Effects of Rainfall Variability on the Occurrence of Crop Pests at Foumbot Subdivision, West Region of Cameroon

Rainfall is an essential climate variable for plant development. Its variability has an impact on the plant phenology. The present study aimed to analyze the variation in rainfall in order to determine the rainfall hazard responsible to the occurrence of pest and diseases in tomato and maize. The study was carried out at Foumbot located in the Western Region of Cameroon, more specifically in the Noun Division. Part of this district occupies the left bank of the river Noun, more precisely the Noun plain. The rainfall data was collected from the period of 1997 to 2019 and analyzed. Monthly data was collected from 1997 to 2019 and daily data from 2010 to 2019.The surveys were made with three groups of actors: the agricultural services (the Agricultural Delegation of Foumbot), the agricultural research services (IRAD of Foumbot), and the farmers' organizations (the Common Initiative Group (CIG) and cooperatives). Stratified random sampling was used for the surveys. The results revealed that the first cropping season from March to July is characterized by an increase in consecutive dry days of 5 to more than 7 days. This situation has been confirmed by 30% of the investigated actors, who mentioned that consecutive days without rain were favorable to the appearances of pest and diseases. The SPI (Standard Precipitation Index) analysis of rainfall data showed that this can be link to the prolongation of the dryness season in the cropping season which started in March. Therefore, the monthly SPI consider March as a dry month. So, March and May are not suitable for the beginning of cropping season due to the multiplication of drought episode. The tomato leaf miner (Tuta absoluta) and the armyworm had been identified as the pest and disease which appear during the consecutive dry days. They are characterized by an increase in temperature. The study is useful for agricultural drought management and crop productivity in an unpredictable environment.