Abstract
The fall armyworm (FAW), Spodoptera frugiperda (Smith), is a major pest native to the Americas. A recent invasion of FAWs from Africa eastward to South Asia, the Indochina Peninsula, and mainland China has received much attention due to the considerable economic losses in agriculture. FAWs can rapidly colonise a new area, likely due to the wide range of host plants, good flying capability, and high egg production. Therefore, a convenient, quick, and accurate tool for FAW identification is urgently required to establish a FAW invasion management strategy. In this study, FAW-specific primers were designed to recognise FAWs on the basis of internal transcribed spacer 1 (ITS1). The results revealed the accurate FAW recognition of the three congeneric species and eight common corn lepidopteran pests, especially at their larval stage. Furthermore, species-specific primers have confirmed their efficacy by using 69 FAW specimens from Taiwan, Thailand, and the United States, with a 96% success rate, excluding 3 decayed specimens. By using the simple, reliable, and convenient FAW-specific primers, a pest management programme can be developed not only to reduce sequencing costs and experimental time from 2 days to 4 h, but eradicate the FAW as soon as it enters a new area.
Highlights
The fall armyworm (FAW), Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), is a major pest native to the Americas with wide distribution from Canada to Argentina[1,2]
Evidence from amplified fragment length polymorphisms (AFLPs) has revealed that two to five genetically distinct clusters existed in FAWs22; distinguishing the corn strain from rice strain based on their host plant is not feasible
The DNA concentration dilution tests, which mimicked the DNA amounts of different field specimens, affirmed that the failure of Polymerase chain reaction (PCR) amplification of 28S rDNA in these specimens was due to their spoiled status, the DNA concentration diluted > 100X
Summary
The fall armyworm (FAW), Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), is a major pest native to the Americas with wide distribution from Canada to Argentina[1,2]. The damage caused by FAWs to economically essential crops such as maize, sorghum, rice, and sugarcane was estimated to be $13,383 million annually in A frica[8]. The migratory capability and wide range of host plants increase the survival possibility of highly reproductive FAW when it colonises in a new area, either through natural migration or anthropogenic activities. In 2016, FAWs became notorious after their invasion of Nigeria and G hana[9,10] and rapid intrusion, within 2 years, into > 20 sub-Saharan countries, causing severe economic losses of crops in A frica[11]. Taxonomic identification of FAW is generally difficult due to the co-occurrence of morphologically similar larvae of Spodoptera spp. in crops, recognition of adult species is feasible. Developing specific primers will be helpful to survey FAWs in pest-free countries because the transition of a FAW from larva to adult requires approximately 30 d ays[1,31]
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