FEEDING ACTIVITIES OF CICADULINA-MBILA (HEMIPTERA, CICADELLIDAE) ON HOST-PLANTS

The probing activities of the most important leafhopper vector of maiz e streak virus, Cicadulina mbila (Naude) (Hemiptera: Cicadellidae) wer e studied on different host-plants. Host preference was determined by giving the insects a choice of six plants, Digitaria sanguinalis, Zen mays, Zea perennis, Paspalum conjugatum, Oryza sativa and Saccharum of ficinarum (all Gramineae). Cicadulina mbila showed a strong preference for D. sanguinalis. Histological examination of plant tissues for sal ivary sheaths was used to reveal the preferred tissue. Cicadulina mbil a tended to ingest from the phloem of its preferred hosts, and switch to mesophyll or xylem tissue on less preferred hosts. The suitability of each host was assessed by measuring the weight gain and amount of h oneydew produced on each host by newly emerged adult females. Both par ameters were greatest on the preferred host. Probing behaviour was als o monitored electronically by recording the different waveform pattern s produced when insects were probing, ingesting or not probing on the selected hosts. Cicadulina mbila probed less frequently, ingested long er and spent less time in non-probing activities on its preferred host , D. sanguinalis, although these responses were similar on maize and s ugarcane. Rice induced poor probing responses and altered behaviour. T his interpretation of the waveforms was supported by histological exam ination. As maize streak virus (MSV) is not found in phloem sieve elem ents, prolonged ingestion from sieve cells would not account for effic ient acquisition from maize, which would require ingestion from other types of cells. D. sanguinalis was the host in which most ingestion fr om the phloem occurred, but it is the poorest source of MSV.