Olfactory responses of Ips duplicatus from inner Mongolia, China to nonhost leaf and bark volatiles.

Leaf and bark volatiles from nonhost angiosperm trees were tested on Ips duplicatus by gas chromatographic-electroantennographic detection (GC-EAD) and by pheromone-baited traps in Sweden and Inner Mongolia, China, respectively. GC-EAD analysis of the headspace volatiles from fresh bark chips of Betula pubescens revealed trans-conophthorin, two green leaf volatiles (GLVs): 1-hexanol and (Z)-3-hexen-1-ol, and two C8 alcohols: 3-octanol and 1-octen-3-ol, that consistently elicited antennal responses by I. duplicatus. The identification of these EAD-active compounds was confirmed in further GC-EAD recordings with synthetic mixtures. Antennal responses were also found to synthetic (E)-2-hexen-1-ol and linalool, which have been identified from the leaves of nonhost birch and aspen species. No antennal responses of I. duplicatus were found to hexanal, (E)-2-hexenal, and (Z)-3-hexyl acetates. In field trapping experiments, blends of EAD-active green leaf alcohols or C8 alcohols, or transconophthorin alone resulted in significant reductions (27-60%) in the number of I. duplicatus captured compared with pheromone-baited traps. The unsuitable host compound, verbenone (Vn), also significantly reduced trap catches by up to 60% in both experiments. The strongest disruptive effect resulted from the addition of the combination of green leaf alcohols, C8 alcohols, and verbenone to the pheromone trap, which caused an 84% reduction in trap catch. The blend of two green leaf aldehydes plus the acetate increased the trap catches in 1998 and had no negative or positive effects in 1999. Our results suggest that these nonhost volatiles (NHVs) are important olfactory signals used by I. duplicatus in host selection. They may have great significance in developing semiochemical-based management programs for I. duplicatus by reducing or stopping attacks on suitable hosts.

Pheromonal secretions from glands on the 5th abdominal sternite of hydropsychid and rhyacophilid caddisflies (Trichoptera).

Extracts of different body parts of adult Trichoptera were tested for electrophysiological activity. Extracts of the IVth and Vth abdominal sternites of femaleHydropsyche angustipennis, Rhyacophila nubila, andR. fasciata, containing a paired exocrine gland, elicited significant electroan-tennographic responses when tested on conspecific male antennae. The paired gland occurs also in males of all the species, and inH. angustipennis, extracts from males were more active than female extracts when tested on male antennae. Female and male extracts from all species were analyzed by gas chromatography with simultaneous flame ionization and electroantennographic detection (EAD). EAD-active peaks in female extracts, stimulating male antennae, were identified inH. angustipennis as nonan-2-one; and inR. nubila andR. fasciata as heptan-2-one, heptan-2-ol, nonan-2-one, and nonan-2-ol. EAD-active components from maleH. angustipennis stimulating male antennae were octan-2-one, nonan-2-one (major peak), (Z)-6-nonen-2-one, decan-2-one, and a methylbranched decan-2-one. Female extracts and synthetic mixtures of compounds identified from femaleH. angustipennis andR. fasciata were tested for attractivity in the field. High catches with control traps obscured the results, but a synthetic mixture of the four identified compounds was significantly attractive and not different from female extracts for attracting maleR. fasciata. InH. angustipennis, a synthetic six-component male blend, in which nonan-2-one was the major component, attracted significant numbers of male and femaleH. angustipennis. Extracts of maleR. nubila andR. fasciata contained acetophenone and hexanoic and octanoic acids but did not have any electrophysiological or behavioral activity on either male or female antennae of conspecifics. The occurrence of a female sex pheromone inRhyacophila and an aggregation pheromone inHydropsyche corresponds to earlier described differences in mating behaviors in the Rhyacophilidae and Hydropsychidae.