Impacts of climate change on high priority fruit fly species in Australia

Tephritid fruit flies are among the most destructive horticultural pests posing risks to Australia’s multi-billion-dollar horticulture industry. Currently, there are 11 pest fruit fly species of economic concern in Australia. Of these, nine are native to this continent (Bactrocera aquilonis, B. bryoniae, B. halfordiae, B. jarvisi, B. kraussi, B. musae, B. neohumeralis, B. tryoni and Zeugodacus cucumis), while B. frauenfeldi and Ceratitis capitata are introduced. To varying degrees these species are costly to Australia’s horticulture through in-farm management, monitoring to demonstrate pest freedom, quarantine and trade restrictions, and crop losses. Here, we used a common species distribution model, Maxent, to assess climate suitability for these 11 species under baseline (1960–1990) and future climate scenarios for Australia. Projections indicate that the Wet Tropics is likely to be vulnerable to all 11 species until at least 2070, with the east coast of Australia also likely to remain vulnerable to multiple species. While the Cape York Peninsula and Northern Territory are projected to have suitable climate for numerous species, extrapolation to novel climates in these areas decreases confidence in model projections. The climate suitability of major horticulture areas currently in eastern Queensland, southern-central New South Wales and southern Victoria to these pests may increase as climate changes. By highlighting areas at risk of pest range expansion in the future our study may guide Australia’s horticulture industry in developing effective monitoring and management strategies

Review of grapes Vitis sp. as an occasional host for Queensland fruit fly Bactrocera. tryoni (Froggatt) (Diptera: Tephritidae)

The recognition of grapes as a host of Queensland fruit fly Bactrocera tryoni (Froggatt) (Qfly) has been inconsistent across Australian states due to the variable nature of reports. Here the current state of knowledge is reviewed. Grapes are not a preferred Qfly host and attacks are infrequent. Infestations were reported to be more common in coastal and subtropical areas or in periods of high rainfall associated with the low availability of preferred hosts. Egg survival appears to be low, although larval survival may be considerably higher. This review has identified a range of literature referring to grapes as a host of Qfly. A review of overseas literature also indicates that grapes are a host for several other fruit fly species.4 page(s

Review of dispersal, survival, and establishment of Bactrocera tryoni (Diptera: Tephritidae) for quarantine purposes

The fruit fly Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) is a species of significant quarantine concern to many countries. Currently, B. tryoni is found in parts of Australia and on some Pacific islands. Understanding dispersal behavior is important for the development of scientifically justified trade restrictions or quarantine distances for B. tryoni. These distances ensure adequate protection for overseas markets while also ensuring that growers sufficiently distant from the affected area are able to retain unrestricted access to markets. This review considers scientific data on dispersal and uses this information to make recommendations for appropriate quarantine distances. Most studies conclude that the lifetime dispersal distance of this species rarely exceeds 1 km, although three studies indicate that longer dispersal distances of a small number of individuals may occasionally occur. These short dispersal distances are consistent with findings for other fruit fly species. Triggers for long-distance dispersal, the fate of these individual flies, nutritional requirements to support this dispersal, and reasons for discrepancies in the dispersal distances reported in different studies are reviewed. Reasons for the inability of B. tryoni to establish along southern parts of the east coast of Australia before European colonization are postulated. A proposed quarantine distance is based on the scientific basis of the mean and 3 SD, with a 3-fold level of protection based on distance. It is proposed that an area contained by a circle with a radius of 1.2 km is a reasonable quarantine area for B. tryoni outbreaks where flies are contained within 200 m of an epicenter. Where total trappings are contained within 400 m of the epicenter, a quarantine distance of 2.4 km is recommended. Three other quarantine distances are proposed based on the formula by using the mean.13 page(s

Review of the past and present distribution of Mediterranean fruit fly (Ceratitis capitata Wiedemann) and Queensland fruit fly (Bactrocera tryoni Froggatt) in Australia

Mediterranean fruit fly (Ceratitis capitata Weidemann, 'Medfly') is currently distributed only in Western Australia. Although occasional detections occur in South Australia and the Northern Territory, they invoke a comprehensive and rapid response to prevent establishment. Medfly previously occurred on the eastern coast of mainland Australia. However, it is believed to have been displaced by Queensland fruit fly (Bactrocera tryoni Froggatt, 'Qfly'), with the last recorded finding of Medfly in 1941 for New South Wales and 1953 in Victoria. Tasmania has not documented any incursions of Medfly since 1920 and the Northern Territory eradicated the last incursion in 1994. In contrast, Qfly is regularly found in parts of Queensland, New South Wales, Victoria, and the Northern Territory. A species closely related to Qfly, B. aquilonis (May), is established in the Northern Territory and northern Western Australia. Occasional detections of Qfly in South Australia and southern Western Australia result in immediate regulatory actions and eradication activities to ensure that it does not become established. South Australia, Tasmania and the Fruit Fly Exclusion Zone are free from fruit flies of economic concern. Any detections of pest fruit fly species in these areas are immediately quarantined and eradicated. The distribution of Qfly has remained largely unchanged for the last half-century, with established populations along the eastern States and the Northern Territory. The Medfly distribution has also remained unchanged for the last half-century. Qfly and Medfly do not currently co-exist in Australia. This is likely because of the differences in egg-laying habits, competition by larvae in fruit and differences in host range. A similar displacement of Ceratitis by Bactrocera has occurred in other parts of the world.12 page(s

Chemical analysis of male annihilation blocks used in the control of Queensland fruit fly Bactrocera tryoni (Froggatt) in New South Wales

The male annihilation technique (MAT) is a chemical control method designed to deplete the males available for mating in a population and thus break the reproductive cycle. In the New South Wales fruit fly control program, caneite has been used as a carrier for the lure and pesticide in MAT blocks for many years. In this paper, MAT blocks containing cuelure as an attractant and malathion as a toxicant were manufactured using two methods, namely bag immersion and roller painting, as part of the control program for Queensland fruit fly in New South Wales between September 1998 and June 2000. These blocks were sampled from storage and the field, along with historical blocks in the field deployed before the current study period. Chemical analyses of these three block types were conducted for malathion, cuelure, and raspberry ketone (a breakdown product of cuelure). There was significantly more cuelure and malathion in blocks made by the bag method than the roller method and in historical blocks. The bag method resulted in chemical concentrations closer to the desired standards. There were no significant differences between the three methods in block weight or in level of raspberry ketone. Cuelure levels declined more quickly than malathion although both chemicals were found in all blocks. For the analysis within samples, there were few significant correlations between raspberry ketone and other parameters, but there were many significant correlations between cuelure, malathion and the block weight.5 page(s

The Rise and demise of control options for fruit fly in Australia

For several decades, control of fruit fly pests in Australia has depended to a large degree on dimethoate, a broad-spectrum organophosphate insecticide that has been widely used on many different crops as well as on ornamental plants. However, many dimethoate use patterns were withdrawn in 2011 following a review by regulatory authorities. This manuscript places dimethoate in context as the latest in a long line of pre-harvest pesticides such as the arsenics, tartar emetic, sodium fluosilicate, nicotine sulphate, the organochlorines, and organophosphates, that have been lost from the fruit fly control toolkit over the past century. The succession of postharvest treatments such as fumigants, dips and sprays is also examined. Dimethoate and fenthion have offered relatively easy and cost effective pest control solutions since the 1960s, but in the absence of equivalent alternatives it is now necessary to develop "systems approaches" based on multiple control strategies and risk assessment. Such approaches represent a fundamental shift in pest management strategy, and will require improved understanding of fruit fly biology to prevent infestation in the field, combined with postharvest surveillance and non-chemical treatments. Some options are briefly discussed.11 page(s

Review of the outbreak threshold for Queensland fruit fly (Bactrocera tryoni Froggatt)

Fruit flies cause losses in horticultural produce across the world and are a major quarantine concern for most countries. Queensland fruit fly (Qfly) is a native to Australia and is also present in a small number of Pacific Island countries. The detection of Qfly in recognized pest free areas triggers quarantine restrictions from domestic and international markets. In Australia, the detection of five male flies has been taken to indicate an outbreak (i.e. unacceptable risk). Matching the domestic standard, many countries have accepted the 5-fly limit as a quarantine threshold. But some other countries have set the detection of two male flies, or even a single fly, as the threshold for an outbreak. This different standard creates an administrative complexity for exporters and trade regulators. In this paper, we review the published science covering the impediments to pest establishment. Outbreak data from Victoria and New South Wales during 2007 and 2009 are reviewed in relation to the 2-fly and 5-fly thresholds. Large volumes of fruit have been traded within Australia and internationally based on the 5-fly threshold without incident and there is no evidence that the 2-fly threshold is more appropriate. While Qfly is recognized as being capable of longer distance dispersal than some other fruit fly species, it is also recognized as a poor colonizer. The 5-fly threshold is proposed as the most appropriate threshold for imposition of quarantine restrictions and is recommended as a universal standard for harmonization of quarantine regulations.7 page(s

Transport from production facility to release locations caused a decline in quality of sterile Queensland fruit fly received for SIT application

Transport from production facility to release locations caused a decline in quality of sterile Queensland fruit fly received for SIT applicatio

Release from a point source and dispersal of sterile Queensland fruit fly (Bactrocera tryoni (froggatt)) (Diptera: Tephritidae) at Wagga Wagga

Fruit flies are a serious pest of horticultural industries throughout the world. The sterile insect technique is used in many countries to suppress or eradicate wild populations. The technique would be more effective if there was a better understanding of the interaction between wild and sterile fruit flies, and their interaction with their environment. We reviewed historic data from the 1998/99 sterile release of Queensland fruit fly (Qfly) at Wagga Wagga, New South Wales which has a resident population of wild Qfly. Sterile flies were released at one point and the wild and sterile numbers were analysed in relation to each other, and to climate and landscape variables. Fifty seven fruit fly traps on a 400 m array within 7 km were used to collect the data. Regression analysis, accounting for 20.1% of the variance, indicated that log number wild Qfly was best predicted by the model with the factors of altitude, growth index, day length, cold stress, rainfall, minimum temperature and dry stress. Log number wild Qfly increased as day length and minimum temperature indices increased but was negatively related to other variables. Regression analysis, accounting for 27.2% of the variance, indicated that log sterile Qfly number was best predicted by a model with parameters including distance from release point, moisture index and maximum temperature. All parameters were inversely related to log number sterile Qfly. Fletcher's inverse distance square rule was tested. The best model linked log number sterile Qfly (including zero detections) with log distance and accounted for 22.5% of the variance. Of the 19 758 sterile Qfly trapped, 50%, 95%, 98% and 100% were trapped within 556 m, 1 355 m, 1 574 m and 5 553 m respectively of the release site. The mean dispersal distance of sterile flies was 830 m and this was used to estimate quarantine distance for wild flies.6 page(s

No Sting in the Tail for Sterile Bisex Queensland Fruit Fly (Bactrocera tryoni Froggatt) Release Programs

Global markets do not tolerate the presence of fruit fly (Tephritidae) in horticultural produce. A key method of control for tephritidae pests, is the sterile insect technique (SIT). Several countries release a bisex strain, i.e., males and females, however the sterile male is the only sex which contributes to wild population declines when released en masse. In commercial orchards, there are concerns that sterile females released as part of bisex strains, may oviposit, i.e., ‘sting’ and cause damage to fruit, rendering it unmarketable. Australia has released a bisex strain of sterile Queensland fruit fly, Bactrocera tryoni Froggatt, for several decades to suppress wild pest populations, particularly in peri-urban and urban environments. Here, we assessed fruit damage in two commercially grown stone fruit orchards where bisex sterile B. tryoni were released, and in an orchard that did not receive sterile flies. The number of detected stings were higher in only one SIT release orchard, compared with the control; however, there was no difference between SIT and control orchards in the number of larvae detected. We showed that there is no evidence that sterile female B. tryoni released in large numbers caused stings, or damage that led to downgraded or unsaleable fruit. The bisex strain of sterile B. tryoni is recommended for use in commercial stone-fruit orchards, under the conditions in which this trial was conducted