Chemical cues used in host location by Phymastichus coffea, a parasitoid of coffee berry borer adults, Hypothenemus hampei

The wasp Phymastichus coffea LaSalle is a primary parasitoid that attacks adults of the coffee berry borer, Hypothenemus hampei Ferrari, the most serious pest of coffee in the world. We carried out a series of experiments in the laboratory to elucidate the role of chemical cues used by P. coffea during host location. In Y-tube olfactometer bioassays, P. coffea females were attracted to mechanically damaged and infested coffee berries, but not to uninfested ones. Immature stages and adults of H. hampei isolated from infested berries were not attractive to parasitoids, whereas the mixture of dust and frass collected from the infested berries was highly attractive. A dose-response experiment indicated a clear positive relationship between wasp response and the amount of dust/frass present. Females were significantly attracted to dust/frass originating from arabica (Coffea arabica L.) and robusta coffee (Coffea canephora Pierre ex Fröhner), but not to dust/frass originating from an artificial diet used for rearing H. hampei, or to dust/frass from a non-target host, Hypothenemus crudiae (Panzer). The results are discussed in relation to the natural history of P. coffea.