola fusca larvae induced a compositionally richer VOCs profile than S. calamistis and C. partellus larvae. Eight candidate attractants were associated with larvae-infested plants. These results open new avenues to develop attractants specific to trap female stemborer moths in the field