Effects of verbenone dose and enantiomer on the interruption of response of the red turpentine beetle, Dendroctonus valens LeConte (Coleoptera: Scolytidae), to its kariomones

The effects of different doses and enantiomers of verbenone on the interruption of response of red turpentine beetle, Dendroctonus valens LeConte (Coleoptera: Scolytidae), a very aggressive and destructive exotic pest, were conducted using electoantennogram (EAG) assays and behavioral tests in the laboratory and field, No significant differences were found between antennal responses of D. valens by sex, and only one significant difference occurred between their responses to equivalent doses of the (S)-(-) and (R)-(+) enantiomers. Antennal responses to increased doses of (S)-(-)-verbenone reached a plateau at 0.1 mu g, whereas the amplitude of response to increased dosages of (R) - (+) -verbenone continued to rise. In a laboratory bioassay, (S) - (-) -verbenone at a stimulus load of 0.1 mu g synergized D. valens response to a kairomone blend; but at higher stimulus loads (10 and 100 mu g), it functioned as a repellent. In field trials using funnel traps, both (S)-(-)- and (R)-(+)-verbenone bubblecaps inhibited the response of D. valens to the host kairomone blend. These results indicate that verbenone functions as a multipurpose pheromone for D. valens.