Prediction of upsurges in populations of the insect vector (Trioza erytreae, Hemiptera: Triozidae) of citrus greening disease using low-cost trapping.
Populations of Trioza erytreae, a vector of the serious citrus greening (bacterial) disease, were monitored using fluorescent yellow sticky traps in 4 mature orange orchards in South Africa. The overall value for b in L.R. Taylor's power law was 1.54, indicating moderately clumped spatial distribution. A threshold of 2 or more adults per set of 3 traps on 2 consecutive weeks was the threshold leading to a population upsurge. At low altitudes (350 m), the population variability (anti-logarithm 3 × standard deviation of logarithmic raw data) was such that the maximum population level was 1.4 times that of the minimum. At higher altitudes (720 m), the maximum was 78 times the minimum. Both mean population levels (in logarithmic transform) and variability were positively correlated with altitude. Population upsurges were, therefore, most extreme at higher altitudes. T. erytreae was evenly spread across irrigated and non-irrigated citrus monoculture, and across natural bush vegetation. Proposals are made for improving management of T. erytreae and citrus greening by monitoring the population of the pest with this method of trapping.