Probing Behavior of Potato Leafhopper (Homoptera: Cicadellidae) on Alfalfa Influenced by Plant Water Deficit

Probing behavior of adult potato leafhopper, Empoasca fabae (Harris), on alfalfa, Medicago sativa L., plants maintained at 3 water levels, was monitored using an AC electronic feeding monitor. Two waveform feeding types were predominant in occurrence and duration: Ia, multiple-cell laceration; and Ic, continuous ingestion without stylet movement. Number of probes per insect did not differ significantly among water treatments. Mean number of waveform events per insect, Ic waveform events per insect, waveform events per probe, Ia waveform events per probe, and Ic waveform events per probe, occurred significantly more often on high and moderate water than on low water. Probing duration per insect, Ia waveform duration per insect, and Ia waveform duration per event were not significantly different among water treatments. Duration of Ic waveforms per insect were significantly longer on low water than on high or moderate water, whereas duration of Ia tended to be longer on high and moderate water. Probing duration per probe was not significantly different among water treatments. Duration of Ia waveform per probe was significantly longer on high and moderate water than on low water, whereas duration of Ic was significantly longer on low water than on high and moderate. Probing duration per event and Ic waveform duration per event were significantly longer on low water than on high and moderate. Water deficit in alfalfa results in a shift of probing behavior in potato leafhopper from predominantly Ia to Ic waveforms, the latter being a behavior that is less injurious to the plant.