An invasive species recently introduced to Madagascar and Réunion, the fall armyworm (FAW) Spodoptera frugiperda causes significant damage to maize crops. Biosolutions such as co-products from essential oil distillation could provide promising and sustainable alternatives to synthetic pesticides, in a circular economy perspective. We evaluated the potential of liquid residues (hydrosols) from the distillation of aromatic plants, in tests on maize leaf disks in Petri dishes, under artificial infestation by neonate FAW larvae (3 per leaf disk for 24h). We assessed, on the one hand, in both Madagascar and Réunion, 0.4% essential oil solutions produced in the Highlands of Madagascar, and on the other hand, solely in Madagascar, 10% and 30% solutions of floral waters from several Malagasy sources. The essential oils evaluated were lemon eucalyptus, geranium, citronella, rosemary, and camphor. The hydrosols were those of geranium, citronella, and clove. The tests highlighted higher larval mortality and lesser leaf damage with the essential oils of citronella, lemon eucalyptus, and geranium, while the essential oil of camphor (“Ravintsara”) had no effect. The tests with hydrosols established citronella as the most promising in terms of effects on larval mortality and on reduction of leaf damage. These tests will be complemented by the evaluation of the essential oil of lemon eucalyptus and the characterization of molecules and mechanisms of action (biocidal, repellent, and/or antifeedant) involved. We will also examine the effect of incorporating the solid residues from essential oil distillation into the soil on maize growth and reaction to FAW attacks. Finally, these results will be confirmed in a field trial with leaf spraying of essential oil solutions, under natural FAW infestation.