The Ecology of a Natural Population of the Queensland Fruit Fly, Dacus Tryoni. Vi. Seasonal Changes in Fruit Fly Numbers in the Areas Surrounding the Orchard.

Abstract

Cuelure traps were set out over a wide area surrounding the Wilton orchard and checked regularly between February 1968 and January 1971. The trap catches indicated that fluctuations in fruit fly numbers in the different habitats followed similar trends from year to year with peaks in September, December and late February. Mark-recapture studies carried out in 1969 (a typical year) indicated that the density of mature adults in the dry sclerophyll bushland to the east of the orchard during the largest of these peaks in late February was around 6256 per km2 (16,000 per square mile). Estimates based on these data indicated that pairs of cuelure traps spaced 0.4 km (0.25 miles) apart along a trap line in sclerophyll bushland caught approximately 8 % of the males per week in the surrounding area of 0.16 kmz (0.0625 square miles). Other data indicated that in the spring of 1969 the weekly mortality rate of adults was around 0.194. It is suggested that the majority of D, tryoni which migrate into the orchard and the surrounding areas come from Wollongong and Sydney and that the presence of these two large urban areas has a marked effect on the abundance of D. tryoni in the general area.