Article Spatial Distribution and Genetic Diversity of The Fall Armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae) in the Bali Province and Lesser Sunda, Indonesia I Wayan Supartha 1,* , I Wayan Susila 1 , I Kadek Wisma Yudha 2 , I Wayan Eka Karya Utama 2 , I Wayan Sandi- kayasa 3 , I Putu Mahendra Putra Gautama 3 , Sri Wahyuni 4 , and Putu Angga Wiradana 5 1 Laboratory of Integrated Pest Management (IPMLab), Faculty of Agriculture, Udayana University, Jln. PB. Sudirman, Denparas City (80234) 1; yansupartha@yahoo.com 2 Doctoral Program of Agriculture Science, Faculty of Agriculture, Udayana University, Jln. PB. Sudirman, Denpasar City (80234) 2; wismayudha@gmail.com 3 Graduate Program of Biotechnology of Agriculture, Faculty of Agriculture, Udayana University, Jln. PB. Sudirman, Denpasar City (80234) 3; sandikaysa6@gmail.com 4 Faculty of Agriculture, Flores University, Ende, Nusa Tenggara Timur, Indonesia 5 Study Program of Biology, Faculty of Health, Science and Technology, Universitas Dhyana Pura, North Kuta, Badung Regency (80361), Bali Province, Indonesia 5 ; angga.wiradana@undhirabali.ac.id * Correspondence: yansupartha@yahoo.com ; Tel.: - Abstract: Spodoptera frugiperda is an invasive pest that has spread in various parts of the world. These pests have the ability to spread and adapt highly to new habitats. Until now, it is not known with certainty the distribution of these invasive pests in Eastern Indonesia, especially Bali and Nusa Tenggara. This study aims to map the spatial distribution and genetic distribution of S. frugiperda which damages maize in the areas of Bali and Nusa Tenggara. This research was conducted using a survey method from May to September 2022 covering the islands of Bali, Lombok, Sumbawa, Sumba, Flores, and Timor. The results showed that S. frugiperda had spread evenly in Bali and Nusa Tenggara. The results of PCR amplification in the COI gene from 9 sample isolates from all research locations showed the similarity of DNA bands leading to the Spodoptera frugiperda species with a banding pattern length of 683 – 697. These results indicated that the distribution of genetic variants of corn caterpillars in Bali, NTB, and NTT was confirmed as S. frugiperda species. However, the isolated gene S. frugiferda, which was shown by the alignment results of the sequences from Lom- bok, was confirmed as a different strain from strains from Bali, Sumba, Sumbawa, Flores, and Timor. This incident can be seen from the difference in the protein base composition of S. frugiperda from Bali, Sumba, Sumbawa, Timor, and Flores. The results of phylogenetic analysis in this study con- firmed 3 clusters of the genetic closeness of S. frugiperda. Cluster-1 comes from the results of the search for specimens of JB FAW and KB FAW from Bali, SB FAW and SB FAW Sorghum from Sumba, SW FAW from Sumbawa, KP FAW from Timor, and FL FAW from Flores. Cluster-2 is an isolate outside of our species. Cluster-3 comes from the search for LT and LS FAW specimens from Lombok. The genetic distance between cluster-1 and cluster-3 is quite far, which is 0.20 mu. Keywords: The Fall Armyworm, Spodoptera frugiperda, invasive species, mapping distribution, DNA-barcoding 1. Introduction The Fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae) is one of the invasive pests and is responsible for decreasing crop yields and causing economic losses in the agricultural sector in the world [1]. These pests damage agricultural crops such as corn, rice, sorghum, wheat, barley, buckwheat, oats, ryegrass, soybeans, tobacco, tomatoes, potatoes, peanuts, cotton, sugar beets, alfalfa, and onions and more than 300 other plant species [2]. As a well-known pest, FAW can produce yield losses ranging from Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 4 October 2022 doi:10.20944/preprints202210.0020.v1 © 2022 by the author(s). Distributed under a Creative Commons CC BY license.