Research: Ants eat more coffee borers on shade farms

Testing ant predation on the coffee berry borer in shaded and sun coffee plantations in Colombia. I. Armbrecht and M. C. Gallego. Entomologia Experimentalis et Applicata 124:261-267.

The study took place in Apia, Colombia (Risaralda dept., red on map). Prior to the 1990s, this was primarily a shade coffee region, but outside owners came converted farms to sun coffee. Annually about 5% of the crop is lost to the coffee borer or broca, Hypothenemus hampei, an African pest which arrived in Colombia in 1988.

Three shaded and three sun coffee plantations were examined. Canopy cover averaged 79% with 302 shade trees per hectare in shade farms, and 29% and 33 trees per ha in sun farms. A previous study in the same farms found a higher leaf litter ant diversity in shaded farms than sun farms (32.3 species per square meter versus 24.3). Although most of the life of the broca is spent inside the coffee cherry, fallen infected cherries are an important source of infestation, so studying the impact of ground ants is relevant. Previous studies in Colombia have also found that ants feed on broca at all their life stages.

More ant species (16) were attracted to broca in shade farms than sun farms (12). More broca adults were removed from traps by ants in shade farms (30.5%) than in sun farms (15.5%).  This provides strong evidence that native ground-dwelling ants are attracted to and feed on broca adults, and that shade management has a positive effect on this biocontrol. The introduction of the broca in Colombia has led to a dramatic increase in pesticide use, which may also be negatively impacting ant biodiversity.

The two shade plantations that had greater than 10 species of shade trees and used no pesticides in this study are la Playita and la Esperanza (not to be confused with the better-known Esperanza estate from Huila, Colombia, H on map). I did not find any sources of coffee from these specific farms, so they may only be contributing to a cooperative.