Effect of needle damage on the release rate of Masson pine (Pinus massoniana) volatiles

The effect of needle damage on the release rate of Masson pine (Pinus massoniana Lamb.) volatiles was examined. Needles were continuously damaged by mechanical damage (MDP) or by feeding of pine caterpillar (Dendrolimus punctatus) larvae (LFP); undamaged pine was used as a control (UDP). Volatiles were collected before damage, and at 16, 24, 40, 48, 64, 72, 88 and 96 h post-damage, and analyzed. The analyses revealed that 19 compounds identified as constitutive volatiles from UDP were terpenes and green leaf odors. The release rate of volatiles from MDP or LFP was higher than that from UDP. At 96 h post-damage, emission from MDP or LFP returned to the same level as that of UDP. Some volatiles, including sabinene, ocimene, limonene-1,2-epoxide, linalool, linalool acetate, germacrene D-4-ol, farnesol, and (E)-4,8-dimethyl-1,3,7-nonatriene were induced by mechanical damage and/or larval attack. Furthermore, the release rate of linalool acetate, farnesol, or (E)-4,8-dimethyl-1,3,7-nonatriene from LFP was higher than that from MDP. Based on an exact estimation of the proportion of damaged pine needles, a significant linear correlation between the release rate of total volatiles identified and the proportion of damaged needles was found in the case of LFP but not MDP.