Analysis of strain distribution, migratory potential, and invasion history of fall armyworm populations in northern sub-Saharan Africa

Open Access Journal; Published online: 27 Feb 2018Fall armyworm (Spodoptera frugiperda J.E. Smith) is a noctuid moth pest endemic throughout the Western Hemisphere that has recently become widespread in sub-Saharan Africa. There is a strong expectation of significant damage to African maize crop yield and a high likelihood of further dispersal, putting the rest of the Eastern Hemisphere at risk. Specimens from multiple locations in six countries spanning the northern portion of the infested region were analyzed for genetic markers. The similarity of haplotypes between the African collections was consistent with a common origin, but significant differences in the relative frequency of the haplotypes indicated limitations in migration. The mitochondrial marker frequently used to identify two host strains appears to be compromised, making uncertain previous reports that both strains are present in Africa. This more extensive study confirmed initial indications based on Togo populations that Florida and the Greater Antilles are the likely source of at least a subset of the African infestation and further suggest an entry point in western Africa. The origin of a second subgroup is less clear as it was rarely found in the collections and has a haplotype that has not yet been observed in the Western Hemisphere

Postharvest insect infestation in maize grain stored in woven polypropylene and in hermetic bags

Maize was artificially infested with either 10 or 25 individual Prostephanus truncatus (Horn) and Sitophilus zeamais (Motschulsky) or a mixture of both, and stored in a hermetic grain bag (HGB) or a woven polypropylene bag (WPB) for 150 days. Population growth of P. truncatus and S. zeamais during storage was low in HGB, while in WPB, the insect population increased significantly with storage duration. Mortality rate during storage was significantly higher in HGB than in WPB. After 60 days of storage, the average mortality rate of 99.50% was observed in HGB infested with 25 P. truncatus, and 100% for S. zeamais at the same infestation density after 90 days of storage. Grain losses were significantly lower in HGB compared with WPB. Less than 0.5 and 6.0% losses were obtained, respectively, for S. zeamais and P. truncatus in HGB infested with 25 individual insects after 150 days of storage, whereas losses of 19.2% (infestation with S. zeamais) and 27.1% (infestation with P. truncatus) were observed in WPB. HGB seems to be resistant to the perforation of S. zeamais, but not to P. truncatus. The moisture content of maize grains stored in HGB remained practically the same during storage, compared with the levels in WPB, which reduced with storage time. WPB could be used for maize storage, protecting it against insect infestation without the need for insecticide use

The effect of leguminous cover crops and cowpea planted as border rows on maize ear borers with special reference to Mussidia nigrivenella Ragonot (Lepidoptera: Pyralidae)

In southern Benin, the use of cover crops to improve and maintain soil fertility is on the increase. The present study investigated the effect of two leguminous cover crops, Canavalia ensiformis (L.) DC and Sesbania rostrata Brem. & Oberm., planted at different dates before maize (Zea mays (L.)), and cowpea (Vigna unguiculata L.) planted as border rows on infestations of maize by the pyralid Mussidia nigrivenella Ragonot and of other cob-boring lepidopteran pests. In both trials, M. nigrivenella densities at harvest tended to be higher in the maize alone than the legume treatments, but the effect depended on the timing of planting of the cover crop in relation to that of maize. There were no discernible trends for other borers such as the noctuid Sesamia calamistis Hampson, the pyralid Eldana saccharina Walker, and the tortricid Thaumatotibia leucotreta Meyrick. Furthermore, M. nigrivenella pest loads were considerably higher on C. ensiformis than maize, indicating that the presence of alternative host plant species in the vicinity of maize fields did not increase M. nigrivenella attack on maize. Though in some of the legume treatments, grain damage and grain losses were higher than in the maize alone plots, per area yields did not vary significantly.In southern Benin, the use of cover crops to improve and maintain soil fertility is on the increase. The present study investigated the effect of two leguminous cover crops, Canavalia ensiformis (L.) DC and Sesbania rostrata Brem. & Oberm., planted at different dates before maize (Zea mays (L.)), and cowpea (Vigna unguiculata L.) planted as border rows on infestations of maize by the pyralid Mussidia nigrivenella Ragonot and of other cob-boring lepidopteran pests. In both trials, M. nigrivenella densities at harvest tended to be higher in the maize alone than the legume treatments, but the effect depended on the timing of planting of the cover crop in relation to that of maize. There were no discernible trends for other borers such as the noctuid Sesamia calamistis Hampson, the pyralid Eldana saccharina Walker, and the tortricid Thaumatotibia leucotreta Meyrick. Furthermore, M. nigrivenella pest loads were considerably higher on C. ensiformis than maize, indicating that the presence of alternative host plant species in the vicinity of maize fields did not increase M. nigrivenella attack on maize. Though in some of the legume treatments, grain damage and grain losses were higher than in the maize alone plots, per area yields did not vary significantly

Interactions variations climatiques – insectes ravageurs et perception des producteurs de cereales au sud Togo

La présente étude se propose d'établir les données de base relatives aux facteurs déterminants responsables de la structuration des espèces et procéder à des analyses qui permettront de déterminer la distribution des insectes ravageurs du maïs avec les prévisions actuelles des changements climatiques. De façon générale, le foreur de tige Sesamia calamistis a été l’espèce la plus rencontrée dans toutes les zones prospectées avec une abondance de 76,02% suivi de Busseola fusca (21,7%) et de Eldana saccharina (2,3%). Les projections d’une hausse des températures au Togo entraineraient de légères augmentations annuelles d’au moins + 0,23 des générations de S. calamistis et de E. saccharina. De plus l’analyse de la perception des agriculteurs indique l’apparition de «nouveaux» ravageurs tels que les termites, le criquet puant Zonocerus variegatus et une recrudescence des ravageurs de stock.Mots clés: Changements climatiques, Sesamia calamistis, maïs, générations, termitesEnglish Title: Climate variations-insect pests interactions and perception of cereal producers in southern TogoEnglish AbstractThe present study seeks to establish baseline data on the determinants responsible for the structuring of species and conduct analyzes that will determine the distribution of insect pests of maize under projected climate change. In general, stem borer Sesamia calamistis was the most important species found in all surveyed areas with an abundance of 76.02% followed by Busseola fusca (21.7%) and Eldana saccharina (2.3%). The result showed that projected increasing temperatures in Togo will probably lead to slight annual increases of at least +0.23 in number of S. calamistis and E. Saccharina generations. Further analysis of the perception of farmers indicates the proliferation of "new" pests such as termites, Zonocerus variegatus and an increase in storage insect pests.Keywords: Climate change, Sesamia calamistis, maize, generations, termite

Interaction between the aphid parasitoid Lysiphlebus testaceipes (Hymenoptera: Aphidiidae) and its hyperparasitoid Syrphophagus africanus (Hymenoptera: Encyrtidae)

The interactions between the cowpea aphid Aphis craccivora Koch, its parasitoid Lysiphlebus testaceipes Cresson and hyperparasitoid Syrphophagus africanus Gahan were assessed in the laboratory. Host age preference for hyperparasitism was evaluated using parasitized aphids of different ages (i.e. 1, 2, 3, 4, 5 and 6 days old and mixed ages). We studied the influence of the hyperparasitoid on the parasitism efficiency of L. testaceipes, the effect of host age on some biological parameters of S. africanus, and its hyperparasitism based on aggregated or isolated mummies. The presence of S. africanus significantly affected aphid parasitism by L. testaceipes (21.2 ^ 3.6 vs 36.6 ^ 4.5%). Except for 1-day-old hosts, S. africanus successfully parasitized hosts of all tested ages, with preference for newly formed mummies (39.16 ^ 3.31% parasitism in 5-day-old hosts). The development time of immature stages of the S. africanus progeny was significantly affected by host age. The sex ratio of the hyperparasitoid progeny was largely female biased and did not vary with host age. Syrphophagus africanus females from live parasitized aphids produced more offspring (36.55 ^ 6.28 vs 25.00 ^ 7.16) and lived longer (21.09 ^ 1.57 vs 10.88 ^ 2.31 days) than those from mummy hosts. Hyperparasitism rates were higher on aggregated mummies than on dispersed ones (36.00 ^ 2.86 vs 20.66 ^ 4.00%)

Evaluation du potentiel bioprotecteur des champignons mycorhiziens arbusculaires contre les nematodes phytoparasites et les insectes ravageurs du riz au Togo

Les insectes et les nématodes constituent une entrave à la production du riz. L'utilisation des Champignons Mycorhiziens Arbusculaires (CMA) serait une option non seulement de gestion efficiente de la fertilité des sols mais aussi de contrôle de ces ravageurs. Le but de cette étude a été donc de tester l'efficacité des CMA sur la réduction de la densité des nématodes et sur la dynamique des insectes ravageurs du riz. L'expérience a consisté à inoculer sur sol stérilisé des semences de riz en pépinière avec quatre souches de CMA (Acaulospora spinosa, Ben 10, Glomus mosseae et de G. hoï) testées à trois doses d’inoculation (7,82 x 105; 3,91 x 105 et 1,96 x 105 spores/ha). Les plants non fertilisés et non mycorhizés (témoin absolu) et les plants fertilisés aux engrais chimique NPK 15 15 15 et Urée 46% N à la dose recommandée de 200 kg/ha et 100 kg/ha (témoin relatif), ont servi de témoins. Les résultats ont montré des corrélations négatives significatives entre la fréquence de mycorhization et la production de panicules non fertiles et une corrélation négative entre l’intensité de mycorhization des racines et la densité de nématodes aussi bien dans les racines que dans le sol. La symbiose mycorhizienne entre les CMA et les plants de riz n'ont pas empêché les insectes d'infester les plants mycorhizés. Toutefois l‘incidence des attaques des insectes a été significativement réduite sur les plants inoculés comparés aux plants sans mycorhizes ni engrais chimique. Les mycorhizes auraient permis en effet aux plants mycorhizés de mieux tolérer les attaques des insectes ravageurs comparés aux plants témoins.Il ressort de cette étude que les CMA seraient une bonne alternative aux nématicides et insecticides chimiques de synthèse dans la gestion des ravageurs en production rizicole. Les résultats sont discutés dans un esprit de l’utilisation des Champignons Mycorhiziens Arbusculaires comme stratégie de gestion écologique durable des bioagresseurs des cultures.Mots clés: Riz, champignons mycorhiziens arbusculaires, insectes ravageurs, nématodes phytoparasites, gestion écologique durableEnglish Title: Evaluation of the bioprotection potential of mycorrhizal arbuscular fungi against plant parasitic nematodes and insect pests of rice in TogoEnglish AbstractInsects and nematodes are an impediment to rice production. The use of Arbuscular Mycorrhizal Fungus (AMF) would be an option not only for the efficient management of soil fertility but also for the control of insect pests and plant parasitic nematodes. The aim of this study was to test the effectiveness of AMF in reducing nematode density and the insect pest damages. The experiment consisted in inoculating rice seeds on sterilized soil in nursery with four strains of AMF (Acaulospora spinosa, Ben 10, Glomus mosseae and G. hoï) tested at three spore concentrations (7,82 x 105 spores, 3.91 x 105 spores and 1.96 x 105 spores/ha). Plots planted with non-inoculated rice seedling that did not received any fertilizer (absolute control) and plots with plant fertilized with NPK 15 15 15 and Urea 46% N at the recommended rate of 200kg/ha and 100kg/ha, were used as controls. The results showed significant negative correlations between the frequency of mycorhization and non-fertile panicle production, and a negative correlation between root mycorrhizal intensity and nematode density both in the roots and soil. The mycorrhizal symbiosis between tested AMF and rice plants did not prevent insects from infesting inoculated plants. However, incidence of insect attack was significantly lower in inoculated plants compared to plants without AMF or chemical fertilizer. The AMF might have allowed inoculated plants to more tolerate the attacks of insect pests compared to non-inoculated one.It appears from this study that AMF could be a good alternative to synthetic nematicides and chemical insecticides in pest management in rice production. The results are discussed in the terms of using Arbuscular Mycorrhizal Fungi as a strategy for sustainable ecological management of crop pests.Keywords: Rice, Arbuscular Mycorrhizal Fungi, insect pests, plant parasitic nematodes, sustainable ecological managemen

Influence of rearing substrates and nontarget hosts on the bionomics of the Tachinid parasitoid Nemorilla maculosa (Diptera: Tachinidae).

Published online: 15 Feb 2018The tachinid Nemorilla maculosa Meigen (Diptera: Tachinidae) was introduced from Taiwan to Benin for evaluating its potential as a biocontrol candidate against the cowpea pest Maruca vitrata (Fabricius) (Lepidoptera: Crambidae). To optimize its rearing, we assessed the influence of M. vitrata larval age and rearing substrate—cowpea germinating grains and peabush leaves—on its life table parameters, while its host specificity was investigated with regard to nontarget effects. Parasitism rates were higher when older larvae (10- and 14-d old) were offered to females of N. maculosa compared to the younger (2-, 4-, and 6-d old) host larvae. Regardless of the rearing substrate, development time was longer for females than males, and females lived longer than males irrespective of the age of the host. Sex ratio did not vary significantly with host ages or rearing substrate. The average number of eggs laid by a female reared from M. vitrata larvae feeding on cowpea germinating grains or peabush leaves was 94.2 ± 4.38 and 71.9 ± 1.70 eggs, respectively. The host suitability of N. maculosa was assessed by testing four nontarget Lepidoptera species: Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae), Sesamia calamistis Hampson (Lepidoptera: Noctuidae), Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae), and Eldana saccharina Walker (Lepidoptera: Pyralidae). Larvae of S. littoralis and C. cephalonica were successfully parasitized while N. maculosa did not develop in the larvae of E. saccharina and S. calamistis although they were parasitized. Despite the potential of N. maculosa as a biological control agent against the pod borer M. vitrata, more detailed nontarget studies, extending to other native Crambidae species, are needed before making decisions on field releases

Combined activity of Maruca vitrata multinucleopolyhedrovirus, MaviMNPV, and oil from neem, Azadirachta indica Juss and Jatropha curcas L., for the control of cowpea pests

The insecticidal activity of Maruca vitrata (F.) multi-nucleopolyhedrovirus ( Mavi MNPV) combined with oil from neem, Azadirachta indica Juss and Jatropha curcas L. (Euphorbiaceae) was studied under labo- ratory and fi eld conditions against three key insect pests of cowpea, Vigna unguiculata (L.) Walp. Second- instar Aphis craccivora Koch and Megalurothirps sjostedti Trybom nymphs, and third-instar M. vitrata larvae, all from laboratory colonies, were treated with various concentrations of one of the control agents separately or combined. Daily mortality was recorded for fi ve days ( A. craccivora and M. sjostedti nymphs) or fourteen days ( M. vitrata ) and the larval and pupal development as well as adult emergence were assessed. Combination of Mavi MNPV resulted in a signi fi cantly higher larval mortality in M. vitrata than treatment with either virus or botanical insecticide alone at the corresponding concentrations. Larvae of M. vitrata infected with Mavi MNPV and treated with botanical oils died sooner than those infected with only one control agent. Combinations of Mavi MNPV and botanical oils produced additive or synergistic effects. No evidence of antagonistic effects was noted. In fi eld experiments, the application of botanical insecticide and Mavi MNPV either alone or in combination was effective in reducing insect abundance over the four weeks, and preventing yield loss. In the fi rst fi eld season, where the M. vitrata population was higher, the combination of the virus and either of the botanical pesticides induced signi fi cantly higher yields than spraying chemical insecticide. Application of Mavi MNPV in combination with J. curcas and A. indica oil has proven to induce consistent Mavi MNPV infection in M. vitrata populations. The combined application of Mavi MNPV and botanical oils is discussed in the context of integrated pest management.The insecticidal activity of Maruca vitrata (F.) multi-nucleopolyhedrovirus ( Mavi MNPV) combined with oil from neem, Azadirachta indica Juss and Jatropha curcas L. (Euphorbiaceae) was studied under labo- ratory and fi eld conditions against three key insect pests of cowpea, Vigna unguiculata (L.) Walp. Second- instar Aphis craccivora Koch and Megalurothirps sjostedti Trybom nymphs, and third-instar M. vitrata larvae, all from laboratory colonies, were treated with various concentrations of one of the control agents separately or combined. Daily mortality was recorded for fi ve days ( A. craccivora and M. sjostedti nymphs) or fourteen days ( M. vitrata ) and the larval and pupal development as well as adult emergence were assessed. Combination of Mavi MNPV resulted in a signi fi cantly higher larval mortality in M. vitrata than treatment with either virus or botanical insecticide alone at the corresponding concentrations. Larvae of M. vitrata infected with Mavi MNPV and treated with botanical oils died sooner than those infected with only one control agent. Combinations of Mavi MNPV and botanical oils produced additive or synergistic effects. No evidence of antagonistic effects was noted. In fi eld experiments, the application of botanical insecticide and Mavi MNPV either alone or in combination was effective in reducing insect abundance over the four weeks, and preventing yield loss. In the fi rst fi eld season, where the M. vitrata population was higher, the combination of the virus and either of the botanical pesticides induced signi fi cantly higher yields than spraying chemical insecticide. Application of Mavi MNPV in combination with J. curcas and A. indica oil has proven to induce consistent Mavi MNPV infection in M. vitrata populations. The combined application of Mavi MNPV and botanical oils is discussed in the context of integrated pest management.The insecticidal activity of Maruca vitrata (F.) multi-nucleopolyhedrovirus ( Mavi MNPV) combined with oil from neem, Azadirachta indica Juss and Jatropha curcas L. (Euphorbiaceae) was studied under labo- ratory and fi eld conditions against three key insect pests of cowpea, Vigna unguiculata (L.) Walp. Second- instar Aphis craccivora Koch and Megalurothirps sjostedti Trybom nymphs, and third-instar M. vitrata larvae, all from laboratory colonies, were treated with various concentrations of one of the control agents separately or combined. Daily mortality was recorded for fi ve days ( A. craccivora and M. sjostedti nymphs) or fourteen days ( M. vitrata ) and the larval and pupal development as well as adult emergence were assessed. Combination of Mavi MNPV resulted in a signi fi cantly higher larval mortality in M. vitrata than treatment with either virus or botanical insecticide alone at the corresponding concentrations. Larvae of M. vitrata infected with Mavi MNPV and treated with botanical oils died sooner than those infected with only one control agent. Combinations of Mavi MNPV and botanical oils produced additive or synergistic effects. No evidence of antagonistic effects was noted. In fi eld experiments, the application of botanical insecticide and Mavi MNPV either alone or in combination was effective in reducing insect abundance over the four weeks, and preventing yield loss. In the fi rst fi eld season, where the M. vitrata population was higher, the combination of the virus and either of the botanical pesticides induced signi fi cantly higher yields than spraying chemical insecticide. Application of Mavi MNPV in combination with J. curcas and A. indica oil has proven to induce consistent Mavi MNPV infection in M. vitrata populations. The combined application of Mavi MNPV and botanical oils is discussed in the context of integrated pest management

Bionomics of the parasitoid Apanteles taragamae as influenced by different diets fed to its host, Maruca vitrata

Published online: 18 October 2013