The fall armyworm, Spodoptera frugiperda, is an invasive lepidopteran pest capable of feeding on more than 80 crop species. Although maize is its principal economic host, infestations can also affect rice, sorghum, cotton, legumes and vegetable crops. Native to tropical and subtropical regions of the Americas, the species has expanded through Africa, Asia, Oceania and parts of Europe, creating a persistent challenge for crop protection and food security.
The pest is particularly difficult to manage because of its high reproductive capacity, migratory behaviour, broad host range and ability to develop resistance under repeated insecticide exposure. The larvae frequently feed deep inside the maize whorl, where they are partially protected from contact treatments. Excessive dependence on a limited number of synthetic insecticides may consequently reduce long-term control efficacy while increasing selection pressure for resistance. Integrated pest management, rather than exclusive reliance on one treatment, is therefore considered the most sustainable control framework.
Within this framework, researchers are increasingly evaluating plant-based biopesticides against Spodoptera frugiperda. These products include crude plant extracts, essential oils, isolated phytochemicals and nanoformulations designed to protect volatile or unstable active compounds. Recent laboratory studies have identified larvicidal, antifeedant, ovicidal and development-disrupting effects in extracts from neem, Piper, Tithonia, Simarouba, Humulus and several aromatic plants.
Nevertheless, promising laboratory toxicity should not be confused with proven agricultural performance. Many candidates have not yet been evaluated through replicated field trials, standardized manufacturing processes, residue studies or comprehensive assessments of their effects on natural enemies and other non-target organisms. Current evidence therefore supports continued development of botanical insecticides, but not the assumption that every plant extract is effective, safe or suitable for direct use by farmers.
Scientific Rationale for Botanical Fall Armyworm Control
Limitations of conventional insecticide-dependent management
Synthetic insecticides remain important for the rapid suppression of severe fall armyworm infestations. However, intensive and poorly coordinated applications can select resistant populations, particularly when products with the same mode of action are applied repeatedly. Fall armyworm populations have already demonstrated resistance to several conventional insecticide groups in different parts of the world.
Resistance is not the only concern. Broad-spectrum applications may expose parasitoids, predators and other organisms that contribute to natural pest regulation. Treatments can also be less effective when applications are poorly timed or when older larvae have moved into protected parts of the plant. These limitations have encouraged research into additional control agents that could diversify modes of action and reduce the number of conventional applications.
The objective of plant-based biopesticides against Spodoptera frugiperda should not necessarily be the complete elimination of synthetic insecticides. Their most realistic role may be to provide additional treatment options within integrated pest management programs combining pest surveillance, economic thresholds, cultural control, biological control and selective chemical interventions. FAO likewise promotes integrated management rather than dependence on a single control technology.
Biological activities of plant secondary metabolites
Plants produce diverse secondary metabolites that protect them against herbivores and pathogens. These compounds include terpenoids, phenolics, alkaloids, flavonoids, amides and glycosides. Depending on their chemical properties and concentration, they may repel insects, inhibit feeding, disrupt nervous-system enzymes, interfere with digestion or modify insect growth and reproduction.
Botanical extracts often contain several bioactive molecules rather than a single standardized active ingredient. This chemical complexity may create multiple biological effects, but it also complicates formulation and quality control. The composition of an extract can vary according to plant genotype, geographical origin, environmental conditions, harvested organ, maturity, extraction solvent and storage conditions.
A recent investigation of Piper retrofractum, for example, found that toxicity varied with both geographical origin and extraction solvent. Hexane extracts were more toxic to S. frugiperda than ethanol extracts in the reported experiments, demonstrating that a plant species name alone does not adequately define a botanical pesticide.
Research must therefore characterize botanical materials chemically as well as biologically. Without chemical fingerprints or quantified marker compounds, results obtained with one extract cannot necessarily be reproduced using plants collected in another region or prepared by another extraction method.
Recent Studies of Plant Extracts
Neem and other locally available pesticidal plants
Neem, Azadirachta indica, is one of the most extensively investigated pesticidal plants. Its limonoids, including azadirachtin-related compounds, can affect feeding, moulting and development in numerous insect species. However, the efficacy of neem products depends strongly on the plant material, extraction technique, active-compound concentration and application method.
A 2024 laboratory study compared ethanolic extracts of A. indica, Eucalyptus globulus, Parthenium hysterophorus, Cannabis sativa, Citrullus colocynthis and Nicotiana tabacum against third-instar fall armyworm larvae. After 72 hours, neem produced the lowest median lethal concentration among the botanical extracts, with an LC₅₀ of 186.104 ppm. At 400 ppm, neem caused approximately 64% mortality. Tobacco was the least active of the tested extracts, with an LC₅₀ of 720.980 ppm.
These findings support neem as a candidate botanical insecticide, but they also illustrate an important limitation. Even the best-performing treatment did not consistently produce complete mortality under the reported conditions. Botanical control should therefore be evaluated through several endpoints, including reduced feeding, delayed development and impaired reproduction, rather than through acute mortality alone.
The results also cannot be transferred directly to homemade aqueous neem preparations. The study used ethanolic extracts prepared under controlled conditions. Water-based farmer preparations may extract different compounds at different concentrations, and their stability may vary considerably.
Piper, Tithonia, Annona and other botanical candidates
A 2025 study evaluated extracts of spiked pepper, Piper aduncum; African marigold, Tagetes erecta; Mexican sunflower, Tithonia diversifolia; sugar apple, Annona squamosa; and soursop, Annona muricata. The researchers measured larval toxicity, feeding inhibition and egg-hatching suppression rather than relying on a single biological endpoint.
Among the five extracts, P. aduncum was the most toxic, with reported LC₅₀ and LC₉₅ values of 0.11% and 0.70%, respectively. T. diversifolia produced the strongest antifeedant activity. At the higher ovicidal concentration, all five extracts inhibited egg development by more than 75%, with P. aduncum producing the highest inhibition.
This study demonstrates that plant extracts may have different functional profiles. The most lethal extract is not necessarily the strongest feeding deterrent, while a relatively weak larvicide could still contribute to population management by reducing egg hatch or larval consumption. Screening programs should consequently include mortality, consumption, development, fecundity and egg viability.
However, LC₅₀ values from different publications should not be compared as though they were generated under identical conditions. Studies may use different larval instars, solvents, exposure times, leaf-dipping procedures, topical applications or artificial diets. Potency comparisons are scientifically valid only when materials are tested under the same experimental protocol.
Metabolomic investigation of Simarouba glauca
A 2025 Scientific Reports study used untargeted metabolomics to examine extracts from the bark, leaves and seeds of Simarouba glauca. Different solvents produced markedly different extraction yields and biological activities. The ethyl acetate bark extract showed the greatest toxicity, with a reported LC₅₀ of 4.80%, while cold-pressed seed oil produced more than 52.3% feeding inhibition at the higher concentrations.
Chemical analysis identified several metabolites associated with the plant fractions, including gamma-sitosterol, lanosta-8,24-dien-3-one and fatty-acid derivatives. Multivariate analysis separated the bark fractions from the leaf and seed samples, confirming that the different plant organs had distinct chemical profiles.
This metabolomics approach represents an important development in research on plant-based biopesticides against Spodoptera frugiperda. Instead of reporting only that an extract is toxic, researchers can begin identifying the metabolites correlated with activity. Nevertheless, a statistical association between a metabolite and an active fraction does not prove that the compound is independently responsible for toxicity. Isolation, bioassay-guided fractionation and mechanistic testing are still required.
Essential Oils and Isolated Active Compounds
Essential oils as larvicidal and antifeedant agents
Essential oils contain volatile compounds such as monoterpenes, sesquiterpenes and phenylpropanoids. Several recent studies have reported mortality and feeding inhibition in fall armyworm larvae exposed to oils from mint, citrus, lemongrass, eucalyptus, Piper and other aromatic plants.
Their volatility can be both an advantage and a limitation. Volatile constituents may act rapidly through contact or fumigant exposure, but they can also evaporate or degrade under sunlight, oxygen and elevated temperatures. Many essential oils also have poor water solubility, making uniform field application difficult without emulsifiers or encapsulation systems.
Chemical characterization is essential because oils sold under the same botanical name may contain different chemotypes. The concentration of major compounds can change according to growing conditions, plant developmental stage and distillation procedure. Consequently, biological activity should be linked to gas chromatography–mass spectrometry profiles wherever possible.
Identification of insecticidal monoamides from Humulus scandens
A 2025 study moved beyond crude-extract screening by isolating two monoamide compounds from the ethyl acetate extract of Humulus scandens: N-p-coumaroyl tyramine and N-trans-feruloyl tyramine. Both compounds produced dose-dependent contact and dietary toxicity against fall armyworm, although N-trans-feruloyl tyramine was the more active molecule.
The stronger compound had a reported contact LC₅₀ of 47.97 μg/mL. Enzyme experiments indicated that both monoamides inhibited fall armyworm acetylcholinesterase as reversible competitive inhibitors. N-trans-feruloyl tyramine produced an IC₅₀ of 19.71 ± 1.98 μg/mL, while the estimated inhibition constants were 23.76 and 20.79 μg/mL for the two compounds.
This type of mechanistic research is important because it connects observed toxicity with a specific biochemical target. It may facilitate the development of standardized active ingredients and enable comparisons with existing insecticide modes of action.
The work nevertheless remains an early-stage laboratory investigation. The environmental persistence, crop compatibility, mammalian toxicology and effects of the isolated monoamides on beneficial insects have not yet been established comprehensively. Their potential as agricultural products therefore remains scientifically plausible but commercially unproven.
Nanoformulations of Plant-Based Biopesticides
Nanoencapsulation of lemongrass essential oil
Nanoencapsulation is being investigated as a method for improving the stability, dispersion and biological efficacy of essential oils. A 2025 study encapsulated lemongrass oil using beta-cyclodextrin and gum arabic. Gas chromatography–mass spectrometry identified D-limonene, E-citral and Z-citral as the principal constituents of the tested oil.
The resulting capsules ranged from approximately 280 to 472 nanometres, with encapsulation efficiencies between 51.94% and 83.59%. After 96 hours, the nanoencapsulated treatment had an LC₅₀ of 1.52%, compared with 2.48% for unencapsulated lemongrass oil. The formulation also adversely affected survival, development and population-growth parameters measured using a two-sex life-table approach.
These findings suggest that encapsulation increased the apparent biological efficacy of the oil under laboratory conditions. A lower LC₅₀ may result from improved dispersion, protection from degradation or more sustained release of active compounds. Field persistence and rainfastness, however, were not established by the laboratory bioassay.
Piper auritum nanoemulsions and other nanocarriers
A 2026 study compared three formulations containing Piper auritum essential oil with approximately 70% safrole: a nanoemulsion, a microemulsion and a silver-nanoparticle formulation. Droplet sizes ranged from 19 to 48 nanometres. Among the tested products, the nanoemulsion showed the greatest larvicidal activity, with an LD₅₀ of 0.97 µg/cm² against second-instar larvae. It was reported to be approximately ten times more active than the other formulations in the experimental system.
The treatments also produced morphological damage in larvae and pupae and deformities in surviving adults. Stability tests over 60 days detected remaining oxidized sesquiterpenes and phenylpropanoids, providing preliminary information about the chemical evolution of the formulations during storage.
Nanotechnology may therefore address some of the physical limitations of essential oils. Nevertheless, a nanoformulation should not automatically be described as environmentally safe because its active ingredient originates from a plant. Surfactants, carrier polymers and inorganic nanoparticles may each contribute to biological effects.
Silver-nanoparticle formulations require particularly careful examination because the environmental fate and non-target effects of the metal component may differ from those of the essential oil. Future research should distinguish the toxicity of the botanical active substance from that of the carrier system and formulation additives.
From Laboratory Bioassays to Integrated Pest Management
Standardization, safety and field performance
The latest studies provide strong evidence that numerous botanical materials can affect fall armyworm biology. However, the transition from laboratory activity to a registered agricultural product requires several additional stages. These include botanical authentication, chemical standardization, formulation optimization, storage testing, crop-safety evaluation, field efficacy trials and toxicological assessment.
The 2025 review of botanical extracts against fall armyworm identified many potentially active plant species but emphasized the importance of field evaluation and product development. Much of the published literature remains based on controlled laboratory assays rather than multi-location agricultural experiments.
Field conditions introduce ultraviolet radiation, rainfall, variable temperature, plant growth, uneven spray coverage and repeated pest immigration. A formulation producing high mortality on treated leaf discs may therefore perform differently when sprayed onto maize plants under tropical conditions.
Non-target safety also requires direct investigation. Plant-derived compounds evolved partly as chemical defences and may be biologically active against organisms other than the target pest. Environmental safety cannot be inferred solely from rapid degradation or natural origin.
Practical role of botanical products in fall armyworm management
The most credible near-term application of plant-based biopesticides against Spodoptera frugiperda is as one component of diversified pest management. Botanical products could potentially be used during early infestations, alternated with products having different modes of action or integrated with microbial insecticides and conservation biological control.
Such integration could reduce selection pressure associated with repeated use of the same conventional insecticide. It could also create locally accessible control options where suitable pesticidal plants are abundant. However, the use of locally collected plants raises questions about dosage consistency, correct species identification, extraction safety and conservation of plant resources.
Commercial formulations offer better opportunities for standardization than improvised preparations, but they must remain affordable and practical for farmers. Cost-effectiveness should be assessed through crop yield and treatment costs rather than larval mortality alone.
Agronomic recommendations should ultimately be based on pest density, crop growth stage and expected economic damage. Preventive application of poorly characterized botanicals is not automatically more sustainable than evidence-based application of a selective registered insecticide.
Conclusion
Recent research has significantly expanded the scientific basis for plant-based biopesticides against Spodoptera frugiperda. Neem, Piper aduncum, Tithonia diversifolia, Simarouba glauca, Humulus scandens and several essential-oil-producing plants have demonstrated larvicidal, antifeedant, ovicidal or development-disrupting effects.
Studies published between 2024 and 2026 also show a transition from simple plant-extract screening toward chemical characterization, metabolomics, isolation of active compounds and nanotechnology-based delivery systems. Nanoencapsulation of lemongrass oil increased laboratory toxicity, while a Piper auritum nanoemulsion produced stronger larvicidal activity than the alternative formulations tested.
Despite this progress, the scientific literature does not yet establish a universally effective botanical replacement for conventional fall armyworm insecticides. Most candidates remain at the laboratory or early formulation-development stage. Direct comparisons among studies are restricted by differences in extraction procedures, concentrations, larval stages and exposure methods.
The future of plant-based fall armyworm control will depend on reproducible chemical composition, realistic field testing, non-target safety assessments and affordable formulation technology. Botanical insecticides are therefore best understood not as simple natural substitutes, but as technically complex tools that may strengthen integrated pest management when supported by rigorous scientific validation.
Selected Scientific References
Bhosle, D., Srinivasan, T., Elaiyabharathi, T., Shanmugam, P. S., et al. “A review on use of botanical extracts for the management of fall armyworm Spodoptera frugiperda.” Journal of Plant Diseases and Protection, 132, 17, 2025.
Liu, Y., Wu, X., Li, F., Qin, D., Gao, X., Wu, G. and Qin, X. “Insecticidal activity of monoamide compounds from Humulus scandens against Spodoptera frugiperda.” Frontiers in Plant Science, 16, 2025.
Siregar, H. M., Dadang, Sartiami, D. and Winasa, I. W. “Evaluation of plant extracts as botanical insecticides for controlling Spodoptera frugiperda.” Journal of Applied and Natural Science, 17, 2025.
“Determination of insecticidal potential of selected plant extracts against fall armyworm larvae.” Heliyon, 2024.
“Insecticidal effects of nano-encapsulated lemongrass essential oil on the population parameters of Spodoptera frugiperda using two-sex life table.” Scientific Reports, 2025.
“Untargeted metabolomics-based study of extracts from Simarouba glauca plant parts for insecticidal effects against Spodoptera frugiperda.” Scientific Reports, 2025.
“Nanoformulations of the Piper auritum essential oil for the control of Spodoptera frugiperda.” Agriculture, 16, 308, 2026.
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