Mode of Expression of Host Preference by Circulifer tenellus, the Vector of Curly Top Virus123

Abstract

Beet leafhoppers were presented with a choice between a preferred host, sugarbeet, and a nonpreferred host, tomato, by 3 different methods, involving both seedling and young growing plants. Leafhoppers moved to preferred and nonpreferred hosts without distinction provided foliar surface areas of the 2 species were similar in size. Within seconds after alighting upon either species, leafhoppers routinely chose a spot where they remained very still as though feeding. This still period of apparent feeding lasted an average of 24 minutes on tomato and 36 minutes on sugarbeet under natural conditions. It lasted twice as long when leafhoppers were captured, caged, and starved for 2 hours immediately before testing. At the end of the still period, leafhoppers promptly flew away from tomato plants, but on sugarbeets they usually moved about for a time and then settled down to an extended period of stillness. Both preferred and non preferred hosts were infected during the initial still period in tests with viruliferous leafhoppers. Apparently the leafhopper: (1) finds preferred hosts by random movement from plant to plant; (2) does not discriminate until after spending 25 to 50 min on a plant; (3) feeds on both preferred and non preferred hosts before discriminating; and (4) expresses preference by departing from non preferred and remaining on preferred hosts.