Mating disrupton by vibrational signals: theory and possible applications to Hemipteran pests

Planthoppers, leafhoppers, psyllids and white flies commonly damage important crops and are controlled by large amounts of chemical insecticides. In these taxa intraspecific communication is usually mediated via substrate-borne vibrational signals (VS) travelling along the plant tissues. In recent years, a number of studies have focused on the ability of leafhoppers and planthoppers to emit VS characterized by highly stereotyped and species-specific temporal and spectral parameters. VS are crucial to the mating success since they carry the information about species identity and enable location of a female. VS emitted by males trigger female reply. In this way, a male can track the VS from the substrate back to the source (the female) by using her VS as a directional cue. Since a vibrational male-female duet is the key factor in the mating behaviour, the interference or masking of the VS can be effective in the interruption of the whole mating communication. As a model for such approach we used the grapevine leafhopper Scaphoideus titanus Ball, however, the principles presented here can be extended to other species that use vibrational communication. In S. titanus it has been shown that in the laboratory conditions male rivalry noise (MRN, specific VS emitted by males aimed at interrupting an existing duet between another male and a female) played back into plant tissue effectively interrupted the mating duet. Similar trials were conducted also in a field-tunnel (length 10m, width 4m, median height 2.5m) on pairs of S. titanus placed on grapevine potted plants. Each plant was inserted in a cage. Four plants were positioned in a row and connected to each other by a tense iron wire. At the wire mid-length an electromagnetic shaker was set and programmed to continuously emit MRN sequences for 20 hrs. In total 50 pairs were subjected to the MRN treatment: 25 at distance 1m and 25 at distance 2m from the shaker. As a control, 25 pairs were put on caged plants without any vibrational treatment. Afterwards the females were collected and dissected after a period of 10 days to check the egg development, in order to determine whether they copulated. The MRN treatment proved to be highly effective in reducing the mating events: only 4% of the treated females were found fertilized, against 68% of the control. In conclusion, our preliminary results show a new possible approach for the control of pest insects that communicates by VS. The full potential of the method has still to be developed for S. titanus and applications also for other insects/plants models are conceivable.