Where to sample? Ecological implications of sampling strata in determining abundance and impact of natural enemies of the coffee berry borer, Hypothenemus hampei

Several parasitoids of African origin have been introduced to coffee producing areas of the Americas and Asia as biological control agents of the coffee berry borer (CBB) Hypothenemus hampei (Coleoptera: Curculionidae). These parasitoids have become established in the field but their effect on the CBB has been limited. A two-year field study in Western Kenya has found Prorops nasuta (Hymenoptera: Bethylidae) to be the predominant parasitoid emerging from CBB-infested coffee berries collected on coffee trees or from the ground. P. nasuta comprises more than 75% of the total natural enemies collected. The density of P. nasuta was 90% higher in the berries collected from the ground than from the trees. Its hyperparasitoid, Aphanogmus sp. (Hymenoptera: Ceraphronidae), also emerged from both type of berries. Across the two seasons, the average P. nasuta density per berry was 18–35 times higher than that of Aphanogmus sp. Throughout the two years sampled, significantly higher numbers of P. nasuta and Aphanogmus sp. occurred between February and March, which coincides with the beginning of the rainy season. Higher numbers of live CBB females were recorded in berries collected from the trees. Nevertheless, mortality of adult CBB was considerably higher from January to March and started to decrease from April onwards. The possibly negative effects of cultural control practices in Latin America which include the removal of berries fallen to the ground on biological control of CBB are discussed, and the use of screened collection devices for these berries which would permit the release of parasitoids but prevent escape of the pest is proposed