| dc.description.abstract | Maize (Zea mays L.) is a strategic commodity for the food, feed, and bioindustry sectors in Indonesia. The invasion of fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), has increased pest pressure in maize production systems and may reduce productivity. In many regions, FAW control still relies heavily on synthetic insecticides, which can trigger resistance, resurgence, and increase residue risks. Therefore, more specific yet sustainable control approaches are needed. Sex pheromones are one of the most appropriate alternatives; however, their development requires strong local evidence because the composition and ratio of FAW sex pheromones may vary according to genetic background and geographic region.
This study aimed to build an integrated scientific basis for developing sex pheromone formulations based on the characterization of FAW populations in Indonesia through several stages: (i) measuring the percentage of attacked maize plants and damage intensity, and characterizing populations using the mitochondrial markers cytochrome c oxidase subunit I (COI) and cytochrome c oxidase subunit II (COII), and the nuclear gene triose phosphate isomerase (Tpi); (ii) analyzing population identity and structure based on whole-genome sequencing (WGS); (iii) observing various parameters related to mating behavior; (iv) quantifying pheromone components using gas chromatography–flame ionization detection (GC–FID) to determine the local pheromone blend ratio of Indonesian populations; and (v) preparing synthetic pheromone formulations based on the local pheromone blend, followed by laboratory testing and field evaluation.
Field surveys were conducted at 21 maize-growing locations in Banten, West Java, and Central Java Provinces. The results showed that the percentage of FAW attack varied widely, ranging from 11 to 94%. Meanwhile, damage intensity was generally within the range of 25–50%, corresponding to the moderate damage category, with three locations showing severe damage, namely Kuningan, Pemalang, and Brebes. These findings emphasize the importance of sex pheromone-based monitoring systems to provide early-warning signals for potential FAW population outbreaks under uneven attack distribution.
Population identity was analyzed using COI, COII, and Tpi from 41 FAW populations across Java, Sumatra, Sulawesi, and Nusa Tenggara. The analysis showed low haplotype and nucleotide diversity, consistent with the characteristics of invasive populations. However, discordance was detected between the mitochondrial markers and Tpi. Diagnostic single-nucleotide polymorphism (SNP) in Tpi showed that all analyzed individuals were aligned with the corn strain, whereas the mitochondrial markers still showed rice-strain signals in Indonesian FAW populations.
WGS-based genomic analysis of 19 FAW populations from Java, Sumatra, Sulawesi, and Nusa Tenggara strengthened the inference that Indonesian FAW populations are strongly aligned with the corn strain and belong to an invasive cluster that is genetically close to populations from Africa and India. In addition, WGS analysis also revealed signals of local differentiation in certain genomic regions, particularly on chromosome 25.
Mating behavior observations were conducted on 9 FAW populations from Lampung and East Java Provinces. The results showed that dominant copulation activity occurred in the early dark phase or scotophase, especially 3–6 h after the onset of scotophase. This period was established as the operational window for pheromone-gland sampling in female FAW. In addition to copulation timing, this study recorded other mating behavior parameters, including copulation success of 53.05%, copulation frequency of 0–3 times per pair, precopulatory period of 1.30–2.78 days, copulation duration of 1.20–2.05 h, and male and female age at copulation, averaging 1.9 and 2.4 days, respectively. This information is important as a basis for understanding the reproductive behavior of FAW as an invasive pest in Indonesia.
The chemical basis of FAW sex pheromones in Indonesian populations was established from 9 populations originating from Lampung, West Java, and East Java Provinces. Pheromone gland extracts from unmated female adults (virgin) were analyzed using GC–FID for three main acetate components, namely (Z)-7-dodecenyl acetate (Z7–12:OAc), (Z)-9-tetradecenyl acetate (Z9–14:OAc), and (Z)-11-hexadecenyl acetate (Z11–16:OAc). The analysis showed that total pheromone amount varied according to female age and timing within the scotophase. To ensure comparability across populations, the reference extraction window was established using 3-day-old virgin females sampled at the 5th hour of scotophase. The main finding of this study was the establishment of a local pheromone blend reference for FAW sex pheromones in Indonesian populations with a ratio of 80:16:4 (Z9–14:OAc:Z11–16:OAc:Z7–12:OAc).
Candidate synthetic blends were then designed based on the local pheromone reference and prepared as formulations for laboratory and field testing. Wind tunnel and field evaluations showed that male FAW moths responded to several candidate pheromone formulations, with the most stable cross-season performance shown by formulation C (80:15:5). This result positions formulation C as a relevant operational starting blend for further development as a pheromone lure for FAW monitoring and control in Indonesia.
Overall, this study establishes an Indonesia-specific translational pipeline for FAW pheromone development by integrating field attack ecology, sequence-based genetic characterization, genome-wide population analysis, nocturnal reproductive behavior, and pheromone chemistry. This framework links invasion biology, strain interpretation, behavioral standardization, local pheromone profiling, and candidate blend evaluation to support pheromone-based monitoring and future mass trapping strategies within integrated pest management programs for maize in Indonesia. | |
