THE IMPORTANCE OF MONOTERPENES IN THE AGG REGATION OF THE SPRUCE BARKBEETLE IPS-TYPOGRAPHUS (COLEOPTERA, SCOLYTIDAE, IPINAE)

Field bioassays show that the aggregation of the spruce bark beetle Ip s typographus (Linnaeus 1758) to pheromone baited traps is affected by monoterpenes. The mixture of (-)-alpha-pinene and (+)-limonene attrac ts the adults significantly (2 mi of each compound per dispenser) wher eas the individual components are ineffective. The application of (-)- beta-myrcene reduces the trap catch to 33%. (+)-alpha-pinene acts as a repellent; only 6% of the trap catch of the control can be observed. The last-mentioned compound inhibits the colonization of trap trees by I typographus. Trap trees felled in winter can be devided in two grou ps with regard to the colonization by I typographus: (1) Uninfested tr ees are found to have only small amounts of monoterpenes in the inner bark which decrease only little in the interval between the date of fe lling and the dispersal of the beetles. (2) Trees which are colonized have higher concentrations of terpenes in the bast which are diminishe d significantly until I typographus initiated the brood systems. But t he amounts of monoterpenes in the inner bark of colonized trap trees a re higher compared to those which remain uninfested. I typographus is found to colonize parts of the stem which are characterized by an opti mum concentration of the key monoterpene (-)-alpha-pinene ranging betw een 0.08 - 0.35 nmol/mg fresh matter. The density of brood systems cor relates with an index value which is calculated from the concentration s of (-) and (+)-alpha-pinene, (+)-limonene, and (-)-beta-myrcene.