The attraction of the red turpentine beetle,Dendroctonus valens, to the resin volatiles of its host,Pinus ponderosa, is elicited by three chiral monoterpenes. In field assays response was greatest to (S)-(-)-β-pinene; 92% (S)-(-)-α-pinene found inP ponderosa resin was not attractive. However, 75% (R)-(+)-α-pinene, which occurs inPinus lambertiana, a sympatric host ofD. valens, was attractive. (S)-(-)-α-Pinene interrupted response to (R)-(+)-α-pinene. (S)-(+)-3-Carene from both hosts was attractive at the (R)-(+)-α-pinene level. Three sympatric coniferous nonhosts each have the same attractive monoterpenes but produce less resin. These studies demonstrate the importance of chirality of host compounds in the host finding behavior of this bark beetle.
It was found that the turpentine of Pinus nelsonii contained 49.60% l‐α‐pinene, 41.50% l‐β‐pinene, 1.02 dipentene, 0.24% camphene, and 0.01% n‐heptane. The remainder contained 3.74% of oxygenated substances derived mainly from terpenes (including probably some oxygenated sesquiterpenes); about 0.02% of unidentified, low‐boiling materials, pot residue, and losses. The possible occurrence in P. nelsonii turpentine of the oxygenated materials should be rechecked, using freshly collected material. The identification of camphene and n‐heptane must be considered as tentative, only. The turpentine of Pinus occidentalis contained 63.8% d‐, dl‐α‐pinene, 22.2% l‐β‐pinene, 7.7% d‐Δ3‐carene, 1.8% methyl chavicol, 1.1% dipentene, 0.5% d‐longifolene, 0.3% linalool, 0.2% camphene, and 0.1% n‐heptane, with the remaining 2.3% accounted for by unidentified terpenes, pot residue, and losses. The identification of the last four constituents must be considered only tentative.
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