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: I-a, multiple-cell laceration; and I-c, continuous ingestion without stylet movement. Number of probes per insect did not differ significantly among water treatments. Mean number of waveform events per insect, I-c waveform events per insect, waveform events per probe, I-c waveform events per probe, and I-a waveform events per probe, occurred significantly more often on high and moderate water than on low water. Probing duration per insect, I-a waveform duration per insect, and I, waveform duration per event were not significantly different among water treatments. Duration of I-c waveforms per insect were significantly longer on low water than on high or moderate water, whereas duration of I-a tended to be longer on high and moderate water. Probing duration per probe was not significantly different among water treatments. Duration of I-a waveform per probe was significantly longer on high and moderate water than on low water, whereas duration of I-c was significantly longer on low water than on high and moderate. Probing duration per event and I-c 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 I-a to I-c waveforms, the latter being a behavior that is less injurious to the plant.