Trials to assess the effectiveness of new synthetic pheromone mixtures for trapping Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) in maize stores

Male Prostephanus truncatus produce an aggregation pheromone known as "Trunc-call", the major component of which (T1: 1-methylethyl(E)-2-methyl-2-pentenoate) has been used for some years in lures in traps for monitoring beetle populations. A second component of the pheromone (T2: 1-methylethyl(E,E)-2,4-dimethyl-2,4-heptadienoate) has recently been identified. Experiments were carried out to compare mixtures of T1 and T2 with T1 alone and to determine the effective lives of the pheromone lures under local storage conditions. More beetles were caught in traps containing pheromone mixtures than those containing T1 alone although significant differences could not be shown between any of the mixtures tested. It was concluded that the current monitoring system could possibly be improved by using a mixture of T1 and T2 as the pheromone lure. T1 was released faster from the vials than T2, but at least 19% of each component remained after 2 weeks exposure. It is however recommended that lures are renewed every two weeks when used with the P. truncatus trap.