The fall armyworm (FAW) Spodoptera frugiperda J.E Smith poses a serious threat to cereal production in general and corn production in particular. It causes enormous damage and significant yield losses in Niger. To counter this damage, farmers are increasingly using synthetic pesticides despite their toxicity to humans and the environment. There is therefore an urgent need to find an alternative to this chemical control method, this is why a study on the biological effectiveness of biopesticides on FAW larvae was conducted during the cold dry season of 2023 and the wet season of 2024 in Kalapaté in the Birni department. The design was a completely randomized block with four replicates. The insecticide treatments were as follows: Emacot, Bocia senegalensis, Jatropha curcas, and Eucalyptus sp, 250 g of each fresh leaf/5 L of water), Neem (Azadirachta indica) grain powder 125g/2.5l of water and a negative control that was treated with plain water, i.e., 4L of water. The results shows that the severity rate was higher in the dry season (85%) than in the wet season (18%). The damage was more severe in the negative control than in the treated ones. In both seasons, the application of Emacot reduced the damage to corn plants, followed by Neem. These results reveal that aqueous neem seed extract (125 g/5 L of water) can be applied alternatively to the chemical insecticide against S. frugiperda in Niger in the presence and absence of rainfall.