Pest damage on Jatropha curcas (Euphorbiaceae): the effect of seedling irrigation in Sahelian Niger

Herbivory by insects and mites on physic nut (Jatropha curcas L.) seedlings was investigated and compared with irrigation in the semi-arid Sahelian Niger, utilizing a randomized complete block design experiment. Three water treatment protocols were applied and the types of damage were recorded. Less than 5% of the seedlings died during the 10-month trial period with sap suckers causing the most damage on the surviving plants. Plants with high production of biomass and leaf cover (foliage) were most strongly positively correlated with irrigation and were also the plants that endured the highest degree of herbivory. The low dieback may indicate that defence mechanisms counteract seedling herbivory and that drought-stressed plants invest more in their defence mechanism system than vital plants

Seasonal Variations of Spodoptera frugiperda Host Plant Diversity and Parasitoid Complex in Southern and Central Benin

Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) was recorded for the first time in 2016 attacking maize fields in central and west Africa. Soon after, several other regions and countries have reported the pest in almost the entire sub-Saharan Africa. In the present study, we assumed that (i) a variety of alternative plant species host FAW, especially during maize off-season, (ii) a wide range of local parasitoids have adapted to FAW and (iii) parasitoid species composition and abundance vary across seasons. During a two-year survey (from June 2018 to January 2020), parasitoids and alternative host plants were identified from maize and vegetable production sites, along streams and lowlands, on garbage dumps and old maize fields in southern and partly in the central part of Benin during both maize growing- and off-season. A total of eleven new host plant species were reported for the first time, including Cymbopogon citratus (de Candolle) Stapf (cultivated lemon grass), Bulbostylis coleotricha (A. Richard) Clarke and Pennisetum macrourum von Trinius (wild). The survey revealed seven parasitoid species belonging to four families, namely Platygastridae, Braconidae, Ichneumonidae, and Tachinidae associated with FAW on maize and alternative host plants. The most abundant parasitoid species across seasons was the egg parasitoid Telenomus remus (Nixon) (Hymenoptera: Platygastridae). These findings demonstrate FAW capability to be active during the maize off-season in the selected agro-ecologies and provide baseline information for classical and augmentative biocontrol efforts.Seasonal Variations of Spodoptera frugiperda Host Plant Diversity and Parasitoid Complex in Southern and Central BeninpublishedVersio

New ecological options for the management of horticultural crop pests in Sudano-Sahelian agroecosystems of west Africa

The agroecological approach to agroecosystem management relies on two pillars: vegetational diversification and soil biological activity enhancement. Although crop pests and their natural enemies may be diversely affected by measures derived from these principles, those generally result in increased agroecosystem resilience visà- vis both aerial and soil pests. Earlier studies by ICRISAT and CIRAD and their partners in West Africa showed the potential of the implementation of these principles for the management of some major pests of both staple food and horticultural crops, and their limitations for others, notably in the water-saving and income-generating systems mixing cereals, legumes, and high-value crops currently promoted in the Sudano-Sahelian zones, such as the drip irrigation-based African Market Garden (AMG) and the water harvesting-based Bio-Reclamation of Degraded Lands (BDL) systems. Pigeon-pea showed potential for trap-cropping tomato fruit worm (TFW) on okra, while Andropogon grass was dismissed for such management of stem-borer on pearl millet, and mixed results were obtained with castor bean and other potential trap crops for panicle-feeding bug management on sorghum. The results presented highlight the potential for mobilizing either aerial or soil-bound biological processes for managing fruit flies (FF), the main pest of grafted jujube tree, and leaf worm, the main pest of the Moringa tree, for sustainable production of these two major crops (in BDL and AMG systems, respectively), without having to rely on synthetic pesticide sprays. Studies on the social acceptability of the proposed management options (e.g., pigeon-pea in okra-based BDL) are also underway. The potential of the Jatropha shrub grown as a live-fence around these systems, either for its top-down effects or via the use of its extracts in an assisted push-pull strategy, is discussed. These studies on targeted pathosystems serve the dual purpose of finding solutions to local problems and contribute more globally to the design of pest resilient agrosystems

New ecological options for the management of horticultural crop pests in Sudano-Sahelian agroecosystems of west Africa

The agroecological approach to agroecosystem management relies on two pillars: vegetational diversification and soil biological activity enhancement. Although crop pests and their natural enemies may be diversely affected by measures derived from these principles, those generally result in increased agroecosystem resilience visà- vis both aerial and soil pests. Earlier studies by ICRISAT and CIRAD and their partners in West Africa showed the potential of the implementation of these principles for the management of some major pests of both staple food and horticultural crops, and their limitations for others, notably in the water-saving and income-generating systems mixing cereals, legumes, and high-value crops currently promoted in the Sudano-Sahelian zones, such as the drip irrigation-based African Market Garden (AMG) and the water harvesting-based Bio-Reclamation of Degraded Lands (BDL) systems. Pigeon-pea showed potential for trap-cropping tomato fruit worm (TFW) on okra, while Andropogon grass was dismissed for such management of stem-borer on pearl millet, and mixed results were obtained with castor bean and other potential trap crops for panicle-feeding bug management on sorghum. The results presented highlight the potential for mobilizing either aerial or soil-bound biological processes for managing fruit flies (FF), the main pest of grafted jujube tree, and leaf worm, the main pest of the Moringa tree, for sustainable production of these two major crops (in BDL and AMG systems, respectively), without having to rely on synthetic pesticide sprays. Studies on the social acceptability of the proposed management options (e.g., pigeon-pea in okra-based BDL) are also underway. The potential of the Jatropha shrub grown as a live-fence around these systems, either for its top-down effects or via the use of its extracts in an assisted push-pull strategy, is discussed. These studies on targeted pathosystems serve the dual purpose of finding solutions to local problems and contribute more globally to the design of pest resilient agrosystems

Global habitat suitability of Spodoptera frugiperda (JE Smith) (Lepidoptera, Noctuidae): key parasitoids considered for its biological control

Open Access Journal; Published online: 24 Mar 2021The present study is the first modeling effort at a global scale to predict habitat suitability of fall armyworm (FAW), Spodoptera frugiperda and its key parasitoids, namely Chelonus insularis, Cotesia marginiventris,Eiphosoma laphygmae,Telenomus remus and Trichogramma pretiosum, to be considered for biological control. An adjusted procedure of a machine-learning algorithm, the maximum entropy (Maxent), was applied for the modeling experiments. Model predictions showed particularly high establishment potential of the five hymenopteran parasitoids in areas that are heavily affected by FAW (like the coastal belt of West Africa from Côte d’Ivoire (Ivory Coast) to Nigeria, the Congo basin to Eastern Africa, Eastern, Southern and Southeastern Asia and some portions of Eastern Australia) and those of potential invasion risks (western & southern Europe). These habitats can be priority sites for scaling FAW biocontrol efforts. In the context of global warming and the event of accidental FAW introduction, warmer parts of Europe are at high risk. The effect of winter on the survival and life cycle of the pest in Europe and other temperate regions of the world are discussed in this paper. Overall, the models provide pioneering information to guide decision making for biological-based medium and long-term management of FAW across the globe

Harnessing data science to improve integrated management of invasive pest species across Africa: an application to Fall armyworm (Spodoptera frugiperda) (J.E. Smith) (Lepidoptera: Noctuidae)

Open Access Journal; Published online: 11 Feb 2022After five years of its first report on the African continent, Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) is considered a major threat to maize, sorghum, and millet production in sub-Saharan Africa. Despite the rigorous work already conducted to reduce FAW prevalence, the dynamics and invasion mechanisms of FAW in Africa are still poorly understood. This study applied interdisciplinary tools, analytics, and algorithms on a FAW dataset with a spatial lens to provide insights and project the intensity of FAW infestation across Africa. The data collected between January 2018 and December 2020 in selected locations were matched with the monthly average data of the climatic and environmental variables. The multilevel analytics aimed to identify the key factors that influence the dynamics of spatial and temporal pest density and occurrence at a 2 km x 2 km grid resolution. The seasonal variations of the identified factors and dynamics were used to calibrate rule-based analytics employed to simulate the monthly densities and occurrence of the FAW for the years 2018, 2019, and 2020. Three FAW density level classes were inferred, i.e., low (0–10 FAW moth per trap), moderate (11–30 FAW moth per trap), and high (>30 FAW moth per trap). Results show that monthly density projections were sensitive to the type of FAW host vegetation and the seasonal variability of climatic factors. Moreover, the diversity in the climate patterns and cropping systems across the African sub-regions are considered the main drivers of FAW abundance and variation. An optimum overall accuracy of 53% was obtained across the three years and at a continental scale, however, a gradual increase in prediction accuracy was observed among the years, with 2020 predictions providing accuracies greater than 70%. Apart from the low amount of data in 2018 and 2019, the average level of accuracy obtained could also be explained by the non-inclusion of data related to certain key factors such as the influence of natural enemies (predators, parasitoids, and pathogens) into the analysis. Further detailed data on the occurrence and efficiency of FAW natural enemies in the region may help to complete the tri-trophic interactions between the host plants, pests, and beneficial organisms. Nevertheless, the tool developed in this study provides a framework for field monitoring of FAW in Africa that may be a basis for a future decision support system (DSS)

Seasonal Variations of Spodoptera frugiperda Host Plant Diversity and Parasitoid Complex in Southern and Central Benin

Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) was recorded for the first time in 2016 attacking maize fields in central and west Africa. Soon after, several other regions and countries have reported the pest in almost the entire sub-Saharan Africa. In the present study, we assumed that (i) a variety of alternative plant species host FAW, especially during maize off-season, (ii) a wide range of local parasitoids have adapted to FAW and (iii) parasitoid species composition and abundance vary across seasons. During a two-year survey (from June 2018 to January 2020), parasitoids and alternative host plants were identified from maize and vegetable production sites, along streams and lowlands, on garbage dumps and old maize fields in southern and partly in the central part of Benin during both maize growing- and off-season. A total of eleven new host plant species were reported for the first time, including Cymbopogon citratus (de Candolle) Stapf (cultivated lemon grass), Bulbostylis coleotricha (A. Richard) Clarke and Pennisetum macrourum von Trinius (wild). The survey revealed seven parasitoid species belonging to four families, namely Platygastridae, Braconidae, Ichneumonidae, and Tachinidae associated with FAW on maize and alternative host plants. The most abundant parasitoid species across seasons was the egg parasitoid Telenomus remus (Nixon) (Hymenoptera: Platygastridae). These findings demonstrate FAW capability to be active during the maize off-season in the selected agro-ecologies and provide baseline information for classical and augmentative biocontrol efforts

Minimal effects on genetic structuring of a fungus‐dwelling saproxylic beetle after recolonisation of a restored forest

Habitat restoration aims to improve local habitat conditions for threatened species. While such restorations are widespread, rigorous evaluations of their success are rare. This is especially true of those considering species dynamics. Increasingly, deadwood is a target for forest restoration as many species directly and indirectly depend on this resource. In a broadleaf forest in southern Germany, we explored the effect of landscape‐wide deadwood restoration on the population genetic structure of the specialist fungus‐dwelling saproxylic beetle Bolitophagus reticulatus. Before 2003, the northern area of this forest was intensively logged for more than half a century, while the southern part was less intensively managed. This drove populations of the host fungus Fomes fomentarius, and consequently the beetle, to local extinction in the northern part. Only after the first decade of restoration were both the fungus and its beetles present across all areas of the forest. Using 17 newly developed microsatellite loci, we show that these beetles exhibit population genetic structuring, mainly influenced by the north‐south divide. However, the low degree of isolation‐by‐distance, and the low relatedness of beetles collected from the same trees or fungus, shows that strong dispersal ability is facilitating the recolonisation of these forests on the scale of tens of kilometers. In another 10 years, it is likely that the population will show even less genetic structuring. Synthesis and applications. Through the recolonisation of the fungus Fomes fomentarius and the fungus‐dwelling beetle Bolitophagus reticulatus after deadwood restoration, we demonstrate that, while there are many discussions on the optimal spatial distribution of deadwood, just the presence of deadwood can be sufficient to enable recolonisations of specific species. As long as some relict populations of these species are embedded in a once intensively managed forest, increased deadwood (amount and diversity) anywhere will benefit recolonisation of the habitat. However, increasing deadwood diversity should also be encouraged to benefit even more species

Global Habitat Suitability of Spodoptera frugiperda (JE Smith) (Lepidoptera, Noctuidae): Key Parasitoids Considered for Its Biological Control

Simple Summary: The fall armyworm (FAW), Spodoptera frugiperda has now become a pest of global importance. Its introduction and detection in Africa in 2016, and subsequent introduction and spread into Asia and Australia, has put several millions of food producers and maize farmers at risk. Not all pest management strategies are sustainable. Biological control with the use of parasitoid wasps is one of the durable and environmentally sound options. The present study was initiated to predict the habitats of high establishment potential of key parasitoids of FAW in South America, which might prove to be effective as classical biological control agents of FAW in regions where it is an invasive species under current and future climate scenarios. The prospective parasitoids are the following: Chelonus insularis, Cotesia marginiventris, Eiphosoma laphygmae, Telenomus remus and Trichogramma pretiosum. The results demonstrate overlapping habitat suitability areas of the pest and the parasitoids, suggesting promises for biological control options for the management of FAW under current and future climate scenarios. Abstract: The present study is the first modeling effort at a global scale to predict habitat suitability of fall armyworm (FAW), Spodoptera frugiperda and its key parasitoids, namely Chelonus insularis, Cotesia marginiventris, Eiphosoma laphygmae, Telenomus remus and Trichogramma pretiosum, to be considered for biological control. An adjusted procedure of a machine-learning algorithm, the maximum entropy (Maxent), was applied for the modeling experiments. Model predictions showed particularly high establishment potential of the five hymenopteran parasitoids in areas that are heavily affected by FAW (like the coastal belt of West Africa from Côte d’Ivoire (Ivory Coast) to Nigeria, the Congo basin to Eastern Africa, Eastern, Southern and Southeastern Asia and some portions of Eastern Australia) and those of potential invasion risks (western & southern Europe). These habitats can be priority sites for scaling FAW biocontrol efforts. In the context of global warming and the event of accidental FAW introduction, warmer parts of Europe are at high risk. The effect of winter on the survival and life cycle of the pest in Europe and other temperate regions of the world are discussed in this paper. Overall, the models provide pioneering information to guide decision making for biological-based medium and long-term management of FAW across the globe