Interruption of aggregation pheromone in Ips typographus (L.) (Col. Scolytidae) by non-host bark volatiles

1 The antennally active nonhost bark volatiles (NHVs): trans-conophthorin (tC), C-6-alcohols (green leaf volatiles; GLVs) and C-8-alcohols, were tested for their ability to reduce attraction of the spruce bark beetle Ips typographus (L) (Col. Scolytidae) to its pheromone sources in both laboratory walking bioassy and field trapping experiments. 2 In the walking bioassay with I. typographus females, individual NHVs such as tC, 3-octanol and 1-octen-3-ol, and the unsuitable host signal, verbenone (Vn), were inactive at the doses tested. However, the blend of C-6-alcohols (3GLVs) and all the binary, ternary, or quarternary blends significantly reduced the female attraction to the pheromone sources. 3 In the field trapping experiments, individual NHV signals (tC, C-6-alcohols and C-8-alcohols) all reduced catch of I. typographus in pheromone-baited traps, with their inhibitory effects similar to that of the known inhibitor, Vn. The binary, ternary or quarternary combinations of these NHV signals or Vn, all caused significantly stronger reductions in trap catches than the individual signals. The blends showed similar levels of interruption, except the binary blend of C-8-alcohols (2C8OH) and Vn. 4 Difference in trapping mechanism between pipe traps (attraction and landing) and Lindgren funnel traps (attraction) did not affect the pattern of inhibition of these active NHV signals and Vn. 5 These behaviourally active nonhost volatiles and Vn might be used effectively to protect spruce trees or stands against attacks by I. typographus.