CARACTERISTIQUES DE L’EVOLUTION SPATIO-TEMPORELLE DE HELICOVERPA ARMIGERA HÜBNER (LEPIDOPTERA - NOCTUIDAE) DANS LES ZONES DE PRODUCTION COTONNIERE DE COTE D’IVOIRE : IMPACT DU PROGRAMME DE GESTION DE LA RESISTANCE AUX PYRETHRINOÏDES

In order to update knowledge on the spatio-temporal evolution of Helicoverpa armigera, the geographical areas and the seasons of predilection of adult and larval populations have been studied in the last six years from 2012 to 2017. Monitoring of natural adult populations in different locations has established that populations are more abundant in South cotton production areas compared to the north. The most important outbreaks occurred in two phases (August and Mid-October to Mid-November. The monitoring of larval populations carried out on farm scale showed that infestations started on cotton early August and increased in September and October, reflecting a strong relationship between the evolutions of adult populations, larval infestations and cotton phenology. Late sowings D5 and D6 exhibited higher levels of infestation (0.213 to 0.762 larvae/30 plants) as compared to early sowing (0.21-0.31 larvae/30 plants). Annual variations of pest infestation levels increased from years to years, fluctuating from 0.008 to 0.024 larvae/30 plants over the study period. Mapping of the geographic distribution of infestation showed more severe pest pressure in the North East and South East cotton areas particulary in mostly in surrounding areas of Niakara, Ouangolo, Nielle and Bouake (1.02 ; 0.86 ; 0.83 and 0.74 larvae/30 plants). With regard to the emerging status of H. armigera over recent years, the current pyrethroid resistance management strategy deserves to be improved on the basis of the pest geographic and seasonal profiles.