Herbivore-Induced Pine Cones And Host-Selection Of Dioryctria Pryeri Ragonot (Lepidoptera: Pyralidae)

Pine coneworm, Dioryctria pryeri Ragonot (Lepidoptera: Pyalidae), is an important insect pest of coniferous cones and shoots in China. In Chinese pine orchard of North China, the coneworm,accompanying with Gravitarmata margarotana (Heinemann), seriously damages cones of Chinese pine, Pinus tabulaeformis Carr., and causes more than 60% of the seed loss. Based on relationship of foodnet and chemical information net among Chinese pine—2 kinds of cone pests—parasitic wasps, the dissertation examined in detail effect of the infested cone by G. margarotana larvae on host selection of the coneworm larvae and adult moths, and examined the mechanism of herbivore-induced host susceptibility by means of chemical analysis and bioassay. The results as follow:(1)Feeding selection of the coneworm overwinter larvae and terpene compounds of conifer cones: The results of selection and preference of the larvae showed that the larvae of D. pryeri obviously trend and select P. tabulaeformis cone to P. armandi cone, and in selection experiments of uninfested and infested cones, and their extract with CH2Cl2 of P. tabulaeformis, the larvae obviously trend and select G. maigarotana-infested cone and its extract. The results of CH2Cl2-extracts and GC-MS analysis showed that specific monoterpene and sesquiterpene compounds areα-pinene,β-phellandrene,β-myrcene, D-limonene, T-mentha-1,4(8)-diene, geraniol ester acetic acid, germacrene D and caryophyllene, while specific diterpenes are thunbergol, retinol, 4,14-retro-retinol, pimaric acid,β-pimaric acid, 13-isopropylidene-podocarp-8(14) -en-15-oic acid, 4-flurobenzoic acid 1-adamantylethyl ester and (E)-labda-8(20),12,14-trien-19-oic acid, methyl ester etc. Terpenes of P. armandi cone are significantly different to Chinese pine cone, and diterpene content of P. armandi cone is obviously higher than Chinese pine cone.(2)Respone of Chinese pine cones to induction of exogenous methyl jasmonate and G. margarotana larvae: During the transferring-damaging period of the overwinter larvae of D. pryeri, the results of the cone-shoot headspace absorption, GC-MS analysis and enzyme active assay showed that methyl jasmonate (MeJA) treatment and G. margarotana larvae both induced conelets and cones of Chinese pine emitting specific volatiles—α-pinene,β-myrcene and D-limonene, and emitting amounts of infested cone volatiles was significantly more than conelets or MeJA treatment. Daytime emission of specific volatiles may be very important to host selection of parasite wasps. Meanwhile their polyphenol oxidase (PPO) andα-Chymotrypsin inhibitor (ChymPI) activity increased systemically after the conelet and cone was treated by exogenous MeJA and damaged by G.. maigarotana larvae, and the respone of the conelet to MeJA treatment and insect-damage was more sensitive than 2 years old cone. The free amino acid content and water content decreased, the crude fat content (resin) increased after the cone was damaged. These...