Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) in Cameroon: Case study on its distribution, damage, pesticide use, genetic differentiation and host plants

Abstract

Maize farmers in sub-Saharan Africa recently experienced unusual damage in their farms, attributed to the fall armyworm (FAW) Spodoptera frugiperda (J. E. Smith). This pest was first recorded in Africa in 2016, but detailed information on its distribution and damage and farmer’s response in invaded areas are largely lacking. In this study, we determined FAW distribution, genetic diversity, host plants, crop damage, and farmers’ responses. S . frugiperda was recorded in the 10 regions of Cameroon. Average percentage of infested plants and damage severity (on a scale of 1 to 5) were lowest—20.7 ± 7.4% and 2.1 ± 0.1 respectively—in the Sahelian regions and greatest—69.0 ± 4.3% and 3.1 ± 0.1 respectively—in the Western Highlands. Altitude did not influence FAW incidence and severity and its larvae infrequently co-occurred with maize stemborers on the same plants, suggesting possible direct and/or indirect competition between the two groups of maize pests. In response to this new threat to maize production, farmers have opted for the application of synthetic pesticides. Although our experiments were not designed to determine pesticide efficacy, as parameters such as time since application were not considered, our observations suggest lack of a drastic effect on S . frugiperda infestations on maize. There were two haplotypes of FAW co-occurring in Cameroon corresponding to the rice and corn strains and separated by 1.7% sequence divergence, which does not support the existence of cryptic species. S . frugiperda larvae were also recorded on Sorghum bicolor (L.) Moench (10.6%), Solanum tuberosum L. (2.8%), Ipomoea batatas (L.) Lam. (1.9%), Saccharum officinarum L (0.8%), Phaseolus vulgaris L. (0.4%) and Gossypium hirsutum L. (1.9%). This study show that two strains are present in all agroecological zones in Cameroon, and probably in neighboring countries of central Africa sharing the same agroecologies. Management options should therefore consider the use of specific natural enemies and an informed decision of intervention based on strain capture and damage threshold, to avoid pesticide resistance that may arise from inadequate use of chemicals. Further studies should also be undertaken to assess the response of the two S . frugiperda strains to biopesticides and botanical insecticides.

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

“…In addition, as a pure leaf feeder, FAW larvae produced higher leaf damage and dispersal potential than stemborers. The devastating character in maize fields of FAW has been reported in several studies (Goergen et al, 2016; Srinivasan et al, 2018; Fotso Kuate et al, 2019).…”

“…It has also displaced Chilo orichalcociliellus Strand in the coastal region of Kenya (Ofomata et al, 1999) and may gain an advantage over B. fusca and S. calamistis in the utilization of maize (Mwalusepo et al, 2015; Ntiri et al, 2016). Recently, the fall armyworm (FAW), Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), invaded sub‐Saharan Africa, where it has seriously limited maize yields (Goergen et al, 2016; Cock et al, 2017; Fotso Kuate et al, 2019). Recent observations indicate that it closely interacts with maize stemborer communities (Sokame et al, 2020) and might also displace the stemborers.…”

Chromosome level draft genomes of the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), an alien invasive pest in China

“…Moreover, the FAW always hides inside the stem of maize, this makes the insecticide much less effective. Although many pesticides are less harmful to the environment and humans, all these factors can lead the sublethal effects, which possibly help the FAW to evolve resistance against the pesticides 25–27 . An effective compensating management for insecticides is the use of Bacillus thuringiensis (Bt) toxins produced by the by the bacterium.Bt plants have been proved fatal to many insect pests, including the FAW 28–30 .…”

“…Although some research reported the resistance of FAW to Bt maize 29,30 , multiple genes or new gene with more or new Bt toxin expressed are still thought to have a good performance for resisting the FAW 29,30 . Biological control, including the, introduction of natural enemies and using companion cropping system 19,21,25,31,32 , is also an effective way to resist the FAW.…”

Intensitas serangan Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae) pada pertanaman jagung di Kabupaten Garut dan Tasikmalaya, Jawa Barat

“…UGF adalah ngengat yang dapat bermigrasi dan bersifat polifag sehingga resiko penyebarannya sangat tinggi (Goergen et al 2016). Berasal dari wilayah tropis belahan barat Amerika Serikat dan Argentina, UGF kemudian menyebar ke wilayah Afrika dan akhirnya terdeteksi di Asia (Kuate et al 2019;Ma et al 2019). UGF juga dilaporkan sebagai hama utama pada beberapa tanaman kelompok Poaceae lainnya, seperti padi, tebu, gandum, dan sorgum (Yu et al 2003;Goergen et al 2016).…”