Larval dispersal of the invasive fall armyworm, Spodoptera frugiperda, the exotic stemborer Chilo partellus, and indigenous maize stemborers in Africa

Larval dispersal either through ballooning or crawling results in a redistribution of the insect population and infestations within and between plants. In addition, invasive species, such as the fall armyworm (FAW), Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), and the exotic stemborer Chilo partellus (Swinhoe) (Lepidoptera: Crambidae), may displace indigenous stemborers on maize in Africa. To test whether larval dispersal activity may play a role in the displacement of indigenous stemborers, larval dispersal was compared between FAW, C. partellus, and the indigenous species Busseola fusca (Fuller) and Sesamia calamistis (Hampson) (both Lepidoptera: Noctuidae). Twenty potted maize plants were infested with one batch of eggs either from stemborers (B. fusca, S. calamistis, or C. partellus) or from FAW and monitored in the greenhouse for ballooning activities. After egg hatching, both ballooning and non-ballooning larvae were identified according to species and counted. FAW neonate larvae had greater potential for ballooning off than stemborers, irrespective of species. For each species, more females dispersed than males, and their survival rate was higher than that of non-ballooning larvae. In addition, plant-to-plant larval movements were studied using 6.25-m(2) plots of caged maize in a completely randomized design with five replicates. FAW was found to have wider dispersal and plant damage potential than any of the stemborer species. In conclusion, in contrast to C. partellus, the invasive characteristic of FAW can be explained, in part, by its higher larval dispersal activity compared to stemborers. This difference in larval dispersal might also be considered in sampling plans for monitoring pest density in the field

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

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 degrees C, 20 degrees C, 25 degrees C, and 30 degrees 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

Impact of the exotic fall armyworm on larval parasitoids associated with the lepidopteran maize stemborers in Kenya

Exotic invasive insect herbivores have the potential to interfere with existing herbivore-natural enemy interactions in new environments. Fall armyworm (FAW), Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), is a new invasive pest in maize fields in Africa. Understanding the acceptability and suitability of FAW to existing maize stemborer-parasitoid interactions is the first step in elucidating the impact that this exotic insect pest can have on the existing natural enemies used in biological control of maize stemborers in Kenya. The most commonly used larval parasitoids for biological control programs against maize stemborer communities in East Africa are Cotesia flavipes Cameron (Hymenoptera: Braconidae) and two populations of the native Cotesia sesamiae (Cs-Inland and Cs-Coast) Cameron (Hymenoptera: Braconidae). All these parasitoid species attacked FAW larvae but none yielded offspring, although they induced high non-reproductive host mortality when compared to natural mortality. Furthermore, the parasitoids that inserted their ovipositor into FAW larvae exhibited no significant preference between FAW larvae and their respective stemborer hosts under dual-choice bioassays. In olfactometer bioassays, the parasitoids were more attracted to plants infested by FAW than uninfested plants and even showed a marked preference for the odours of plants infested by FAW over those of plants infested by their natural host counterparts. This study illustrates that exotic pests, such as FAW, can impact existing stemborer-parasitoid interactions associated with maize, even if they cannot be used as hosts by parasitoids associated with these stemborers. Although additional studies are needed, FAW might therefore have a negative impact on stemborer biological control existing before its invasion

Biopesticide based sustainable pest management for safer production of vegetable legumes and brassicas in Asia and Africa

Published online: 10 May 2019Vegetables are one of the important crops which could alleviate the poverty and malnutrition among the smallholder farmers in tropical Asia and Africa. However, a plethora of pests limit the productivity of these crops, leading to economic losses. Vegetable producers overwhelmingly rely on chemical pesticides in order to reduce pest‐caused economic losses. However, over‐reliance on chemical pesticides poses serious threats to human and environmental health. Hence, biopesticides offer a viable alternative to chemical pesticides in sustainable pest management programs. Baculoviruses such as nucleopolyhedrovirus (NPV) and granulovirus (GV) have been exploited as successful biological pesticides in agriculture, horticulture and forestry. Maruca vitrata multiple nucleocapsid NPV (MaviMNPV) was found to be a unique baculovirus specifically infecting pod borer on food legumes, and it has been successfully developed as a biopesticide in Asia and Africa. Entomopathogenic fungi also offer sustainable pest management options. Several strains of Metarhizium anisopliae and Beauveria bassiana have been tested and developed as biopesticides in Asia and Africa. This review specifically focuses on the discovery and development of entomopathogenic virus and fungi‐based biopesticides against major pests of vegetable legumes and brassicas in Asia and Africa