Semiochemicals from three species of Pityophthorus (Coleoptera : Scolytidae): Identification and field response

Analyses of pentane extracts of frass, whole beetles, and volatiles trapped on Purapak-Q from Pityphthorus Eichhoff spp. fed on Pinus radiata D. Don d emonstrated that (E)-pityol [2-(1-hydroxy-1-methylethyl)-5-methyltetrahydro furan] was produced by male Pityophthorus carmeli Swaine, female Pityophtho rus nitidulus (Mannerheim), and female Pityophthorus setosus Blackman. (E)- (-)-Conophthorin [(5S,7S)-(-)-7-methyl-1,6-dioxaspiro[4.5]decane] was produ ced by male P. carmeli and male P. nitidulus. Only the (2R,5S)-(+) stereois omer of (E)-pityol was produced by male P. carmeli and female P. setosus. I n field bioassays in central coastal California, P. setosus was attracted t o (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 conspe cifics. (E)-(-)-Conophthorin alone did not attract species of Pityophthorus but significantly reduced catches of P. setosus to (E)-(+)-pityol. Lascono tus pertenuis Casey (Coleoptera: Colydiidae) and Ips mexicanus (Hopkins) (C oleoptera: Scolytidae) were attracted to a combination of (E)-(-)-conophtho rin and (E)-(+)-pityol, and showed a trend for attraction to all (E)-(-)-co nophthorin-containing treatments. (E)-(-)-Pityol was neither attractive nor interruptive for any taxon. (E)-(+)-Pityol is shown to be an aggregation p heromone component for P. carmeli and P. setosus. (E)-(-)-Conophthorin func tions as a pheromone component for P. carmeli and may also function as a sy nomone that decreases competition of P. carmeli and P. nitidulus with P. se tosus and as a kairomone for L. pertenuis. These semiochemicals have been u seful in studying relationships among twig insects and the pathogen Fusariu m circinatum (Nirenberg and O'Donnell), causal agent of Ditch canker diseas e in P. radiata.