Shade has antagonistic effects on coffee berry borer

This work was addressed to clarify shade effects on the coffee berry borer, Hypothenemus hampei (Coleoptera: Curculionidae). The research was carried out in 2010, in Turrialba, Costa Rica, at 600 m of elevation, in a trial established by CATIE where different shade trees and coffee managements are compared. We studied several combinations of three levels of exposure to light (full sun, medium shade of Erythrina poeppigiana, dense shade of E. poeppigiana and Chloroleucon eurycyclum) and three coffee managements (organic with applications of the entomopathogen fungus Beauveria bassiana, conventional with insecticide sprays, and conventional insecticide-free). The response variables were: (i) populations of H. hampei in green, ripe and dry berries, and (ii) number of bored berries. We also monitored the microclimate in full sun exposure and dense shade conditions. Shade tended to increase H. hampei populations into coffee berries. With the conventional management, with insecticide or with no pest control, the number of CBB females, into the ripe and dry berries from the branch, was 70 % higher on average under shade than at full sun exposure. When analyzing the percentage of bored berries, we observed almost the same trend. With the conventional management, with insecticide, shade significantly increased the proportion of berries bored by the insect: 6.4 % and 2.4 % of bored green and ripening berries at the beginning of the harvest under dense shade and at full sun exposure respectively. However, shade effect was reversed when B. bassiana was applied. The proportion of bored berries was significantly higher under the moderate shade (4.9 %) as compared with the dense shade (4.0 %). Shade has therefore antagonistic effects on H. hampei. In one side, shade increases CBB populations when no B. bassiana is applied, but in the other side, it decreases the number of bored berries when the entomopathogen fungus is sprayed. This can be explained by the microclimatic conditions which were more favorable to the insect and to the entomopathogen fungus under shade. Under dense shade, temperatures were buffered (particularly high temperatures) and relative humidity and plant organs wetness were higher as compared to full sun exposure. (Résumé d'auteur