Seasonal Terpene Variation in Needles of Pinus radiata (Pinales: Pinaceae) Trees Attacked by Tomicus piniperda (Coleoptera: Scolytinae) and the Effect of Limonene on Beetle Aggregation.

Concentrations of four monoterpenes were determined in needles of Pinus radiata (D.Don) (Pinales: Pinaceae) trees that were attacked or nonattacked by Tomicus piniperda (L.) (Coleoptera: Scolytinae). Compounds were identified and quantified by gas chromatography-mass spectrometry. The mean ambient temperature was obtained using climate-recording data loggers. The effect of limonene on field aggregation was also evaluated at three limonene release rates using Lindgren attractant-baited traps and trap logs. Attacked trees produced less α-pinene in March, July, and November than nonattacked trees, less β-pinene in July and November, and less limonene from May to November. Limonene reduced the attraction of T. piniperda to attractant-baited traps and trap logs. Results were linked to better responses to high temperatures, with respect to terpene contents, by the nonattacked trees after the spring attack.