In Niger, millet and sorghum are the main cereals produced and consumed by the majority of the population. Maize and wheat have an important place in production systems and represent a real basis for food security [1] . Despite the importance of cultivated cereals, they have been experiencing difficulties for several decades. Erratic rainfall and the appearance of pests generate and aggravate a set of unfavorable factors such as soil impoverishment, stagnation or even a decline in agricultural production at a time when population growth is increasingly high [2] . It is in this context that the new pest called Fall armyworm (Spodoptera frugiperda) was reported in Niger in 2016 and 2 years after its appearance, this caterpillar has invaded the entire national territory [3] . Surveys conducted in these areas have shown that it is present in a number of crops, including maize, sorghum, millet, onions, cabbage and okra.

The Fall armyworm (Spodoptera frugiperda) is an insect pest that attacks more than 350 plants, causing damage to cereal crops such as maize and sorghum as well as to vegetable crops [4] - [6] . This caterpillar attacked millet in Torodi, but also in Maradi during the rainy season (several thousand hectares). It is therefore a real danger for cereal crops and it is necessary to know it in order to be able to fight against it [7] .

The caterpillar has caused significant damage to maize crops throughout almost the entire national territory. However, the fear that hangs over experts today is that this highly polyphagous insect (which feeds on several plants) will attack key cereals such as millet and sorghum. It has already been known for a long time that some of the species of the same genus, namely Spodoptera exempta and Spodoptera littoralis, attack the crops of millet and sorghum, the main cereals consumed by rural Nigerien households [8] . It is true that this butterfly has excellent flight abilities, but the spread of infestations is also favored by transboundary transport from one country to another [8] .

Fall armyworms appear to be much more damaging to maize in West and Central Africa than most other Spodoptera species in Africa [9] [10] .

Indeed, pests are a major constraint in maintaining and improving the productivity of agricultural plots around the world. Their control is, to date, based on chemical control, which would have harmful consequences on the environment. To remedy this, several authors recommend the use of an integrated pest management approach [11] - [13] . This is the case for the management of the Fall armyworm (Spodoptera frugiperda) [13] . This caterpillar is particularly fond of cereals, including maize, sorghum and millet.

The need to study Fall armyworm in Niger is imperative because of its devastating effects on essential crops. The large-scale damage caused underlines the urgency of understanding its feeding behaviour, its ecology and its life cycle in order to identify effective control methods. In addition, the potential threat of this caterpillar to key cereals such as millet and sorghum requires special attention, as these crops are fundamental to Nigerien rural households.

There is therefore a need to further explore methods of controlling this pest to better protect already vulnerable smallholder farms.

The study was carried out on the experimental site of the Faculty of Agronomy of the Abdou Moumouni University of Niamey, itself located in Niamey District V on the right bank of the Niger River. The geographical coordinates of this experimental site are 13˚30'0" north latitude and 2˚5'35" east longitude. Figure 1 gives us the graphic transcription of this location.

The climate is Sahelian, characterized by low rainfall, poorly distributed in time and space, and high temperatures (with an average of 45˚C in April).

The soil is of the leached tropical ferruginous type with a sandy-clay texture. The soil is progressively enriched in organic and mineral matter, thanks to organic and mineral fertilizers and previous cultivation.

Vegetation is average, with woody species poorly distributed in space. The species encountered are: Ferdherbia albida, Balanites aegyptiaca, Prosopis julifora, Calotropis procera and Acacia senegalensis.

The trapping device installed at the experimental site made it possible during the winter season to capture one hundred and forty Spodoptera frugiperda, so the 1st hypothesis is verified. This follow-up lasted thirteen weeks and involved four fields in the Faculty of Agronomy of the Abdou Moumouni University of Niamey. The highest number of trapped species was obtained in the week of 16.10.2023 with a peak of thirty-one male S. frugiperda captured in the traps after crop harvest. Our results do not corroborate those found by [16] , who showed that the capture rate decreases at the end of the winter season. In the present study, more male Spodoptera frugiperda were observed in field 3 with an average of 5.615 individuals, which is less attacked than in field 4 with an average of 0.769 individuals, which is more attacked. The results obtained show that there is no significant difference in the infestation rate between crops, hypothesis 2 is verified. These results are contrary to those found by [17] who showed that the infestation rate of maize, sorghum and millet is 78.32%, 3.31% and 1.75%, respectively. The results of this study showed that the number of plants attacked in field 4 (maize) is greater than in field 1 (maize and sorghum) followed by field 3 (sorghum) and then field 2 (millet), but the analysis of variance showed that there is no statistical difference in the number of plants attacked by the caterpillar depending on the field. During our observations, the maize in field 4, which is intercropped, is more attacked than the maize in field 1, which is in pure cultivation, and no attack on maize, which is intercropped with okra and sorrel in field 3. These results are contrary to those found by [15] who showed that in pure culture. Fall armyworm attacked leaves, stems, panicles and spikes. But the damage is greater at the flowering and heading stage. These results corroborate those of [18] who showed that the highest average attack rates were observed for the 3 varieties at flowering before stabilizing at heading. This could be explained by the fact that the caterpillars of S. frugiperda have a wide variety of food (leaf, stem and panicle) at their disposal, and also corroborate those of [19] who showed that Fall armyworm causes more damage at the flowering stage. [7] has shown that all ears can be attacked, thus causing a very significant loss of production, and the extent of the damage is due to the insect’s spectacular reproductive capacity. [8] has shown that Fall armyworm mainly eats maize leaves. Occasionally, it also attacks the ears. Generally, these ears are not eaten by humans. While direct damage from S. frugiperda does not affect the safety of maize, it may make it more conducive to the presence of aflatoxin. In addition, the results obtained in our experiment show that Fall armyworm attacks maize more than sorghum and millet. These results confirm those of the [7] , which showed that S. frugiperda causes damage to cultivated cereals such as maize and sorghum. The damage to maize is severe, even very severe. This is sufficient evidence that the caterpillar of this butterfly, called the “Fall armyworm”, has a particularly devastating impact [15] . [14] showed that due to its spread and distinctive ability to cause damage to multiple crops (this speed is thought to be due to the armyworm’s ability to attack a very diverse range of species, especially grasses).

This study monitored and assessed the damage caused by the Fall armyworm, Spodoptera frugiperda, to maize, sorghum and millet crops. The results showed that Spodoptera frugiperda is present on the site where these three crops (maize, sorghum and millet) are grown. The number of Spodoptera frugiperda captured was highest in field 3. Weekly monitoring of the S. frugiperda population in the fields showed that there were three generations on the experimental site. The results of the incidence assessment showed that there was no significant difference between the fields. The number of plants attacked in field 4 (maize) was greater than in the other fields, but analysis of variance showed that there was no statistical difference in the number of plants attacked by the caterpillar depending on the field. The results of the in vitro consumption test showed that the armyworm consumed more corn leaves. Farming conditions were not optimal for the complete cycle of Spodoptera frugiperda. This study shows that the armyworm causes damage to maize, sorghum and millet under our experimental conditions. The study concludes that while FAW poses a threat to cereal production, the observed damage levels are not alarming, possibly due to pesticide use by farmers and natural enemies.