We examined data from 75 infestations of the Mediterranean fruit fly (Medfly) and 286 of the Queensland fruit fly (Qfly) that have occurred in quarantined and normally fly-free zones in Australia from 1974 to 2000. The radius of occurrence of both adult male flies and infested fruit was almost always less than 1 km. The rare cases where there was an isolated occurrence beyond 1 km of an epicentre were most likely due to (and can be treated as) separate introductions. Our analysis shows that effective quarantine radii for suspension of fly-free status should be related to the number of flies trapped around the epicentre and the density of the trap array (if the appropriate code of practice is applied). Most detections of fruit flies involve the trapping of very few flies and 18% of Medfly infestations and 71% of Qfly infestations that are detected are not classified as outbreaks and are left to die out without any treatment. For each species, we have used 3 alternative methods to calculate confidence limits for infestation radii. The upper limits could also serve as quarantine radii. These limits increase with the rate of trapping of male flies and have a theoretical probability of 3/100 000 (i.e. probit 9) of being exceeded. The quarantine radii for most declared outbreaks, when calculated with any of our methods, would be small because the number of flies detected is usually only just above the threshold for such a declaration. If our methods were used for beneficial species or for re-introductions of endangered species, the lower confidence limits could be used to calculate the size of inoculum required for a high probability of initial establishment.

Seven small unquarantined towns in the central western district of New South Wales were used to compare variants of the sterile insect technique with respect to their suitability for suppression of populations of the Queensland fruit fly, Bactrocera tryoni (Froggatt). Two towns were treated with weekly releases of immature sterile flies at rates varying from 48 000 to 115 000 sterile males per km2. Evidence for suppression was poor (from comparison with 2� untreated towns) and the ratio of sterile to wild flies caught in monitoring traps never exceeded 80 : 1 in the last 4�weeks of any season or 40 : 1 during other parts of any season. However, the recapture rates of the sterile flies and estimates of their survival rates were often as good as the best that have been reported previously. Two other towns were treated with weekly releases of mature flies at rates of 5000–12 000 sterile males per km2. The recapture rates and estimates of survival rates of flies released when mature were unexpectedly low and the ratios of sterile to wild flies were often less than 1 : 1 and never exceeded 12 : 1. The results are discussed in terms of the relatively harsh climate of these towns (located in a region of average annual rainfall of 450–600 mm) and lack of quarantine.

Atopy to the fungus Alternaria is strongly associated with respiratory disease. The prevalences of asthma and of allergy to Alternaria are high amongst children living in rural towns of southeastern Australia. In such towns, airborne allergenic spores have been proposed to arise from nearby crops, but this has not been tested and crops are unlikely to be the only sources of Alternaria. We sought to identify sources and factors that in¯uence concentrations of spores of Alternaria detected in rural towns. Over two years, we sampled spores in two towns (Wagga Wagga and Moree, New South Wales, Australia), in nearby wheat and cotton crops during harvesting and control periods, in a cotton gin and a grain shed. Alternaria was present in both towns throughout the study, and above the crops, at the gin and grain shed. Daily and annual concentrations were amongst the highest recorded worldwide and peaks persisted for six months in Wagga Wagga and ten months in Moree. Crop maturation aVected the spore load in the air more than the actual days of harvest. Regression analysis showed that the overall spore concentrations above towns correlated with those above crops. Variables of rainfall and maximum temperature correlated with concentrations in both towns, and additionally wind direction in Wagga Wagga. In conclusion, crops and produce handling released spores into the air that reached nearby rural towns, with peaks in spore concentrations following warm temperatures and recent rainfall.

The study was conducted to characterise the underlying resistance mechanisms responsible for high levels of pyrethroid resistance in Frankliniella occidentalis (Pergande) in Australia. Seven commercially available pyrethroids (acrinathrin, alpha-cypermethrin, bifenthrin, deltamethrin, esfenvalerate, permethrin and tau-fluvalinate) were evaluated against seven F. occidentalis strains collected from ornamentals, fruit and vegetables in three states of Australia. A Potter spray tower was used to test for pyrethroid resistance and all field strains were found to be resistant, with resistance ratios ranging from 15-fold deltamethrin to 1300-fold tau-fluvalinate. The two most resistant strains were further tested for detoxification enzymes that could be involved in resistance. Three synergists, piperonyl butoxide (PBO), diethyl maleate (DEM) and profenofos, which, respectively, inhibit the enzymes cytochrome P-450 monooxygenases, glutathione S-transferases and esterases, were used. The synergism data indicate that multiple mechanisms may be involved in pyrethroid resistance in Australian populations of F. occidentalis. Among the three synergists, PBO considerably reduced pyrethroid resistance in the selected strains compared with DEM and profenofos. The practical implication for PBO use to suppress pyrethroid resistance in F. occidentalis is elaborated.

An experiment to determine the efficacy of sprays containing polysaccharides (0.025-0.2 g/L water) and/or petroleum spray oil (1.25-10 mL/L water) for control of citrus leafminer, Phyllocnistis citrella, unequivocally demonstrated that oil sprays suppress the number of mines/leaf. Oil concentrations 2 2 . 5 mL/L of water were effective, but the polysaccharides had no effect. We recommend sprays containing 2.5-5 mL oil/L. of water. The results are discussed in relation to their perceived importance in citrus integrated pest management programs and historical recommendations for the use of oils to control the pest.