Effect of lure age and blend on sex pheromone trap catches of the mirid Sahlbergella singularis on cacao in Ghana

Abstract

Mirids, Sahlbergella singularis and Distantiella theobroma (Heteroptera: Miridae), are the main cacao pests in West Africa. Females of both species produce sex pheromones composed of hexyl (R)-3-((E)-2-butenoyl)-butyrate and hexyl (R)-3hydroxybutyrate, the major and minor components, respectively. Lures composed of 1000:500 µg blends of the two components pre-aged for 2, 4, 8 and 12 weeks were compared with fresh lures in a field experiment in Ghana. Lures were replaced monthly. A total of 272 S. singularis, all male, was caught. Fresh lures and those preaged for 2 and 4 weeks caught similar numbers in a month while lures pre-aged for 8 and 12 weeks caught 34 % and 26 %, respectively, than fresh lures. The attractiveness of five different pheromone blends were compared in a 15-month field trapping experiment. A total of 701 S. singularis, all male, was caught. The highest numbers were caught in traps releasing both components with no significant difference among 1000:50, 1000:500 and1000:1000 µg blends. Traps releasing hexyl (R)-3-((E)-2butenoyl)-butyrate alone caught fewer individuals than two-component blends, and 2 those releasing hexyl (R)-3-hydroxybutyrate alone caught similarly low numbers to unbaited controls. We recommend that 2:1 blend lures, renewed at least bi-monthly are used for mass-trapping cacao mirids. The results are discussed in relation to previously published mirid pheromone blend optimisation and longevity studies.