Abstract
Fall Armyworm (FAW) (Spodoptera frugiperda) is a polyphagous and highly destructive pest of many crops. It was recently introduced into Africa and now represents a serious threat to food security, particularly because of yield losses in maize, which is the staple food for the majority of small-scale farmers in Africa. The pest has also led to increased production costs, and threatens trade because of quarantines imposed on produce from the affected countries. There is limited specific knowledge on its management among smallholders since it is such a new pest in Africa. Some synthetic insecticides have been shown to be effective in controlling FAW, but in addition to the economic, health and environmental challenges of pesticide use insecticide resistance is highly prevalent owing to years of FAW management in the Americas. Therefore, there is a need for the development and use of alternatives for the management of FAW. These include plant-derived pesticides. Here we review the efficacy and potential of 69 plant species, which have been evaluated against FAW, and identify opportunities for use among small-scale maize farmers with a focus on how pesticidal plants might be adopted in Africa for management of FAW. The biological activities were diverse and included insecticidal, insectistatic (causing increased larval duration), larvicidal, reduced growth and acute toxicity (resulting in adverse effects within a short time after exposure). While most of these studies have been conducted on American plant taxa many South American plants are now cosmopolitan weeds so these studies are relevant to the African context.
Highlights
Fall Armyworm (FAW) (Spodoptera frugiperda Hurst) (Lepidoptera: Noctuidae) is a highly polyphagous pest having been reported on more than 80 species in 23 families [1] including cotton (Gossypium hirsutum L.) (Malvales: Malvaceae), corn (Zea mays L.) (Cyperales: Poaceae) and many other grass crops [2]
In comparison with the African armyworm (Spodoptera exempta), FAW larvae have unique mouthparts with notched cutting edges, enabling it to feed on flora
We review existing research on plant extracts that have been evaluated for the management of FAW with the aim of identifying those with potential for use by small-scale farmers in Africa, or informing approaches to identifying and evaluating untested native African plant taxa since pesticidal plants are already used as crudely produced products among smallholder farming communities in Africa with notable success [20,21,22]
Summary
Fall Armyworm (FAW) (Spodoptera frugiperda Hurst) (Lepidoptera: Noctuidae) is a highly polyphagous pest having been reported on more than 80 species in 23 families [1] including cotton (Gossypium hirsutum L.) (Malvales: Malvaceae), corn (Zea mays L.) (Cyperales: Poaceae) and many other grass crops [2]. While the use of chemical pesticides dominates existing approaches [7], several alternative control options exist and are being considered including resistant varieties [8,9,10], biological control [11,12], crop management practices [13,14], plant diversity [14], and mechanical methods [15]. None of these methods has yet delivered a viable option for effective control of FAW, the search for alternative approaches including those from plant extracts and their products. Hill & L.A.S.Johnson are widespread in both Africa and America but non-native and have been evaluated for activity against FAW [29]
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