The Efficacy of Selected Synthetic Insecticides and Botanicals against Fall Armyworm, Spodoptera frugiperda, in Maize

Abstract

Fall armyworm (FAW) was reported for the first time in Africa in 2016. FAW is widely distributed in Ethiopia, causing significant damage to maize. Nine synthetic insecticides belonging to different chemical groups and 11 pesticidal plants (botanicals) were tested for their efficacy against FAW under laboratory, greenhouse, and field conditions. In the laboratory, Radiant, Tracer, Karate, and Ampligo caused over 90% larval mortality 72 h after application. Malathion had moderate activity, causing 51.7% mortality 72 h after application, while Carbaryl was less effective, causing 28% mortality 72 h after application. In the greenhouse experiment, all synthetic insecticides reduced foliar damage to maize compared to the untreated control. Chemical sprays did not affect plant height, stem thickness, or leaf number. The highest fresh weight (471 g) was obtained from plants treated with Radiant. Among the botanicals tested, Azadirachta indica, Schinnus molle, and Phytolacca dodecandra resulted in the highest percentage larval mortality (>95%) 72 h after application. In the field, non-treated control plants showed extensive leaf injury compared to the synthetic insecticide- and botanical-treated plants. The synthetic insecticides and botanicals that showed high efficacy against FAW larvae can be used as components for integrated pest management (IPM) plans for FAW under smallholder farmer conditions in Ethiopia and elsewhere in Africa.

Diamide resistance: 10 years of lessons from lepidopteran pests

“…Very few studies have reported on insecticide control efficacy since the spread. One study in Ethiopia reported close to baseline susceptibility towards diamides and several other insecticide classes (Sisay et al 2019). If true, this is extremely fortunate, and is probably accounted for by an extreme genetic bottleneck in the founders of the Afro-Asian population, in which insufficient genetic diversity was present for resistance to emerge (Day et al 2017).…”

Opportunities and Scope for Botanical Extracts and Products for the Management of Fall Armyworm (Spodoptera frugiperda) for Smallholders in Africa

“…A high mortality of FAW was reported with extracts of Jatropha curcas, Militia ferruginea, Phytolacca dodecandra, Scinus molle, Melia abyssinica, Nicotiana tabacum, Lantana camara, Chenopodium ambroides, Azadirachta indica and Jatropha gossypifolia [26]. This is the first report where these plant species were evaluated against FAW in Africa-Ethiopia.…”

“…Mortality, decreased pupal weight [26,27] Anacardiaceae Schinus molle L. High mortality [26] Annonaceae Annona squamosa L. Decreased pupa weight, increased larval mortality [33] Apiaceae Zingiberaceae Zingiber officinale L. Mortality [36] The essential oil of Cymbopogon flexuosus was reported to be lethal to FAW (LC 50 = 1.35 mg Ll −1 ) when supplemented in to an artificial diet at 2.25, 2.5 and 4 mg Ll −1 concentrations and 18.85 h median lethal time (LT 50 ). The insecticidal activity of citral was not significantly different to the essential oil, suggesting that citral, a compound of this essential oil caused insecticidal effects of the Cymbopogon flexuosus essential oil to FAW [80].…”

“…Similarly, Dysphania (syn. Chenopodium) ambrosioides (L.) Mosyakin & Clemants, has been shown to be biologically active vs FAW [26,27] but is also considered for use in Africa [28], while species such as Corymbia (syn. Eucalyptus) citriodora (Hook.)…”

“…The opportunities maybe limited in scope where the products are not standardized for reproducibility and scale-up and this will require uniformity of the chemistry for the plant material and they likely need propagation [87,106]. More so, surprisingly few have been evaluated under field conditions [26]. This is a major oversight of the work as it means there is little evidence that any of the biological activities translate to a real-world setting.…”