Identification of an aggregation pheromone for Pityogenes hopkinsi (Coleoptera : Scolytidae)

The aggregation pheromone of Pityogenes hopkinsi Swaine was identified; it is a three-component mixture, comprising chalcogran, cis-verbenol, and ethy l dodecanoate. Ethyl dodecanoate is new as a bark beetle pheromone componen t. Chemical analyses (GC-MS) were made on hindgut extracts from unmated and mated males and mated females collected in the field during colonization o f Pinus strobus L. (Pinaceae). Aerations from the naturally colonized logs were also analyzed to quantify the released amounts of the pheromone compon ents, a necessary preliminary step to making up biologically relevant doses for field bioassay. Beetles reared from infested host material in the labo ratory were introduced into logs of P. strobus, and the production and rele ase of pheromone components in relation to attack phase and "mating status" were described. In general, unmated males increased their production of ch alcogran and ethyl dodecanoate until females were admitted, after which pro duction ceased. A field subtractive bioassay showed that chalcogran was the key pheromone component, synergized by different compounds for the two sex es. Females exhibited their strongest response to a mixture of chalcogran a nd ethyl dodecanoate, whereas cis-verbenol was the synergist for male respo nse. Male-produced 1-hexanol had an inhibitory effect on male attraction to the aggregation-pheromone blend.