ABC News reported on February 3 that
“A 15-kilometre suspension zone now extends on both sides of the Murray River around the sites and fruit from inside the zone will not be allowed into some markets and will need to be cold-treated for others.
“Agriculture Minister Peter Walsh says it is likely the pests were introduced in fruit from other areas and ideal weather allowed them to survive.”
I doubt that such quarantine barriers to this tiny flying insect make any difference, however. I lived as a child on a small fruit farm in the ranges behind Brisbane, and my father researched the fruit fly pestilence at great length, finally publishing his history of the pest as Of Peaches and Maggots – The Story of Queensland Fruit Fly (A.C. Courtice, Hillside Books 2006).
For a long time, it was thought that the adult fruit fly lived a brief life after hatching from pupation, and travelled only a short distance from where it pupated. However, there is enough evidence to abandon this idea, especially when you consider there may be several generations in one season.
The conclusion of my father is that fruit flies
"travelled inland in September and continued southwest into summer (as far as Adelaide in a wet year) before a last generation returns east in autumn, rather like the Pelicans that return from Lake Eyre when the riverland becomes dry; when temperatures fall and the southeast trade winds are beginning to blow. Marked flies released at Wangaratta in autumn moved northeast toward the coast, confirming that the ultimate progeny of migrants from central Queensland come to East Gippsland."
Speaking of the closely related (and more easily caught) Wild Tobacco fruit fly, Dacus cacuminatus, my father relates that
"The men went further west and caught more at Percy Walker’s place at Glen Lyon, 50 miles beyond the last tobacco berry. Years later I caught them at 150 miles at Goondiwindi, and Dr May saw them moving through St George, 240 miles out."
In the wet, humid weather we have had this year it would be ideal conditions for the flies to migrate. The wet encourages their breeding cycle, and provides much greater supplies of the leaf-surface bacteria that the adult fly lives off. Climate change may not bring wet weather every year but as climatic zones move away from the equator the range of the fly is sure to extend more often.
Searching for scapegoats and erecting strict quarantines is likely to be a waste of time. A better understanding of the fly and its life cycles would the best place to start for those who wish to avoid or minimise the pestilence.
(My father's book can be ordered from http://hillsidebooks.com/ and I will write a more direct review of it here soon)