Differential effects of ants as biological control of the coffee berry borer in Puerto Rico

Abstract

Conservation biological control consists of managing agroecosystem to maintain and enhance the action of natural enemies. Agroforestry systems such as shaded coffee system has been shown to maintain high diversity of organisms, including predators and parasitoids of insect pest. The coffee berry borer (CBB), Hypothenemus hampei, is one of the most widely distributed coffee pests frequently causing severe economic damage. Ants have been reported as natural enemies of the CBB, but different species of ants are known to have different and sometime contrasting effects against the CBB. In this study, we examine the damage and survival of CBB on coffee plants that are dominated by six different species of ants, Solenopsis invicta, Wasmannia auropunctata, Monomorium floricola, Paratrechina longicornis, Brachymyrmex heeri and Pheidole moerens, in Puerto Rico. This represents a novel community of natural enemies since four of the six species are non-native. We hypothesized that the large and dominant species, S. invicta, would reduce the damage of the CBB by preying on adult CBB outside the berries, while the smaller species, would reduce the survival of the CBB by preying on the reproducing adults inside the berries (and potentially also on the immature stages, although not quantified in this study). Results show that S. invicta was associated with significantly reduced CBB damage. The only species associated with reduced survival of CBB inside berries was W. auropunctata, whereas the others were not associated with any effect on survival. Surprisingly, P. moerens and P. longicornis had a significant positive effect on the damage of the CBB suggesting that these species could only forage on plants that did not harbor S. invicta or W. auropunctata, the two most aggressive ants both of which were associated negatively with the CBB. The study also suggests that the negative impact of S. invicta on W. auropunctata indirectly facilitates the CBB by protecting it from predation by W. auropunctata once the adult CBB gains entrance to the coffee berry.