Population dynamics of Hypothenemus hampei (Ferrari) according to the phenology of Coffea arabica L. in equatorial conditions of North Sumatra

In the Toba Highlands of North Sumatra (Indonesia), coffee production (Coffea arabica L. var. Sigarar Utang) is an important outcome for smallholders; however, the attack of the coffee berry borer (CBB) Hypothenemus hampei, is an obstacle for the development of coffee cultivation in this area. This pest causes great economic losses produced by the development of its offspring inside the coffee berries, making it difficult to control. This concerning situation has led us to consider the development of a CBB control strategy, but beforehand, it was necessary to acquire key information on the phenology of the coffee tree and its implication on the bioecology of the pest. Thus, two study designs were set up, one comprising six plots with two different age classes and the other corresponding to a single plot dedicated only to the study of short distance dispersal of CBB. Part of this study focused on the phenology of the coffee trees and showed that berry production mainly takes place in the upper parts of the trees and significantly decreases with tree age. Due to the equatorial climate, berries were practically always present. Berries were produced following two major flowering periods and some minor ones distributed over the year, and harvested at regular intervals. Berry distribution on the branches varied over time. Dynamics of infestations by CBB showed that ripe berries were more infested than unripe berries because they had been exposed longer to CBB attacks, that older trees were more exposed than younger trees and that infestation was evenly distributed along branches. In addition, internode pedestrian dispersal of CBBs was shown to occur, but considerably less frequently than airborne dispersal. In conclusion, it appears that in the agro-climatic context of the Toba region, the virtual year-round presence of berries - which fosters CBB infestations and CBB short-distance dispersal - is a constraint that must be taken into consideration for designing future pest management measures. To this end, it will be necessary in particular to evaluate the potential of trapping mainly used in tropical areas and to put into practice the sanitation harvesting applied in other countries.