Leafhopper interactions with host plants – a role for volatile cues?

Abstract: Due to the sap-feeding nature of leafhoppers (Hemiptera: Cicadellidae), manytransmit disease-causing pathogens to economically important plants. When infected withplant pathogens, plant hosts may produce volatile profiles different to those of uninfectedplants, attracting insect vectors to infected plants and potentially increasing diseasetransmission. Although few studies have investigated the use of olfactory cues in host plantselection by leafhopper species, a push-pull strategy using semiochemicals to repel insectsfrom important crop plants toward a trap or trap crop is a promising alternative to chemicalcontrol. In a previous study, the leafhopper Mgenia fuscovaria (Stål), a vector of aster yellowsphytoplasma (AY) (‘Candidatus Phytoplasma asteris’) in grapevine Vitis vinifera L. in SouthAfrica, was found to be preferentially attracted to AY-infected grapevine branches. The modeof attraction, either visual or olfactory, was not determined. Analyses of the volatile organiccompounds produced by AY-infected and uninfected grapevine branches revealedquantitative and, in most cases, qualitative differences between infected and uninfectedbranches. However, behavioural bioassays with the leafhopper vector, as well as a literaturereview of other leafhopper species, suggest that olfactory cues, although important, arelargely supplementary to other stimuli, such as visual cues, for many leafhopper species.