Effect of Temperature and Rainfall on the Proliferation of Cocoa Mirids in the Yamoussoukro District in Central Côte d’Ivoire

Abstract

Mirids are a major concern for cocoa producers in Côte d’Ivoire. These biting and sucking insects feed on pods, buds and orthotropic branches. They cause 30% of crop losses per year. This study was carried out to determine the different species of mirids and their outbreak periods in the Yamoussoukro district of Côte d’Ivoire. Mirid outbreaks were assessed by sampling twice a month using the tarpaulin technique. Cocoa trees containing mirids or mirid outbreaks that were identified and covered were treated with a high dose of registered insecticide with the active ingredient acetamiprid and bifenthrin. Mirids killed by the spray were counted on the tarps 5 hours after treatment. Rainfall and temperature data were also collected in the study areas. The results revealed the presence of 3 species of mirids in Yamoussoukro district: Sahlbergella singularis , Distantiella theobromae and Helopeltis sp. Sahlbergella singularis , with a rate of 99.82% of the mirids counted was the main species in the area. The curve revealed a period of high mirid outbreaks in the district. This period extends from May to March with a population peak in August or September depending on the year. The outbreak of mirids in the district starts during rainy periods and gradually stops with dry periods. Also, the periods of high mirid outbreaks in the district seem to coincide with low temperatures of the year. However, the Spearman correlation test at the 5% threshold showed that there is no significant correlation between mirid outbreaks and the climatic parameters of temperature and rainfall.