Initiation of stylet penetration by aphids depends on the sensory assessment of a number of plant surface features including colour, texture and phytochemicals (volatile and non-volatile). Video recording behaviour of the black bean aphid, Aphis fabae, showed that these insects rapidly inserted their stylets following contact with host plants (beans), but were reluctant to penetrate non-hosts (oats). However, when epicuticular waxes were stripped from oats, using cellulose acetate, aphids penetrated the plant surface significantly earlier than on oats with the wax layer intact. Chloroform extraction of epicuticular lipids, followed by coupled gas chromatography-mass spectrometry, revealed a complex blend of wax components on beans, whereas one compound (1-hexacosanol) predominated on oats. Epicuticular lipids were applied to artificial (glass) substrates in order to investigate their behavioural activity. Initiation of a stylet penetration attempt by A. fabae was delayed when the oat extract or pure 1-hexacosanol were applied, but the bean extract had no behavioural effect. The results suggest that epicuticular lipids play an important role in the early stages of host-plant selection by A. fabae.

Initiation of stylet penetration by aphids depends on the sensory assessment of a number of plant surface features including colour, texture and phytochemicals (volatile and non-volatile). Video recording behaviour of the black bean aphid, Aphis fabae, showed that these insects rapidly inserted their stylets following contact with host plants (beans), but were reluctant to penetrate non-hosts (oats). However, when epicuticular waxes were stripped from oats, using cellulose acetate, aphids penetrated the plant surface significantly earlier than on oats with the wax layer intact. Chloroform extraction of epicuticular lipids, followed by coupled gas chromatography-mass spectrometry, revealed a complex blend of wax components on beans, whereas one compound (1-hexacosanol) predominated on oats. Epicuticular lipids were applied to artificial (glass) substrates in order to investigate their behavioural activity. Initiation of a stylet penetration attempt by A. fabae was delayed when the oat extract or pure 1-hexacosanol were applied, but the bean extract had no behavioural effect. The results suggest that epicuticular lipids play an important role in the early stages of host-plant selection by A. fabae.

Colupulone, the main component of the beta-acid fraction of hop extracts, was shown to repel the two-spotted spider mite Tetranychus urticae Koch from the surface of plant leaves. The total beta-acid fraction was found more effective in repelling the mites and reducing the number of eggs laid than colupulone at equivalent concentrations, suggesting that other components of the extract have repellent and oviposition-deterring effects.

The behavioural responses of adult female western flower thrips, Frankliniella occidentalis (Pergande) to volatiles from meadow-sweet (Filipendula ulmaria), bay laurel (Laurus nobilis) and sage (Salvia officinalis) were investigated in laboratory bioassays. Volatiles collected by entrainment of a solvent extract of F. ulmaria were more attractive than was the original extract. Frankliniella occidentalis was also significantly attracted to volatiles from L. nobilis and S. officinalis. Analysis by gas chromatography and mass spectrometry identified 1,8-cineole (eucalyptol) as one of the main volatile components of all three plant species. In coupled gas chromatography-electroantennography studies with F. ulmaria, both 1,8-cineole and methyl salicylate elicited responses from F. occidentalis. Eucarvone was identified as the major component of F. ulmaria volatiles, but showed no electrophysiological activity. Behavioural responses of thrips to a range of concentrations of 1,8-cineole and methyl salicylate were tested using a modified Pettersson 'star' olfactometer. 1,8-Cineole showed some attractant activity for the thrips at 0.01 mg, but methyl salicylate was repellent at all the concentrations tested.Resume-La reponse comportementale de femelles adultes de thrips (Frankliniella occidentalis) aux emissions volatiles de trois plantes aromatiques, la filipendule (Filipendula ulmaria), le laurier-sauce (Laurus nobilis) et la sauge (Salvia officinalis), a ete etudiee dans des essais au laboratoire. Les produits volatils obtenus par collecte d'effluves d'un extrait par solvant de F. ulmaria se sont montres plus attractifs que l'extrait original. Frankliniella occidentalis a aussi ete attire significativement par les emissions volatiles de L. nobilis et S. officinalis. Des analyses par chromatographie en phase gazeuse et spectrometrie de masse ont permis d'identifier le 1,8-cineole (eucalyptol) comme l'un des composes volatils majeurs des trois especes vegetales. Dans des etudes par couplage chromatographie en phase gazeuse-electroantennographie, avec un extrait de F. ulmaria, le 1,8-cineole et le methyl salicylate ont tous deux induit des reponses chez F. occidentalis. L'eucarvone a ete identifie comme le compose majoritaire des emissions volatiles de F. ulmaria, mais n'a induit aucune activite electrophysiologique. Les reponses comportementales des thrips a une gamme de concentrations de 1,8-cineole et de methyl salicylate ont ete evaluees dans im olfactometre de Pettersson modife. Le 1,8-cineole a induit une certaine attraction chez les thrips a la concentration de 0,01 mg, mais le methyl salicylate a ete repulsif a toutes les concentrations testees.

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