In 1984 a new research working party on mechanismsofwoody plant resistance against insects and pathogens(lUFROS2. 05-06) was formed in the International Union ofForestryResearchOrganizations. Thepurposeofthisworkingparty istostimulate and facilitate research progress in this areathroughenhancedcommunication among themany researchscientistsscatteredamongthevariouscountriesoftheworld. This volume istheresultofthe first internationalsymposiumofthisworkingparty which took place in Orleans. France on August 26-29 1986. Thanks are due to Institute Nationalde laRechercheAgronomique StationdeZoologie Forestiere fortheir in- strumental part in organizingthis symposium and to the University and the Cityof Orleansforgenerousfinancial support. The intentofthis proceedings is to (a) bring together adiverse array ofresearch resultsonthemechanismsofwoodyplantresistanceagainstdifferentkindsofinsects. and(b) to search for threadsofcommonality among these different plant/insect as- sociationstofurtherourfundamental understandingofhowplantsdefendthemselves againstphytophagousorganisms. Theresearchpapersareorganizedintothreemaingroups. Thefirstgroupexamines plant defenses from various basic physiological and ecological considerations. The remaining papers which are mainly case studiesofplant resistance against insects. arecategorizedon the basisofinsect intimacy with host tissues: (a) highly mobile. free feeders suchas moth larvae andsawflies and (b)poorlymobile attached or imbeddedfeederssuchasaphids scales miners andbarkbeetles. Eachofthesesections isfurtherorganizedonthebasisofkindoftissueattackedbytheinsects eitherleaves orstern/shootcortexand vasculartissues. Contents Preface v Contributors IX I. Basic Physiological and Ecological Considerations I. DefensiveStrategiesofWoody PlantsAgainst Different Insect-Feeding Guilds in Relation to Plant Ecological Strategiesand IntimacyofAssociation with Insects W. J. Mattson. R. K. Lawrence R. A. Haack D. A. Herms and p. J. Charles 3 2. Towards a UnifiedTheoryofPlant Defense A. A. Berryman. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3lJ 3. DefensiveResponsesofTrees inRelationtoTheirCarbon/NutrientBalance J. Tuomi P. Niemela F. S. Chapin 1II J. P. Bryant andS. Siren 57 4. GrowthandDifferentiation-BalanceRelationshipsinPinesAffectTheirRe- sistance to Bark Beetles(Coleoptera: Scolytidae) P. L. Lorio Jr. 73 5. SeasonalVariations inEnergySourcesandBiosynthesisofTerpenes in Maritime Pine C. Bernard-Dagan 93 6. Terpene Biosynthesis Under PathologicalConditions C. Cheniclet C. Bernard-Dagan andG.