Host-derived volatiles as attractants and pheromone synergists for driedfruit beetleCarpophilus hemipterus

The attractiveness of representative host materials, host extracts, and individual host volatiles (primarily carboxylic acids, alcohols, and esters) toCarpophilus hemipterus (L.) (Coleoptera: Nitidulidae) adults in wind-tunnel bioassays was examined. Attractiveness of the materials was examined alone and in combination with the aggregation pheromone. Host materials and extracts were often attractive on their own, and the attractancy was synergized when they were combined with the pheromone. Propanoic and butanoic acids, methanol, 2-propanol, 1-heptanol, methyl butanoate, and propanal were among the most effective attractants relative to the pheromone, but many other compounds significantly synergized the pheromone (typically three- to four fold). Attractiveness and synergism were influenced by the carbon chain length and branching of the substitutents. Straight-chain compounds that had at least three carbon atoms were generally effective as synergists. Many branched-chain compounds were also effective synergists. In general, the degree of attractiveness and synergism could be predicted fairly well with the physicochemical steric (Es) parameter, although the lipophilicity (Pi) parameter also appeared to be useful in explaining the lower activity of short-chain substituents. Thus, many compounds that had only limited attractiveness on their own may nevertheless play and important role in synergizing the pheromone. Structure-activity studies appear to be appropriate not only for determining optimal attractants for these insects, but also for determining effective synergists for the pheromone.