Box 6.3. Climatic modeling for fruit flies
The Queensland fruit fly, Bactrocera tryoni, is a pest of most commercial fruits. The females oviposit into the fruit and larval feeding followed by rotting quickly destroys it. Even if damage in an orchard is insignificant, any infestation is serious because of restrictions on interstate and overseas marketing of fruit-fly-infested fruit.
CLIMEX has been used by R.W. Sutherst and G.F. Maywald to describe the response of B. tryoni to Australia’s climate. The growth and stress indices of CLIMEX were estimated by inference from maps of the geographical distribution and from estimates of the relative abundance of this fly in different parts of its range in Australia. The map of Australia depicts the ecoclimatic indices (EI) describing the favorableness of each site for permanent colonization by B. tryoni. The area of each circle is proportional to its EI. Crosses indicate that the fly could not permanently colonize the site.
The potential survival of B. tryoni as an immigrant pest in North America can be predicted using CLIMEX by climate-matching with the fly’s native range. Accidental transport of this fly could lead to its establishment at the point of entry or it might be taken to other areas with climates more favorable to its persistence. Should B. tryoni become established in North America, the eastern seaboard from New York to Florida and west to Kansas, Oklahoma, and Texas in the USA, and much of Mexico are most at risk. Canada and most of the central and western USA are unlikely to support permanent colonization. Thus, only certain regions of the continent are at high risk of infestation by B. tryoni and quarantine authorities in those places should maintain appropriate vigilance. (After Sutherst & Maywald 1991.)