In Côte d'Ivoire, the stem borer, Apate terebrans, is one of the three main insect pests of cashew (Anacardium occidentale), an important cash crop. But, the lack of scientific knowledge about its ecology is a real obstacle to the development of efficient control methods. This study aimed to know the seasonal fluctuation of A. terebrans, in relation to the phenological stage of cashew and some climatic factors. The cryptic life of the pest led to the evaluation of its abundance by counting monthly the openings of fresh galleries that it digs in the cashew tree. Systematic sampling was carried out on 1924 cashew trees distributed in 10 orchards in the departments of Bondoukou and Bouna in the North-East of Côte d'Ivoire, from July 2018 to June 2020. Climatic data were recorded over this period. The first individuals of A. terebrans were observed in July in the rainy season; peak numbers were reached in November-December in the dry season, before decreasing considerably in January and becoming nil in March-April. Individuals were significantly more abundant at cashew flowering. Significant differences were observed between the abundances within and between departments and from year to year. Simple regression analyses showed that temperature favours the growth of pest populations, while rainfall and hygrometry are unfavourable. This study contributes to the effective control of A. terebrans, and provides insights into the determinants of the variability of A. terebrans infestations from one orchard to another.