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Analyses of pentane extracts of frass, whole beetles, and volatiles trapped on Porapak-Q from Pityophthorus Eichhoff spp. fed on Pinus radiata D. Don demonstrated that (E)-pityol [2-(1-hydroxy-1-methylethyl)-5-methyltetrahydrofuran] was produced by male Pityophthorus carmeli Swaine, female Pityophthorus nitidulus (Mannerheim), and female Pityophthorus setosus Blackman. (E)-(−)-Conophthorin) [(5S,7S)-(−)-7-methyl-1,6-dioxaspiro[4.5]decane] was produced by male P. carmeli and male P. nitidulus. Only the (2R,5S)-(+) stereoisomer of (E)-pityol was produced by male P. carmeli and female P. setosus. In field bioassays in central coastal California, P. setosus was attracted to (E)-(+)-pityol, whereas P. carmeli responded only to a combination of (E)-(−)-conophthorin and (E)-(+)-pityol. Male P. setosus and female P. carmeli responded to these treatments with larger numbers than opposite-sex conspecifics. (E)-(−)-Conophthorin alone did not attract species of Pityophthorus but significantly reduced catches of P. setosus to (E)-(+)-pityol. Lasconotus pertenuis Casey (Coleoptera: Colydiidae) and Ips mexicanus (Hopkins) (Coleoptera: Scolytidae) were attracted to a combination of (E)-(−)-conophthorin and (E)-(+)-pityol, and showed a trend for attraction to all (E)-(−)-conophthorin-containing treatments. (E)-(−)-Pityol was neither attractive nor interruptive for any taxon. (E)-(+)-Pityol is shown to be an aggregation pheromone component for P. carmeli and P. setosus. (E)-(−)-Conophthorin functions as a pheromone component for P. carmeli and may also function as a synomone that decreases competition of P. carmeli and P. nitidulus with P. setosus and as a kairomone for L. pertenuis. These semiochemicals have been useful in studying relationships among twig insects and the pathogen Fusarium circinatum (Nirenberg and O’Donnell), causal agent of pitch canker disease in P. radiata.

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The walnut twig beetle (WTB),Pityophthorus juglandisBlackman (Coleoptera: Curculionidae), vectors a fungus,Geosmithia morbidaKolařík, Freeland, Utley, and Tisserat (Ascomycota: Hypocreales), which colonises and kills the phloem of walnut and butternut trees,JuglansLinnaeus (Juglandaceae). Over the past two decades, this condition, known as thousand cankers disease (TCD), has led to the widespread mortality ofJuglansspecies in the United States of America. Recently the beetle and pathogen were discovered on severalJuglansspecies in northern Italy. Little is known about the extra-generic extent of host acceptability and suitability for the WTB. We report the occurrence of both the WTB andG. morbidain three species of wingnut,Pterocarya fraxinifoliaSpach,Pterocarya rhoifoliaSiebold and Zuccarini, andPterocarya stenopterade Candolle (Juglandaceae) growing in the United States Department of Agriculture-Agricultural Research Service, National Clonal Germplasm Repository collection in northern California (NCGR) and in the Los Angeles County Arboretum and Botanic Garden in southern California, United States of America. In two instances (once inP. stenopteraand once inP. fraxinifolia) teneral (i.e., brood) adult WTB emerged and were collected more than four months after infested branch sections had been collected in the field. Koch’s postulates were satisfied with an isolate ofG. morbidafromP. stenoptera, confirming this fungus as the causal agent of TCD in this host. A survey of the 37PterocaryaKunth accessions at the NCGR revealed that 46% of the trees had WTB attacks and/or symptoms ofG. morbidainfection. The occurrence of other subcortical Coleoptera associated withPterocaryaand the first occurrence of the polyphagous shot hole borer, a species nearEuwallacea fornicatusEichhoff (Coleoptera: Curculionidae), inJuglansare also documented.

The polyphagous shot hole borer (PSHB), Euwallacea sp., was first detected in 2003 in Los Angeles County, California, USA. Recently, this invasive species has become a major pest of many hardwood trees in urban and wildland forests throughout southern California. PSHB is nearly identical in morphology and life history to the tea shot hole borer (TSHB), Euwallacea fornicatus, an invasive pest of hardwoods in Florida, USA and many other parts of the world. However, molecular studies have suggested that the taxa are different species. We conducted morphometric and chemical analyses of the phenotypes of Euwallacea sp. collected in southern California (Los Angeles County) and E. fornicatus collected in Florida (Miami-Dade County). Our analyses indicated that PSHB has 3 larval instars. The third larval instar was separated from the first 2 instars by head capsule width with 0 probability of misclassification. The body length, head width, and pronotal width of PSHB adult males were significantly less than those of females. Head width and pronotal width of female PSHB were significantly less than those of female TSHB. In contrast, body length, and ratio of body length to pronotal width of female PSHB were significantly greater than those of female TSHB. However, females of these 2 species could not be separated completely by these 4 measurements because of the overlapping ranges. Cuticular hydrocarbons detected in both species were exclusively alkanes (i.e., n-alkanes, monomethylalkanes, dimethylalkanes, and trimethylalkanes). Cuticular hydrocarbon profiles of PSHB males and females were similar, but they both differed from that of TSHB females. Cuticular hydrocarbons of PSHB were predominantly internally branched dimethylalkanes with backbones of 31 and 33 carbons, whereas cuticular hydrocarbons of TSHB females were dominated by internally branched monomethylalkanes and dimethylalkanes with backbones of 28 and 29 carbons. Multiple compounds within these classes appear to be diagnostic for PSHB and TSHB, respectively.