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The bioclimatic potential of the Queensland fruit fly, Dacus tryoni, in Australia
... An explicit statement to this effect is made by Baker et al. [5]: "The 'dorsalis complex' is one of the most destructive pest species complexes in global fruit production due to polyphagy, invasiveness, high reproductive potential, multivoltinism and continuous activity throughout the year" [our emphasis]. Implicitly it can be seen in models where temperature is the primary driver of population cycles [21][22][23][24], or in population models which seek correlation between fly numbers and environmental variables [25][26][27]. ...
... Meats focused more broadly on how a tropical insect could survive in temperate areas and carried out pioneering research on insect cold acclimation [53][54][55][56][57][58]. As part of his research he developed an early bioclimatic model for Qfly, predicting that the species could have between seven to nine generations per year in subtropical and tropical Australia as temperature was rarely limiting [21]. Meats and Fletcher invariably interpreted their results in terms of temperate biology; for example Meats [56,59] and Meats and Fitt [60] discuss Qfly seasonal cold acclimatization in terms of frost tolerance, without asking why a tropical insect should have an evolved mechanism for avoiding frost. ...
... In the southern hemisphere May through August are late autumn/winter months and so the seasonal disappearance of Qfly is not, perhaps, unexpected. However, in tropical Queensland 'winter' is cool only relative to the hot months of the remainder of the year and, as identified by both Meats [21] and Yonow and Sutherst [65], temperature should not be limiting to B. tryoni population growth in the tropics and subtropics even in the winter months, let alone during the summer and early autumn when populations are nevertheless declining. ...
The genus Bactrocera (Diptera: Tephritidae) is endemic to the monsoonal rainforests of South-east Asia and the western Pacific where the larvae breed in ripe, fleshy fruits. While most Bactrocera remain rainforest restricted, species such as Bactrocera dorsalis, Bactrocera zonata and Bactrocera tryoni are internationally significant pests of horticulture, being both highly invasive and highly polyphagous. Almost universally in the literature it is assumed that Bactrocera breed continuously if temperature and hosts are not limiting. However, despite that, these flies show distinct seasonality. If discussed, seasonality is generally attributed to the fruiting of a particular breeding host (almost invariably mango or guava), but the question appears not to have been asked why flies do not breed at other times of the year despite other hosts being available. Focusing initially on B. tryoni, for which more literature is available, we demonstrate that the seasonality exhibited by that species is closely correlated with the seasons of its endemic rainforest environment as recognised by traditional Aboriginal owners. Evidence suggests the presence of a seasonal reproductive arrest which helps the fly survive the first two-thirds of the dry season, when ripe fruits are scarce, followed by a rapid increase in breeding at the end of the dry season as humidity and the availability of ripe fruit increases. This seasonal phenology continues to be expressed in human-modified landscapes and, while suppressed, it also partially expresses in long-term cultures. We subsequently demonstrate that B. dorsalis, across both its endemic and invasive ranges, shows a very similar seasonality although reversed in the northern hemisphere. While high variability in the timing of B. dorsalis population peaks is exhibited across sites, a four-month period when flies are rare in traps (Dec–Mar) is highly consistent, as is the fact that nearly all sites only have one, generally very sharp, population peak per year. While literature to support or deny a reproductive arrest in B. dorsalis is not available, available data is clear that continuous breeding does not occur in this species and that there are seasonal differences in reproductive investment. Throughout the paper we reinforce the point that our argument for a complex reproductive physiology in Bactrocera is based on inductive reasoning and requires specific, hypothesis-testing experiments to confirm or deny, but we do believe there is ample evidence to prioritise such research. If it is found that species in the genus undergo a true reproductive diapause then there are very significant implications for within-field management, market access, and biosecurity risk planning which are discussed. Arguably the most important of these is that insects in diapause have greater stress resistance and cold tolerance, which could explain how tropical Bactrocera species have managed to successfully invade cool temperate regions.
... However, in the last 100 years it has extended its geographic range southward and is currently established in temperate New South Wales and most of Victoria (Fletcher 1979, O'loughlin et al. 1984, Dominiak and Mapson 2017. Bactrocera tryoni is multivoltine (= multiple generations per year), with the annual generation number for a given location thought to be determined by climatic factors, especially temperature (Meats 1981). ...
... Moisture availability is thought to limit the expansion of the fly into inland Australia (Sultana et al. 2017). Based on bio-climatic data, in tropical and subtropical Australia B. tryoni is modelled as being able to have up to eight generations per year (Meats 1981, Yonow & Sutherst 1998), but in areas with a cold winter such as Victoria, only three to four generations are thought possible in a year (Fletcher 1979(Fletcher , O'loughlin et al. 1984. In temperate Australia sexual activities of adult flies cease during late autumn and they remain inactive until spring, the breeding cessation traditionally correlated with cold winter temperatures (Bateman 1968, Fletcher 1975, Fletcher 1979. ...
... Unlike temperate regions, in the tropics temperature fluctuates less during the year and modelling predicts that B. tryoni breeding should be continuous throughout the year if breeding hosts are available (Meats 1981, Sutherst and Yonow 1998, Yonow et al. 2004). Depending on temperature, a predominantly temperature driven CLIMEX model predicted more than six and more potential generations of B. tryoni in tropical and subtropical eastern Australia (Sutherst and Yonow 1998), an almost identical result to the predictions of an earlier B. tryoni phenology model developed by Meats (1981). ...
Queensland fruit fly is a destructive horticultural insect pest. Knowing the age-structure of fly populations, that is the relative proportion of young, middle-age, and old-age flies within a population at a given time, is critical for effective management. The thesis combined behavioural ecology with a novel mathematical analysis to identify the seasonal changes in the age of a wild Queensland fruit fly population. The study showed that the abundance and age-structure of the fly changed predictably with the season, strongly suggestive of an endogenous mechanism that helps the fly cope with seasonal changes in resource availability.
... Prior to European settlement of Australia, the Queensland fruit fly was considered endemic to the tropical and subtropical rainforests of north-eastern Australia (Meats 1981;Reynolds and Orchard 2015). It has subsequently spread from this habitat and is now considered endemic in most of east-coast mainland Australia, including temperate areas, except where under regulatory control (Dominiak and Daniels 2012). ...
... It has subsequently spread from this habitat and is now considered endemic in most of east-coast mainland Australia, including temperate areas, except where under regulatory control (Dominiak and Daniels 2012). In Queensland, B. tryoni occurs in high numbers year-round with 3-4 generations per year in the southern areas (Meats 1981). Meats (1981) believed that populations in temperate regions were transient, due to populations immigrating in each season but not establishing year-round. ...
... In Queensland, B. tryoni occurs in high numbers year-round with 3-4 generations per year in the southern areas (Meats 1981). Meats (1981) believed that populations in temperate regions were transient, due to populations immigrating in each season but not establishing year-round. However, there is now clear evidence that the fly is permanently established in temperate eastern Australia (Dominiak and Daniels 2012;Reynolds and Orchard 2015;Agriculture Victoria 2017;Dominiak and Mapson 2017). ...
... Building on earlier microsatellite and mitochondrial studies of the species (Gilchrist et al. 2004;Gilchrist and Meats 2010;Blacket et al. 2017), we here apply a genome-wide marker approach based on reduced representation resequencing to a major insect pest of Australian horticulture, the Queensland fruit fly (Qfly) Bactrocera tryoni (Clarke et al. 2011;Dominiak and Mapson 2017;Sultana et al. 2017). This highly polyphagous species has expanded its distribution from its native tropical/subtropical range in coastal Queensland (QLD) and northern New South Wales (NSW) southwards into more temperate regions of NSW and Victoria (VIC), westwards into the Northern Territory (NT) and northern Western Australia (nWA), where hybridisation with a closely related taxon, the Northern Territory fruit fly B. aquilonis (NTfly), has led to some bidirectional gene flow, and eastwards into several Melanesian countries (Froggatt 1909;May 1965;Meats 1981;Osborne et al. 1997;Popa-Báez et al. 2020). Much of this expansion is attributed to the extension of suitable habitat with increasing horticulture post-European settlement (Dominiak and Mapson 2017). ...
... Moreover, further incursions are ongoing into the now disestablished Fruit Fly Exclusion Zone (FFEZ) in the Riverina region of NSW and VIC (Dominiak and Mapson 2017;Dominiak 2019). Of particular concern now are repeated incursions into New Zealand (NZ) and South Australia (SA) and the first ever incursions into Tasmania (TAS), although permanent populations apparently have not to date established in these territories (Meats 1981;Yonow et al. 2004;Aguilar et al. 2015;Sultana et al. 2017). ...
... Although occasional reports of Qfly in imported bananas and mangoes date back to the late nineteenth century, the only confirmed report of a 'breeding incursion' till this point actually involved the Mediterranean fruit fly Ceratitis capitata (Lea 1899, Lea 1908). The marginal bioclimatic suitability for Qfly in Tasmania would certainly hinder its long-term establishment in the state (Meats 1981), although future climatic scenarios might not be so restrictive (Sultana et al. 2017(Sultana et al. , 2019. ...
Incursions of the Queensland fruit fly Bactrocera tryoni (Qfly) into areas without permanent Qfly populations present serious threats to the Australian and New Zealand horticultural industries. Identifying the origins of recent incursions will help reduce future threats by enabling the targeting of problematic incursion routes for more stringent quarantine protocols. Here we present an analytical framework based on supervised and unsupervised machine learning to identify the origins and recent population history of incursion individuals. Our framework is based on a recently developed reference dataset of genome-wide markers for 35 Qfly populations from across the ranges of Qfly and the related taxon Bactrocera aquilonis (NTfly). We apply our framework to recent incursions into New Zealand, Tasmania and South Australia. Two distinct Qfly sources were identified for incursions into New Zealand (total 18 individuals), one from the east coast of Australia and one from New Caledonia. All eight recent incursion collections analysed (total 85 individuals) from South Australia and Tasmania most likely originated from just one of six clusters of populations in our reference database, Qfly from the east coast of Australia. None were found to originate from clusters containing NTfly or Qfly/NTfly hybrids in the Northern Territory or north Western Australia. Several, but not all, of the collections showed signals of small founding population size and two Tasmanian collections each included individuals apparently derived from three different sources within the east coast of Australia. In total, several more incursion events were detected than previously known, although some were founded by relatively few individuals.
... In Qfly, survival and reproduction are heavily influenced by temperature, moisture and availability of suitable host fruits [31][32][33][34][35], and Fletcher [36,37] has suggested that the populations now persisting in the temperate regions do so in part by short distance movements between orchards and nearby water sources. Desiccation stress is therefore speculated to be a major determinant of Qfly distributions [32,35,38], although there is as yet no empirical data in the literature about variation in desiccation resistance amongst wild populations of the species. ...
... In Qfly, survival and reproduction are heavily influenced by temperature, moisture and availability of suitable host fruits [31][32][33][34][35], and Fletcher [36,37] has suggested that the populations now persisting in the temperate regions do so in part by short distance movements between orchards and nearby water sources. Desiccation stress is therefore speculated to be a major determinant of Qfly distributions [32,35,38], although there is as yet no empirical data in the literature about variation in desiccation resistance amongst wild populations of the species. Not much is known about variation in Qfly thermal resistance either. ...
... However, he acknowledged some possible bias in his work through the inclusion of what is now recognised as a sibling species, B. neohumeralis (which he termed 'variety neohumeralis'), in some of his collections. Furthermore, Meats [32] found no difference in cold resistance between northern and southern Qfly collections and he later reported rapid acclimation to low temperatures in several populations in the laboratory. Overall the current literature on geographic variation in the climatic stress resistances of Qfly is fragmentary and provides insufficient detail for understanding the role of such variation in the ecology and invasive potential of the species, and some of the literature is not based on current taxonomy [6,38]. ...
Background
The highly polyphagous Queensland fruit fly ( Bactrocera tryoni Froggatt) expanded its range substantially during the twentieth century and is now the most economically important insect pest of Australian horticulture, prompting intensive efforts to develop a Sterile Insect Technique (SIT) control program. Using a “common garden” approach, we have screened for natural genetic variation in key environmental fitness traits among populations from across the geographic range of this species and monitored changes in those traits induced during domestication.
Results
Significant variation was detected between the populations for heat, desiccation and starvation resistance and wing length (as a measure of body size). Desiccation resistance was correlated with both starvation resistance and wing length. Bioassay data for three resampled populations indicate that much of the variation in desiccation resistance reflects persistent, inherited differences among the populations. No latitudinal cline was detected for any of the traits and only weak correlations were found with climatic variables for heat resistance and wing length. All three stress resistance phenotypes and wing length changed significantly in certain populations with ongoing domestication but there was also a strong population by domestication interaction effect for each trait.
Conclusions
Ecotypic variation in heat, starvation and desiccation resistance was detected in Australian Qfly populations, and these stress resistances diminished rapidly during domestication. Our results indicate a need to select source populations for SIT strains which have relatively high climatic stress resistance and to minimise loss of that resistance during domestication.
... The Queensland fruit fly (QFF) Bactrocera (Dacus) tryoni (Froggatt) (Diptera: Dacineae), is one of Australia's most economically important horticultural pests. It is a tropical to sub-tropical species, with a wide host range (Fletcher, 1987a(Fletcher, , 1989Meats, 1981). There has been an increasing incidence of outbreaks of QFF in the more temperate, economically valuable horticultural areas, such as the Murrumbidgee Irrigation Area, Sunraysia and Adelaide since 1987 (Horticultural Policy Council, 1991). ...
... Whilst the population dynamics of the olive fruit fly, Dacus oleae have been modelled to some extent (Comins and Fletcher, 1988;Fletcher and Comins, 1985), previous models of QFF have only addressed its geographical distribution (Meats, 1981;Yonow and Sutherst, 1998). Due to the pest status of this species a great deal of research has been undertaken into aspects of the biology and ecology of QFF with a view to improving its management. ...
... The development rate of eggs (E d ) is estimated from published data for temperatures up to 33 • C (Bateman, 1967;Fitt, 1984Fitt, , 1990aMeats, 1981;Myers, 1952;Pritchard, 1978): ...
... Although it generally has been accepted that the southernmost limit of QFF distribution is in East Gippsland (e.g. May 1963;Bateman 1967;Meats 1981), and M. Campbell and D. Maelzer (pers. comm.) ...
... comm.) believe that Melbourne is too cold for permanent populations, it would appear that Melbourne can support perma- Bateman (1967); (c) Gibbs (1967); (d ) Meats (1981); (e) Drew et al . (1982); and (f ) Fletcher and Bateman (1983). ...
... comm.). In his bioclimatic analysis of QFF, Meats (1981) concludes that B. tryoni could spread across tropical regions of northern Australia and achieve serious pest status in the northern part of the Northern Territory and in northern Western Australia. ...
CLIMEX is used to analyse the potential distribution of the Queensland fruit fly in relation to long-term average meteorological data. Different hypotheses on the mechanisms limiting the distribution of this species are examined. The analyses indicate that different CLIMEX models discriminate between locations in different ways. In particular, the models describing the limiting effects of cold stress yield substantially different estimates of the areas that can support overwintering populations. With the threshold temperature model of cold stress, extreme low temperatures exclude flies from high-altitude areas, but fail to exclude them from areas known not to support overwintering populations. These areas can only be rendered unfavourable by using the degree-day model of cold stress, which prevents sufficient thermal accumulation above the developmental threshold to maintain basic metabolic processes for long periods. In contrast, 2 models describing different modes of heat stress accumulation provide similar results and are interchangeable. Our analyses also indicate the potential for agricultural practices, such as irrigation, to alter quite dramatically the suitability of an area for Queensland fruit fly, and impact upon its geographical distribution and the pattern of activity.
... One of the years of the latter study had many severe frosts, yet some flies survived until the spring hosts were available. Using different techniques, Meats (1981) and Yonow and Sutherst (1998) have independently explained the southern limit to the distribution of B. tryoni in terms cold tolerance of adults (important only at higher altitudes) and the number of 'day degrees' in a year required to complete at least two generations (important at lower altitudes). Likewise, both of the above publications conclude that spread to the drier inland is limited to a large extent by inadequate rainfall. ...
... Small cohorts were reared in either a warm (25-28°C) or cool (18 ± 0.5°C) regime. The cohorts were started simultaneously with approximately 100 eggs each (0-4 h old), there being 12 (May 1963;Meats 1981;Drew 1982). Bactrocera neohumeralis also occurs at Weipa and other settlements on the west coast of Cape York (Drew 1982;Osborne et al. 1997). ...
... The survival schedules in midwinter were similar to those observed at the same time of year by Fletcher (1979) in an open population of B. tryoni and by O'Loughlin et al. (1984) in a caged one. The reproductive potential of the field cohorts of B. neohumeralis in the present study suggests that the species is capable of bridging the 'breeding gap' (Meats 1981) that is imposed on B. tryoni by winters having extended periods when the daily maximum temperatures are below 20°C. The lower fecundity of B. neohumeralis was consistent with the unpublished observation that it was always lower than that of B. tryoni in the relatively mild conditions of normal culture (25-28°C) and in experimental regimes at 18°C. ...
Abstract The geographical range of Bactrocera neohumeralis does not extend as far south as that of its sibling species, B. tryoni. However, there was no evidence of any difference between the two species in terms of physiological limitation to southerly spread when comparisons were made of low temperature torpor thresholds of adults, survival time of adults at −4°C and development rates of all stages in either warm or cool regimes. The survival schedule of the two species was similar in the laboratory and also in the moderately cold conditions experienced by caged cohorts that were exposed to winter field temperatures between late April and early November at Richmond, New South Wales (500 km south of the usual southerly limit of B. neohumeralis). Overwintered cohorts of both species laid similar numbers of eggs in September in terms of eggs per emerged female (an indicator of the reproductive potential). However, because the proportion of B. tryoni surviving to the period of 1–15 September was less than half that for B. neohumeralis, the production per surviving female was more than double in B. tryoni. The possibility of the southerly spread of B. neohumeralis being limited by an Allee effect is discussed.
... Queensland fruit fly is widespread in eastern Australia, as well as being invasive in New Caledonia, French Polynesia, Pitcairn Islands and Cook Islands (http://www.spc.int/Pacifly/). Originally considered endemic to patches of tropical and subtropical rainforests extending along the east coast from Cape York to southern NSW (Meats, 1981), the development of commercial fruit production in Australia has promoted range expansion into more temperate and drier areas (May, 1961a). Bactrocera tryoni were first reported in the Sydney region in the late 1800s (May, 1961a) and now have a permanent range extending inland into central Queensland and New South Wales as well as in Alice Springs and Darwin (Osborne et al., 1997), and possibly more widely throughout the Northern Territory and northern Western Australia depending on the species status of B. aquilonis (see discussion above). ...
... Sporadic outbreaks occur in Victoria and South Australia (May, 1963;Maelzer, 1990a,b;Maelzer et al., 2004;Meats et al., 2006), and a single outbreak was detected in 1989 and then successfully eradicated from Perth, Western Australia (Ayling, 1989;Fisher, 1996). However, these parts of Australia usually remain free of B. tryoni because of isolation from the permanent distribution range of the fly by intervening regions with unsuitable conditions (Meats, 1981;Yonow & Sutherst, 1998). ...
... The three factors considered to determine the suitability of a region for B. tryoni survival and reproduction are temperature, moisture and availability of suitable larval host fruits (May, 1963;Meats, 1981;Yonow & Sutherst, 1998). The influence of temperature on the survival and reproduction of Queensland fruit fly has been extensively Ann Appl Biol 158 (2011) 26-54 © 2010 The Authors studied and is reviewed elsewhere (Meats, 1989a). ...
The distribution, systematics and ecology of Bactrocera tryoni, the Queensland fruit fly, are reviewed. Bactrocera tryoni is a member of the B. tryoni complex of species, which currently includes four named species, viz. B. tryoni ssp., B. neohumeralis, B. melas and B. aquilonis. The species status of B. melas and B. aquilonis is unclear (they may be junior synonyms of B. tryoni) and their validity, or otherwise, needs to be confirmed as a matter of urgency. While Queensland fruit fly is regarded as a tropical species, it cannot be assumed that its distribution will spread further south under climate change scenarios. Increasing aridity and hot dry summers, as well as more complex, indirect interactions resulting from elevated CO2, make predicting the future distribution and abundance of B. tryoni difficult. The ecology of B. tryoni is reviewed with respect to current control approaches (with the exception of sterile insect technique (SIT) which is covered in a companion paper). We conclude that there are major gaps in the knowledge required to implement most noninsecticide-based management approaches. Priority areas for future research include host–plant interactions, protein and cue-lure foraging and use, spatial dynamics, development of new monitoring tools, investigating the use of natural enemies and better integration of fruit flies into general horticultural IPM systems.
... While the decline in temperate areas is thought to be caused by low winter temperatures (Yonow & Sutherst, 1998;Yonow et al., 2004), the primary driver proposed for population declines in the tropics is the absence of host fruits (Muthuthantri et al., 2010 We found that qualitatively, model predictions (and its literature basis) matched our empirical findings: (a) females continued egg laying as daily maxima exceeded the female activity threshold of 18°C (Bateman, 1967) and mean temperatures above 13.5°C allowed for ovarian maturation (Muthuthantri et al., 2010;Pritchard, 1970;Yonow et al., 2004); (b) juvenile stages successfully developed and produced next generation flies but until mid-August contributed few individuals only; (c) development times in the field were prolonged because of lower temperatures (Bateman, 1967;Meats, 1981;Myers, 1952;O'Loughlin, 1975;Sonleitner & Bateman, 1963;Yonow et al., 2004); and (d) flies were subjected to increased mortality rates in the field versus the laboratory (Bateman, 1967;Meats, 1984Meats, , 1981Myers, 1952;O'Loughlin, 1975;Sonleitner & Bateman, 1963;Yonow et al., 2004). The number of flies emerging in the field peaked in late August/early September, which supports the hypothesis that in subtropical regions the F1 generation of overwintering females may significantly contribute to the pronounced spring peak in fly abundance (Muthuthantri et al., 2010). ...
... While the decline in temperate areas is thought to be caused by low winter temperatures (Yonow & Sutherst, 1998;Yonow et al., 2004), the primary driver proposed for population declines in the tropics is the absence of host fruits (Muthuthantri et al., 2010 We found that qualitatively, model predictions (and its literature basis) matched our empirical findings: (a) females continued egg laying as daily maxima exceeded the female activity threshold of 18°C (Bateman, 1967) and mean temperatures above 13.5°C allowed for ovarian maturation (Muthuthantri et al., 2010;Pritchard, 1970;Yonow et al., 2004); (b) juvenile stages successfully developed and produced next generation flies but until mid-August contributed few individuals only; (c) development times in the field were prolonged because of lower temperatures (Bateman, 1967;Meats, 1981;Myers, 1952;O'Loughlin, 1975;Sonleitner & Bateman, 1963;Yonow et al., 2004); and (d) flies were subjected to increased mortality rates in the field versus the laboratory (Bateman, 1967;Meats, 1984Meats, , 1981Myers, 1952;O'Loughlin, 1975;Sonleitner & Bateman, 1963;Yonow et al., 2004). The number of flies emerging in the field peaked in late August/early September, which supports the hypothesis that in subtropical regions the F1 generation of overwintering females may significantly contribute to the pronounced spring peak in fly abundance (Muthuthantri et al., 2010). ...
Around the world, several pest tephritids are extending their ranges from warm tropical or Mediterranean climates into cooler temperate regions. The ability to tolerate climatic diversity is uncommon among insects, and understanding the population phenology drivers of such species across different parts of their range will be critical for their management. Here, we determined the role of temperature versus fruit availability on the population phenology of Queensland fruit fly, Bactrocera tryoni. Using a field site located at the subtropical/temperate interface, with host fruits continuously available, we monitored the development times and abundance of B. tryoni, a species which has invaded temperate Australia from the tropics. From fruit samples held at ambient and controlled conditions, the abundance of emerging flies was highly variable among collection dates, but the variance did not reflect the observed changes in temperature. For most samples, the survival rate of flies in a field site was lower than predicted by a day‐degree population model fitted with mean daily field temperatures. The development time of the immature stage in the field was prolonged, presumably due to cooler ambient conditions, but the fitted day‐degree population model consistently over‐predicted estimated development times. Our results indicate that at the subtropical/temperate interface, the decline in B. tryoni populations during winter is only partly driven by temperature and host availability. We classify B. tryoni as a climate generalist, which likely employs physiological as well as behavioural mechanisms to achieve broad climatic tolerance ranges.
... The climate and the distribution of towns, orchards and other crops would assist such a strategy. The natural climate of the FFEZ and adjacent country (now designated the risk reduction zone, RRZ) is only marginally favourable to the fruit fly, mainly because of low natural rainfall (Meats 1981;Yonow and Sutherst 1998;Dominiak et al. 2000). The FFEZ is only favourable because both the towns and the production areas are irrigated, whereas in the surrounding country only the towns are irrigated, leaving us with small 'virtual island' populations to deal with (Dominiak et al. 2000). ...
... The chief climatic influence on fruit-fly populations over most of their range in summer is rainfall (Bateman 1968;Meats 1981). The effect of rainfall can, however, be offset by evaporation, so the dry-stress index of Yonow and Sutherst (1998) is perhaps more appropriate, especially for the inland regions. ...
Abstract: Data from extended field-cage studies are use to compare the performance of differently acclimated sterile flies against cold-hardy target flies in terms of differential rates of survival and mating competitiveness in cold spring weather.
... The population phenologies thus generated represent the perceived influence of climate. Using climate to generate Q-fly phenologies is a valid assumption, at least for temperate parts of Australia, as temperature and rainfall are considered to drive the system in these regions (Bateman, 1968; Meats, 1981; O'Loughlin et al., 1984). Model validation runs by Yonow et al., using data from three temperate sites and regressing observed data against predicted data, produced significant R² values of 0.16, 0.27 and 0.37 (df=, respectively, 85, 60 and 114). ...
... Previous studies have predicted that up to 15 generations per year of B. tryoni could potentially occur in northern parts of the fly's range (Meats, 1981; Yonow & Sutherst, 1998). These predictions have, however, been almost exclusively based on research undertaken in temperature Australia and assume abiotic conditions (particularly temperature) are the drivers of Q-fly population dynamics in all parts of its range. ...
Bactrocera tryoni is a polyphagous fruit fly, originally endemic to tropical and subtropical coastal eastern Australia, but now also widely distributed in temperate eastern Australia. In temperate parts of its range, B. tryoni populations show distinct seasonal peaks driven by changing seasonal climates, especially changing temperature. In contrast to temperate areas, the seasonal phenology of B. tryoni in subtropical and tropical parts of its range is poorly documented and the role of climate unknown. Using a large, historical (1940s and 1950s) fruit fly trapping dataset, we present the seasonal phenology of B. tryoni at nine sites across Queensland for multiple (two to seven) years per site. We correlate monthly trap data for each site with monthly weather averages (temperature, rainfall and relative humidity) to investigate climatic influences. We also correlate observed population data with predicted population data generated by an existing B. tryoni population model. Supporting predictions from climate driven models, B. tryoni did show year-round breeding at most Queensland sites. However, contrary to predictions, there was a common pattern of a significant population decline in autumn and winter, followed by a rapid population increase in August and then one or more distinct peaks of abundance in spring and summer. Mean monthly fly abundance was significantly different across sites, but was not correlated with altitudinal, latitudinal or longitudinal gradients. There were very few significant correlations between monthly fly population size and weather variables (either for the corresponding month or for up to 3 months previously) for eight of the nine sites. For the southern site of Gatton fly population abundance was correlated with temperature. Results suggest that although climate factors may be influencing patterns of B. tryoni population abundance in southern subtropical Queensland, they are not explaining patterns of abundance in northern subtropical and tropical Queensland. In the discussion we focus on the role of other factors, particularly larval host plant availability, as likely drivers of B. tryoni abundance in tropical and subtropical parts of its range.
... The pre-oviposition period of Bactrocera dorsalis was 18-22 days (Saeki et al., 1980;Meats, 1981;Qureshi et al., 1993;Shivyya et al., 2007;Shehata, 2008 Kalia andYadav, 2015 while it was 7 to 13 days on mango (Kumar and Agrawal, 2005).While studying the impact of varieties, reported that the pre-oviposition period was lowest (9.0 days) on Dashehari as against 12.66 days on Mallika as well as Bangalora and 17.33 days on Amrapali. However, in guava this period was shorter on Lucknow-49 (12 days) in comparison to Allahabadi Safeda (13.33 days). ...
Fruit flies (Diptera: Tephritidae) are among the most economically
important pest species in the world, attacking a wide range of fruits and fleshy
vegetables throughout tropical and sub-tropical regions in the world. They
have attained the status of quarantine insect pest worldwide. The damaging
stage of fruit fly is the larvae which remains unexposed to the pesticides to be
applied for their management. It pupates in the soil so that it stays away from
the exposure of natural enemies. Moreover, it is multivoltine in nature and
completes seven to nine generations in the tropical region due to the
continuous availability of food source. There is the necessity of
implementation of sterile insect technique for the management of fruit flies.
Complete knowledge about the biology of the fruit flies help in successful
implementation of the autocidal technique.
... Australia hosts over 300 tephritid fruit fly species, with several species of Bactrocera (Tephritidae: Dacini), and in particular, Queensland fruit fly, Bactrocera tryoni, as the economically most significant (Meats, 1981;Drew, 1989;Hancock et al., 2000;Dominiak and Daniels, 2012). Wolbachia gene sequences have previously been detected in male individuals of 9 out of 24 tested Australian tephritid fruit fly species (Morrow et al., 2014(Morrow et al., , 2015. ...
Wolbachia are widespread endosymbionts that affect arthropod reproduction and fitness. Mostly maternally inherited, Wolbachia are occasionally transferred horizontally. Previously, two Wolbachia strains were reported at low prevalence and titres across seven Australian tephritid species, possibly indicative of frequent horizontal transfer. Here, we performed whole‐genome sequencing of field‐caught Wolbachia‐positive flies. Unexpectedly, we found complete mitogenomes of an endoparasitic strepsipteran, Dipterophagus daci, suggesting that Wolbachia in the flies are linked to concealed parasitisation. We performed the first genetic characterisation and detected D. daci in Wolbachia‐positive flies not visibly parasitised, but most Wolbachia‐negative flies were D. daci‐negative, presumably reflecting polymorphism for the Wolbachia infections in D. daci. We dissected D. daci from stylopised flies and confirmed that Wolbachia infects D. daci, but also found Wolbachia in stylopised fly tissues, likely somatic, horizontally transferred, non‐heritable infections. Furthermore, no Wolbachia cif and wmk genes were detected, and very low mitogenomic variation in D. daci across its distribution. Therefore, Wolbachia may influence host fitness without reproductive manipulation. Our study of 13 tephritid species highlights that concealed early stages of strepsipteran parasitisation led to the previous incorrect assignment of Wolbachia co‐infections to tephritid species, obscuring ecological studies of this common endosymbiont and its horizontal transmission by parasitoids. This article is protected by copyright. All rights reserved.
... Wild B. tryoni have previously been found to survive longer than mass-reared B. tryoni under desiccation stress 49 , and this is consistent with the differences in microhabitat preferences observed in the present study. Broader dispersal and survival of wild B. tryoni over large areas can be strongly influenced by temperature, rainfall, and relative humidity [87][88][89][90][91] . Also, Dominiak et al. 92 notes that wild B. tryoni survive best in tropical and urban habitats due to greater availability of water and humid microclimates. ...
Insects tend to live within well-defined habitats, and at smaller scales can have distinct microhabitat preferences. These preferences are important, but often overlooked, in applications of the sterile insect technique. Different microhabitat preferences of sterile and wild insects may reflect differences in environmental tolerance and may lead to spatial separation in the field, both of which may reduce the control program efficiency. In this study, we compared the diurnal microhabitat distributions of mass-reared (fertile and sterile) and wild Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae). Flies were individually tagged and released into field cages containing citrus trees. We recorded their locations in the canopies (height from ground, distance from canopy center), behavior (resting, grooming, walking, feeding), and the abiotic conditions on occupied leaves (temperature, humidity, light intensity) throughout the day. Flies from all groups moved lower in the canopy when temperature and light intensity were high, and humidity was low; lower canopy regions provided shelter from these conditions. Fertile and sterile mass-reared flies of both sexes were generally lower in the canopies than wild flies. Flies generally fed from the top sides of leaves that were lower in the canopy, suggesting food sources in these locations. Our observations suggest that mass-reared and wild B. tryoni occupy different locations in tree canopies, which could indicate different tolerances to environmental extremes and may result in spatial separation of sterile and wild flies when assessed at a landscape scale.
... This pattern explains not just our data, but also matches the well documented population phenology of the species, which consistently shows rapid spring increases with populations peaking in late summer and early autumn, before declining again until the following spring 43,44 . The population thus effectively "resets" itself every spring to a single starting generation, rather than having the continuous breeding and overlapping generations predicted by models which assume that temperature and hosts are not limiting for this polyphagous, tropical species 10,15,16 . Further indirect evidence of the endogenous nature of this pattern comes from factory-scale mass rearing data of B. tryoni for the Sterile Insect Technique 61,62 . ...
Bactrocera tryoni is a polyphagous fruit fly that is predicated to have continuous breeding in tropical and subtropical Australia as temperature and hosts are not limiting. Nevertheless, in both rainforest and tropical agricultural systems, the fly shows a distinct seasonal phenology pattern with an autumn decline and a spring emergence. Temperature based population models have limited predictive capacity for this species and so the driver(s) for the observed phenology patterns are unknown. Using a demographic approach, we studied the age-structure of B. tryoni populations in subtropical Australia in an agricultural system, with a focus on times of the year when marked changes in population abundance occur. We found that the age-structure of the population varied with season: summer and autumn populations were composed of mixed-age flies, while late-winter and early-spring populations were composed of old to very old individuals. When held at a constant temperature, the longevity of adult reference cohorts (obtained from field infested fruits) also showed strong seasonality; the adults of spring and early autumn populations were short-lived, while late autumn and late winter adults were long-lived. While still expressing in modified landscapes, the data strongly suggests that B. tryoni has an endogenous mechanism which would have allowed it to cope with changes in the breeding resources available in its endemic monsoonal rainforest habitat, when fruits would have been abundant in the late spring and summer (wet season), and rare or absent during late autumn and winter (dry season).
... The adults live long, which increases chances of exposure to stressful environmental factors such as moisture, temperature and light (Andrewartha and Birch, 1984). To avoid such stressful conditions, adult flies pursue less stressful microhabitats very hot and moist or light intense environments (Meats, 1981). ...
... The adults live long, which increases chances of exposure to stressful environmental factors such as moisture, temperature and light (Andrewartha and Birch, 1984). To avoid such stressful conditions, adult flies pursue less stressful microhabitats very hot and moist or light intense environments (Meats, 1981). ...
Phytophagous Fruit flies (Diptera: Tephritidae) cause heavy losses on fruits and vegetable crops, and pose a threat to the commercialisation of the horticulture industry in Uganda. In order to develop an effective management strategy against fruit flies, it is important to understand the diversity, patterns of host utilization and ecological niche of the major fruit species, which were the objectives of this study. Major differences in species richness and community structure occurred among the three major mango growing regions. The alien Bactrocera invadens was noted to be displacing native fruit fly species. Similarly, fruit infestation was predominated by B.invadens, while damage by native fruit flies was negligible. Tropical almonds showed the highest fruit fly infestation incidence (87.9%), and were mainly infested by B. invadens (82.1%). Psidium guajava and Mangifera indica were also favorable hosts. There was significant difference in infestation among mango varieties (p < 0.0001). Among the host fruit species, female B. invadens fruit flies frequently oviposited most on fruits that gave better adapted offsprings (support for Preference Performance Hypothesis-PPH), with overall coefficient of determination (R2) for infestation averaging 75.4%. However, PPH was poorly evident among the various mango varieties, with the trends suggestive of an Optimal Foraging Theory (OFT)
(oviposition on readily available fruits). B. invadens from different agro ecological zones and fruit hosts were significantly different in morphology (p < 0.0001), which suggested that geographic and host-associated adaptations could produce phenotypic variations that can lead to ecotype and host populations. Precipitation (61.41%) and temperature (29.21%) were the most important determinants of fruit fly distribution in the country. On that basis, the most suitable habitats were central and mid north zones, while the western, north-eastern areas were marginal. Future potential fruit fly habitats were projected to decline by 25.4% on average. Dacus bivittatus, Bactrocera cucurbitae and Ceratitis anonae were projected to be the least climate change resilient species. D. cilliatus (249.3%), B. invadens (-1.9%) and C. cosyra (-2.2%) were projected to be the most climate change resilient species. Future fruit fly niches were predicted to shift northwards, mainly to the northern moist farmlands. This study has provided knowledge
on several aspects of the ecology of fruit and crucial information that can help in the
development of adaptative pest management strategies in Uganda.
... For instance, Muthuthantri et al. 43 reported that many subtropical sites in Queensland are marginal for Qfly breeding and general activity in winter. Similarly, the southern extent of Qfly is limited by winter temperature 3 . In Melbourne, Qfly pupae do not generally survive winter months 2 . ...
Anthropogenic climate change is a major factor driving shifts in the distributions of pests and invasive species. The Queensland fruit fly, Bactrocera tryoni Froggatt (Qfly), is the most economically damaging insect pest of Australia’s horticultural industry, and its management is a key priority for plant protection and biosecurity. Identifying the extent to which climate change may alter the distribution of suitable habitat for Qfly is important for the development and continuation of effective monitoring programs, phytosanitary measures, and management strategies. We used Maxent, a species distribution model, to map suitable habitat for Qfly under current climate, and six climate scenarios for 2030, 2050 and 2070. Our results highlight that south-western Australia, northern regions of the Northern Territory, eastern Queensland, and much of south-eastern Australia are currently suitable for Qfly. This includes southern Victoria and eastern Tasmania, which are currently free of breeding populations. There is substantial agreement across future climate scenarios that most areas currently suitable will remain so until at least 2070. Our projections provide an initial estimate of the potential exposure of Australia’s horticultural industry to Qfly as climate changes, highlighting the need for long-term vigilance across southern Australia to prevent further range expansion of this species.
... The Queensland fruit fly (Qfly) Bactrocera tryoni is one of the most serious pests of Australian horticulture as it attacks a broad range of fruit crops and many vegetables (Drew et al. 1978;Hancock et al. 2000). Qfly was originally distributed in coastal Queensland and possibly northern New South Wales, but it is now widely established in Australia's east coast and far inland (Meats 1981;Gilchrist et al. 2006). The past and present distribution of Qfly was reviewed by Dominiak and Daniels (2012). ...
The sterile insect technique (SIT) has been used to suppress or eradicate fruit flies. It is critical to be able to identify sterile and wild flies so that informed decisions can be made during eradication activities. The current dye marking approach can be flawed on a small number of occasions, and a genetic method is needed to test suspect misidentified samples. As a proof of concept, a single multiplex PCR with nine microsatellite markers was used to study the genetic structure of Queensland fruit flies Bactrocera tryoni (Froggatt) in 11 locations in southern New South Wales. Cluster analysis demonstrated that one cluster was exclusive to the sterile mass-reared flies. A second distinct cluster was exclusive for one site in a wetter cooler area. The other sites were admixture of two main clusters. These nine microsatellite markers could be used to distinguish laboratory-reared flies from field flies. The mass-reared flies would need to be reanalysed after each introduction of wildness.
... Positive and highly significant correlation of Dacus zonatus incidence with minimum and maximum temperature was recorded earlier by Lui and Yeh, (1982). Similar observation were reported by Meats (1981); Drew et al. (1983); Su (1984); Shukla & Prasad (1985); and in India, Agarwal et al. (1999). Also, Woiwod (1997); Bale et al. (2002); Parmesan (2007); and Merrill et al. (2008) stated that changes in climatic conditions could profoundly affect the population dynamics and the status of insect pests of crops. ...
Monitoring of the pest population round the year is one of the most important basic information in formulating IPM concept for sustainable agriculture. The study aimed to investigate the seasonal fluctuation of the adult fly round the year for two successive seasons 2008/2009 and 2009/2010 through the use of cue-lure traps with referring to their affecting by the main weather factors such as temperature (minimum and maximum) and mean relative humidity at Assiut Governorate. Significant variation in occurrence of the pest was recorded during the period of investigation. During warm months the flies were more active as compared to that of cold weather period (December, January, and February) months. Significant positive correlation (r) of fly incidence was noted with maximum and minimum temperature (r = 0.395 and 0.413 respectively) with the fruit fly catch per trap for the first year 2008-09 and (r = 0.243 and 0.280 respectively) for the second year 2009-10. However, in relative humidity negatively correlated for two years (r =-0.218 and-0.182 respectively) recorded with the fly catch. The efficiency of these factors were minimum temperature came first, relative humidity and maximum temperature came second or third in its efficiency. Results of the present investigation may be utilized in chalking out sustainable pest management strategy in the agro-ecological system under consideration.
... The majority originate from and are restricted to the tropical regions [32,33]. However, since establishment of horticultural production in Australia in the 19 th century, several fruit fly species have expanded into more temperate regions, in particular due to invasive expansion and planting of host plants [34]. ...
Background:
Maternally inherited Wolbachia bacteria infect many insect species. They can also be transferred horizontally into uninfected host lineages. A Wolbachia spillover from an infected source population must occur prior to the establishment of heritable infections, but this spillover may be transient. In a previous study of tephritid fruit fly species of tropical Australia we detected a high incidence of identical Wolbachia strains in several species as well as Wolbachia pseudogenes. Here, we have investigated this further by analysing field specimens of 24 species collected along a 3,000 km climate gradient of eastern Australia.
Results:
Wolbachia sequences were detected in individuals of nine of the 24 (37 %) species. Seven (29 %) species displayed four distinct Wolbachia strains based on characterisation of full multi locus sequencing (MLST) profiles; the strains occurred as single and double infections in a small number of individuals (2-17 %). For the two remaining species all individuals had incomplete MLST profiles and Wolbachia pseudogenes that may be indicative of lateral gene transfer into host genomes. The detection of Wolbachia was restricted to northern Australia, including in five species that only occur in the tropics. Within the more widely distributed Bactrocera tryoni and Bactrocera neohumeralis, Wolbachia also only occurred in the north, and was not linked to any particular mitochondrial haplotypes.
Conclusions:
The presence of Wolbachia pseudogenes at high prevalence in two species in absence of complete MLST profiles may represent footprints of historic infections that have been lost. The detection of identical low prevalence strains in a small number of individuals of seven species may question their role as reproductive manipulator and their vertical inheritance. Instead, the findings may be indicative of transient infections that result from spillover events from a yet unknown source. These spillover events appear to be restricted to northern Australia, without proliferation in host lineages further south. Our study highlights that tropical fruit fly communities contain Wolbachia pseudogenes and may be exposed to frequent horizontal Wolbachia transfer. It also emphasises that global estimates of Wolbachia frequencies may need to consider lateral gene transfer and Wolbachia spillover that may be regionally restricted, transient and not inherited.
... There is a long history of ecological and physiological studies of Q-fly and NEO, because Q-fly is Australia's most serious horticultural pest, and a major target for domestic and international quarantine efforts (Drew, 1989;Clarke et al., 2011) In these studies, the two species have shown no differences in pheromones (Bellas and Fletcher, 1979), temperature tolerance (Meats, 2006), or utilisation of a wide range of host fruits -larvae of the two species can even emerge from the same piece of fruit (May, 1953;Gibbs, 1967;Drew, 1989;Hancock et al., 2000). Apart from their mating time difference, the only clearly established ecological difference between the two species is that Q-fly is more invasive than NEO (Drew, 1989;Sved et al., 2003) and has followed the spread of horticulture through eastern Australia (Meats, 1981), including into drier and cooler areas beyond its native habitat (Fig. 1). In historical times Q-fly has regularly appeared in Victoria and South Australia, and there has also been sporadic invasion of Western Australia and Northern Territory (Dominiak and Daniels, 2012). ...
Three Australian tephritid fruit flies (Bactrocera tryoni – Q-fly, Bactrocera neohumeralis – NEO, and Bactrocera jarvisi – JAR) are promising models for genetic studies of pest status and invasiveness. The long history of ecological and physiological studies of the three species has been augmented by the development of a range of genetic and genomic tools, including the capacity for forced multigeneration crosses between the three species followed by selection experiments, a draft genome for Q-fly, and tissue- and stage-specific transcriptomes. The Q-fly and NEO species pair is of particular interest. The distribution of NEO is contained entirely within the wider distribution of Q-fly and the two species are ecologically extremely similar, with no known differences in pheromones, temperature tolerance, or host-fruit utilisation. However there are three clear differences between them: humeral callus colour, complete pre-mating isolation based on mating time-of-day, and invasiveness. NEO is much less invasive, whereas in historical times Q-fly has invaded southeastern Australia and areas of Western Australia and the Northern Territory. In southeastern fruit-growing regions, microsatellites suggest that some of these outbreaks might derive from genetically differentiated populations overwintering in or near the invaded area. Q-fly and NEO show very limited genome differentiation, so comparative genomic analyses and QTL mapping should be able to identify the regions of the genome controlling mating time and invasiveness, to assess the genetic bases for the invasive strains of Q-fly, and to facilitate a variety of improvements to current sterile insect control strategies for that species.
... The two B. neohumeralis stock lines from QDAFF were raised on a similar diet with different concentrations of dried diced carrot (150 g/L), methylparaben (3.33 g/L) and Torula deactivated yeast (50 g/L). Adults from both laboratories were fed sugar and water and a 10:1 protein mix of yeast hydrolysate and sugar [30]. The C. capitata line was raised on larval diet consisting of sucrose (120 g/L), brewer's yeast (80 g/L), wheat bran (240 g/L), methylparaben (2 g/L), sodium benzoate (4 g/L) and 9 mL HCl made up to 1 L with water and adult diet of 3:1 sucrose and yeast hydrolysate mix [31]. ...
Tephritid fruit fly species display a diversity of host plant specialisation on a scale from monophagy to polyphagy. Furthermore, while some species prefer ripening fruit, a few are restricted to damaged or rotting fruit. Such a diversity of host plant use may be reflected in the microbial symbiont diversity of tephritids and their grade of dependency on their microbiomes. Here, we investigated the microbiome of six tephritid species from three genera, including species that are polyphagous pests (Bactrocera tryoni, Bactrocera neohumeralis, Bactrocera jarvisi, Ceratitis capitata) and a monophagous specialist (Bactrocera cacuminata). These were compared with the microbiome of a non-pestiferous but polyphagous tephritid species that is restricted to damaged or rotting fruit (Dirioxa pornia). The bacterial community associated with whole fruit flies was analysed by 16S ribosomal DNA (rDNA) amplicon pyrosequencing to detect potential drivers of taxonomic composition. Overall, the dominant bacterial families were Enterobacteriaceae and Acetobacteraceae (both Proteobacteria), and Streptococcaceae and Enterococcaceae (both Firmicutes). Comparisons across species and genera found different microbial composition in the three tephritid genera, but limited consistent differentiation between Bactrocera species. Within Bactrocera species, differentiation of microbial composition seemed to be influenced by the environment, possibly including their diets; beyond this, tephritid species identity or ecology also had an effect. The microbiome of D. pornia was most distinct from the other five species, which may be due to its ecologically different niche of rotting or damaged fruit, as opposed to ripening fruit favoured by the other species. Our study is the first amplicon pyrosequencing study to compare the microbiomes of tephritid species and thus delivers important information about the turnover of microbial diversity within and between fruit fly species and their potential application in pest management strategies.
... Both species are polyphagous, infesting a very broad range of cultivated fruits and vegetables [1]. However, B. tryoni is considered the more serious pest because, in contrast to B. neohumeralis, it is highly invasive and has followed the spread of horticulture through eastern Australia [2], including into drier and cooler areas beyond its native habitat ( Figure 1a). More recently, Bactrocera jarvisi has been declared a pest in northern Australia [3], although this species has a narrower host range [1]. ...
Among Australian endemic tephritid fruit flies, the sibling species Bactrocera tryoni and Bactrocera neohumeralis have been serious horticultural pests since the introduction of horticulture in the nineteenth century. More recently, Bactrocera jarvisi has also been declared a pest in northern Australia. After several decades of genetic research there is now a range of classical and molecular genetic tools that can be used to develop improved Sterile Insect Technique (SIT) strains for control of these pests. Four-way crossing strategies have the potential to overcome the problem of inbreeding in mass-reared strains of B. tryoni. The ability to produce hybrids between B. tryoni and the other two species in the laboratory has proved useful for the development of genetically marked strains. The identification of Y-chromosome markers in B. jarvisi means that male and female embryos can be distinguished in any strain that carries a B. jarvisi Y chromosome. This has enabled the study of homologues of the sex-determination genes during development of B. jarvisi and B. tryoni, which is necessary for the generation of genetic-sexing strains. Germ-line transformation has been established and a draft genome sequence for B. tryoni released. Transcriptomes from various species, tissues and developmental stages, to aid in identification of manipulation targets for improving SIT, have been assembled and are in the pipeline. Broad analyses of the microbiome have revealed a metagenome that is highly variable within and across species and defined by the environment. More specific analyses detected Wolbachia at low prevalence in the tropics but absent in temperate regions, suggesting a possible role for this endosymbiont in future control strategies.
... Qfly's native range includes coastal regions from north Queensland to northeastern New South Wales (Meats, 1981). Exploiting opportunities presented by European settlement and cultivation of exotic fruiting plants, Qflies expanded their host and territorial ranges. ...
In this paper, informed by more-than-human and biosecurity literatures, I attend a neglected nonhuman considered a serious agricultural pest: the fruit fly. In addressing what it takes to live without fruit flies, biosecurity is theorised as ongoing, enacted achievement sustained (or not) by everyday and eventful interactions of heterogeneous spaces, strategies, and participants—human and nonhuman. Relations of fruits, flies, and people are explored through one vital attempt to biosecure life: Australia’s Fruit Fly Exclusion Zone (FFEZ), a tristate pest-free area established to protect commercial horticulture from the fruit fly. Fruit flies become problematised as their appetites and mobilities confound fruit production and marketing, and affiliated biosecurity controls. Making fruit safe enrolls policy and agricultural sectors, but also more dispersed agents (travellers, residents, trees) and management sites (primarily off-farm). Since its introduction, the FFEZ’s ongoing biosecuring normalised, with only occasional outbreak events. However, recent unprecedented outbreaks evoke questions about the FFEZ’s future status. In such eventful times, it is worth reflecting on what kinds of living are possible in biosecurity zones—for flies, for resident human communities, and for agrifood networks.
... th This expectation largely agreed with the previous recorded studies on some fruit flies. Saeki et al. and [8] Meats mentioned that B. dorsalis (Hendel) and B. [5] tryoni (Frogatt), respectively, have three to eight generations per year. Also Qureshi et al. stated that [7] B. zonata can complete three to nine generations per year in various parts of its range. ...
Some essential biological items of the peach fruit fly, B. zonata (Saund.) Egyptian strain such as time of adult emergence, highest depth of pupation substrate at which the adult could emerge, host preference and number of generations per year; were studied. Results indicated that most of B. zonata adults emerged between 6 a.m and 12 at noon but the maximum emergence took place between 9 a.m and 11 a.m. Ninety percent of adults emerged successfully from pupae situated at 10 cm depth of sand, this percentage decreased gradually with increasing the sand depth till reached to nill at 40 cm depth. The most favouarite host to this fly was pear fruits followed by guava, peach, apple and finally apricot. Present study indicated that B. zonata completed 8 generations per year where the longest generation (56 days) was recorded during winter months and the shortest one (34 days) was recorded during summer months.
... 94 Australia has over 80 endemic species of Bactrocera and Dacus (Drew, 1989), including 95 economically relevant Bactrocera tryoni and Bactrocera neohumeralis, both with an 96 extensive and shared host fruit range from over 40 plant families (Hancock et al., 2000). 97 B. tryoni in particular with its wide climatic adaptation potential and geographic distribution 98 (Meats, 1981;Yonow and Sutherst, 1998) individuals were found in six of these eight species, and seven species shared at least one 106 identical wsp sequence variant. 107 We have now fully characterised the Wolbachia strains from the eight infected tephritid fruit 108 fly species and, for the first time, from two of their parasitoid species, using the MLST 109 approach and a novel allele assignment technique by quantitative allele-specific PCR. ...
Wolbachia are endosymbiotic bacteria that infect 40 to 65% of arthropod species. They are primarily maternally inherited with occasional horizontal transmission for which limited direct ecological evidence exists. Previously, we detected Wolbachia in eight out of 24 Australian tephritid species. Here, we have used Multilocus Sequence Typing (MLST) to further characterise these Wolbachia strains, plus a novel quantitative PCR method for allele assignment in multiple infections. Based on five MLST loci and the Wolbachia surface protein gene (wsp), five Bactrocera and one Dacus species harboured two identical strains as double infections; furthermore, Bactrocera neohumeralis harboured both of these as single or double infections, and sibling species Bactrocera tryoni harboured one. Two Bactrocera species contained Wolbachia pseudogenes, potentially within the fruit fly genomes. A fruit fly parasitoid, Fopius arisanus shared identical alleles with two Wolbachia strains detected in one Bactrocera frauenfeldi individual. We report an unprecedented high incidence of four shared Wolbachia strains in eight host species from two trophic levels. This suggests frequent exposure to Wolbachia in this tropical tephritid community that shares host plant and parasitoid species, and also includes species that hybridise. Such insect communities may act as horizontal transmission platforms that contribute to the ubiquity of the otherwise maternally inherited Wolbachia.
... Although Medfly has occurred within other parts of Australia within the last 100 years, it is widely agreed that it is now only established in Western Australia (Osborne et al. 1997;Waterhouse & Sands 2001;Allwood & Smith 2003;Woods et al. 2005). Many authors report that Qfly is only resident on the east coast of Australia (May 1963;Bateman 1967Bateman , 1972Meats 1981;Elson-Harris 1988;Swaine et al. 1991;Anon 1996;Dominiak et al. 2001;Pike & Meats 2002;Gillespie 2003;Sved et al. 2003;McMaugh 2005;Jessup et al. 2007;Worsley et al. 2008;Shearman et al. 2010). Other authors report that Qfly is only found along the east coast and is not resident in Western Australia or South Australia, although incursions have occurred in these states (Fletcher & Bateman 1983;White & Elson-Harris 1992;Meats et al. 2002;Vera et al. 2002;Bonizzoni et al. 2004;Gilchrist et al. 2004;Campbell et al. 2009). ...
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.
... The prevalence of the invading B. papayae in the towns could be due to the existence of a fruit supply that is more abundant than in natural areas and more continuous than in production orchards, which tend to have fewer varieties (Fletcher 1974). In regions with low rainfall, it can also be due to a more benign microclimate caused by domestic irrigation (Meats 1981;Dominiak et al. 2006) and in tropical areas, to the absence of frugivorous vertebrates (Drew 1987(Drew , 1989. ...
Data from the eradication of the incursion of Bactrocera papayae Drew and Hancock (Dipt.: Tephritidae) in Australia (1995–1998) are used to assess the significance of various aspects of invasion theory, including the influence of towns on establishment, influence of propagule pressure on the pattern of establishment, and the existence of source-sink dynamics. Because there were no sentinel traps in place, considerable spread had occurred before the eradication campaign started. The distribution of fly density around the epicentre in the town of Cairns and a transect along the main traffic routes to the north and south fitted a Cauchy model with a tail having the same slope as a power model with an exponent of −2.4 extending to 160 km. The Cauchy model indicated that 50% of the flies on the transect would have occurred within 3.2 km of the epicentre, 90% within 13.2 km, and 99% within 60 km. The two major satellites at Mareeba (35 km from the epicentre in Cairns) and Mossman (65 km) were not used for the transect data and had respectively 15 and 30 times the density predicted by the model. The proportion of traps that caught flies (a measure of site occupancy) fell with distance from the epicentre. B. papayae was trapped consistently on only three of the 16 rainforest transects that were surveyed and these were relatively close to urban areas where eradication efforts were intense. Despite there being no eradication effort in the rainforest, the trends to extinction were similar to those in adjacent areas. The strategy of initially concentrating eradication efforts on the core and major satellites while maintaining a quarantine barrier at the airport and the boundaries of the infested area appears to be the key to the containment and rapid eradication of the incursion.
... In Australia, the bioclimatic potential of Bactrocera tryoni (Froggart) is related to thermal restrictions. Its altitude limits in the cooler southern parts are set by lethally low minimum winter temperatures (Meats 1981). In related thermotolerance studies with ours, there was no ovarian maturation of some adult tephritids reared at 15°C (Duyck and Quilici 2002;Duyck et al. 2004). ...
The development and survival of immature stages of Bactrocera invadens Drew, Tsuruta and White (Dipt.: Tephritidae), a new invasive fruit fly pest in Africa, was studied in the laboratory at five constant temperatures of 15°C, 20°C, 25°C, 30°C and 35°C and photoperiod of L12:D12. The developmental time of eggs was 5.71 days at 15°C, decreasing to 1.24 days at 35°C. Larval development periods decreased from 35.95 days at 15°C to 6.64 days at 35°C. Pupal development at 15°C took 34.08 days while no adults emerged at 35°C, this being the most lethal temperature. The longest total development period occurred at 15°C (75.74 days) and was shortest at 30°C (17.76 days). The linear model provided a reliable fit of development rates vs. temperature for the immature stages. Lower developmental thresholds that were estimated from linear regression equations for the egg, larva and pupal stages were 8.8, 9.4 and 8.7, respectively. Total degree-day (DD) accumulation was estimated at 376 DD for development from egg to adult emergence. The highest adult survival given as the mean of emergence from a cohort of 50 eggs occurred at 20–30°C. At the egg stage, survivorship was highest at 20–30°C and at the larva and pupa stages, it was at 25°C. The practical implication of the findings is discussed in relation to mass rearing of B. invadens and understanding its biology and ecology.
... 1993), availability of the host plant (Drew et al . 1984), climatic conditions (Messenger & Flitters 1958;Bateman 1968;Meats 1981;Drew & Hooper 1983), phenology of the host plant (Moericke et al . 1975;Prokopy 1977;Katsoyannos 1989), and to a lesser extent may involve parasites and predators (Bateman 1968). ...
Abstract In Queensland, three tomato (Lycopersicon lycopersicum) cultivars, Grosse Lisse, Roma and Cherry, are infested by Queensland fruit fly, Bactrocera tryoni (Froggatt). In this study, we examined if there was a correlation between oviposition preference and offspring performance of B. tryoni among the three tomato cultivars. We also investigated host plant traits that may explain any variation in preference and performance. Choice and no-choice experiments were carried out under laboratory conditions. A positive correlation between oviposition preference and offspring performance of B. tryoni was observed in the three tomato cultivars. Grosse Lisse and Roma cultivars were highly preferred by B. tryoni over Cherry cultivar. Performance (measured as proportion of eggs developing to the pupal stage) was significantly higher in Grosse Lisse and Roma cultivars than in Cherry cultivar. The pericarp toughness of Cherry cultivar appears responsible for its low rate of infestation, while the presence of 2-butanol and 1,4-butanediamine in Roma and Grosse Lisse, respectively, may partly be responsible for the high oviposition preference shown by B. tryoni towards these cultivars.
... The Queensland fruit fly Bactrocera tryoni (Diptera: Tephritidae) is the most destructive pest of horticulture in eastern Australia, due in part to its wide bioclimatic potential (Meats 1981) and its ability to lay eggs in almost all commercially grown fruit (Bateman 1991). The tryoni complex, a grouping of three sibling species native to Australia, also includes the pest B. neohumeralis and the relatively benign B. aquilonis (Drew 1989). ...
— Two sibling species of tephritid fruit fly, Bactrocera tryoni and B. neohumeralis, occur sympatrically throughout the range of B. neohumeralis in Australia. Isolation between the two species appears to be maintained by a difference in mating time: B. tryoni mates at dusk, whereas B. neohumeralis mates during the middle of the day. A morphological difference in humeral callus color also distinguishes the two species. Despite clear phenotypic evidence that B. tryoni and B. neohumeralis are distinct species, genetic differentiation as measured by four markers–nuclear DNA sequences from the white gene and the ribosomal internal transcribed spacer (ITS2), and mitochondrial DNA sequences from the cytochrome b (cytb) and cytochrome oxidase subunit II (COII) genes–is very small. Minor fixed differences occur in the ITS2 sequence, however, in all other cases the two species exhibit a high level of shared polymorphic variation. The close genetic similarity suggests either that speciation has occurred very rapidly and recently in the absence of any mitochondrial DNA sorting or that the sharing of polymorphisms is due to hybridization or introgression. A third species within the tryoni complex, B. aquilonis, is geographically isolated. Bactrocera aquilonis is also genetically very similar, but in this case there is clear differentiation for the mitochondrial loci. The three species form a group of considerable interest for investigation of speciation mechanisms.
Juvenile hormone is an important regulator of sexual development in insects, and application of methoprene, a juvenile hormone analogue, together with access to a protein-rich diet, has been found to accelerate sexual maturation of several tephritid fruit fly species including Queensland fruit fly Bactrocera tryoni (‘Q-fly’). Such accelerated development is a potentially valuable means to increase participation of released males in sterile insect technique programs. However, there is a risk that benefits of accelerated maturation might be countered by increased vulnerability to starvation and desiccation. The present study investigates this possibility. After emergence, flies were treated with three levels of methoprene (0, 0.05%, and 0.5%) incorporated into a diet of sugar and yeast hydrolysate for two days after emergence. Survival of groups and individual flies was assessed under conditions of food stress, food and water stress, and ad libitum access to diet, and survival of individual flies was also assessed under desiccation stress. Most flies provided ad libitum access to diet were still alive at 7 days, whereas all stressed flies died within 4 days. Desiccation stressed flies had the shortest survival followed by food and water stress, and then food stress. Methoprene supplements increased susceptibility of flies to each stress. Flies subjected to food and water stress had the least lipid reserves at death, whereas flies subjected to desiccation stress retained the least water reserves. To investigate mechanisms that might underlie reduced survival under stress; we also quantified activity level of flies that were subjected to food and water stress and desiccation stress. Activity level was greater for flies provided methoprene, but did not vary with stress type or sex, suggesting that increased vulnerability of flies to stress is related to elevated metabolism associated with elevated activity. Deleterious effects of methoprene supplements on stress tolerance indicate a need for careful consideration of the conditions that will be encountered by flies in the field before deploying methoprene as a pre-release treatment in Q-fly sterile insect technique programs.
Following the loss of two key pesticides, dimethoate and fenthion, producers and regulators need to develop new fruit fly management options. A systems approach is a likely measure in the post dimethoate and fenthion era. The risk of fruit fly can be mitigated at the regional, district and farm level. Some measures such as awareness and exclusion are common across all three levels. Pest control measures will be based on an understanding of climate, biology and pesticides. In this present paper, 28 different risk mitigation options that can be used in a systems approach in Australia are discussed.
Close‐range courtship behaviours are a critical element of a species' biology but, if rapid, can often be overlooked. Beyond male chemical and audio calling, close‐range courtship interactions leading to copulation in the Queensland fruit fly Bactrocera tryoni are unknown; this may be due to a true absence or because they have been overlooked and not previously investigated. We sought to resolve the close‐range courtship sequence of B. tryoni and construct an ethogram of identified behaviours. Close‐range video recordings of B. tryoni courtship were taken during the dusk mating window and an ethogram constructed by combining all observed behaviours which led to successful copulation and unsuccessful copulation. While the previously well‐recognised male wing fanning behaviour was documented, a number of other behaviours were identified for the first time in B. tryoni courtship, including female ovipositor extension, and both male and female synchronous supination, face‐to‐face contact, and fore‐ and hind leg interactions. Analyses showed that the total duration of male synchronous supination, but not the number of occurrences, differed significantly between successful and unsuccessful males. Male foreleg interaction with the female abdomen was significantly different in both total duration and total number of occurrences between successful and unsuccessful males. The results reinforce data obtained from other Bactrocera species of simplified courtship sequences in these flies in comparison with other tephritid genera, but nevertheless courtship is more complex than previously recognised.
We analyze the extremely complex problem of fruit fly management in Mexico suggesting the establishment of a long term, well planned and flexible country-wide orchard management program based among others on the following premises: a consideration of the entire fruit fly species complex instead of the common practice of singling out Anastrepha ludens as the unique source of problem; a multistrategy approach in which measures to control fruit flies are integrated with other pest and disease control efforts and all the other agronomic practices used in the orchard; a redirection of the control efforts putting most emphasis in the planting and orchard maintenance phase as opposed to the harvest and marketing phases; the development of novel approaches and the implementation of established control strategies based on ecologically sound principles and that are within the cultural and economic reach of the recipient (more than 70% of the fruit produced in the country comes from small scale, resource poor farmers); a biogeographical division of the fruit growing regions, with the application of management practices adapted to each particular situation; a thorough understanding of the socio-economic, socio-political, cultural and historical milieu of the farmer; the enhancement of alternative means of fruit commercialization through the creation of agroindustries and the enhancement of strong grower associations.
Act 1 – prequel: From the first European settlement to the formation of the Australian Entomological Society, much of Australian entomology was driven by the need to understand and manage a raft of indigenous and invasive pest insect species. This very applied imperative influenced how people approached ecology, which tended to be very much autecological: species focused questions addressing the distribution and abundance of the organism. Not surprisingly that applied focus continued after the formation of the society in 1964, which marks the beginning of Act 2 – The last 50 years. Here I focus in part on what has been published in the flagship journal of the society since its inception and analyse the trends that are evident. The emphasis on basic biology is reflected in the publication trends in the society's journal. I use some of the key native and imported pests – locusts, Helicoverpa, Queensland fruit flies, sugar cane-feeding scarabs, diamondback moth – to illustrate how ecological thinking has developed. There were some Australian giants in the field of population ecology, and their public disagreements continue to reverberate. But there have been many notable contributions by lesser mortals, if only students and their mentors would read and cite appropriately! One can only allude to the encore, or Act 3 – the sequel or the next 25–50 years. The thinking of Australian entomologists continues to be at the forefront of spatial ecology, perhaps reflecting the scale at which fieldwork is undertaken in Australia. Other younger members of the society will no doubt write the epitaph and obituaries of the current crop of researchers and judge their contributions accordingly.
Essential developmental and reproductive attributes of the Oriental fruit fly, Bactrocera dorsalis (Hendel) were studied on five host fruits viz., mango (Mangifera indica), papaya (Carica papaya), guava (Psidium gaujava), sapota (Achras zapota) and banana (Musa acuminate) at 27±1 °C and 65% RH. These studies were carried out to develop economical mass rearing technique for B. dorsalis, which fulfill the supply of good quality fruit flies of specific life stage round the year for various studies. All test host fruits supported the development of B. dorsalis properly from egg to adult emergence. The fecundity of adult flies of F 1 generation emerging from different hosts was at par based on incubation period and fecundity rate. Although all test fruits sustained the full development of B. dorsalis, host fruit played a major role in differential adult emergence, and has positive correlation with fiber content (R 2 =0.87) of the fruit. The cost-effective host fruit for rearing of B. dorsalis is banana followed by guava, sapota, papaya and mango, on the basis of fruit cost and adult emergence per unit weight of fruit.
Detection programs are a specialized aspect of sampling and include quarantine inspections, surveys for rare organisms of conservation value and surveillance trapping for exotic or locally quarantined pests. The aim in each case is to establish whether a given species is there or not with a reasonable degree of certainty. To detect incursions of exotic tephritid fruit fly species into a country, arrays of widely spaced sentinel traps are deployed around points of entry for people and goods, main centres of population and commercial fruit production areas. Response to detection is according to a protocol (code of practice). This includes the installation of a higher density trap array that is used to (a) discover the spatial limits of the infestation, (b) to monitor the effectiveness of the eradication process and (c) to confirm that eradication has in fact occurred when zero flies are caught in the trap array. It takes a very large number of trapping weeks (well over a year) to achieve confidence limits on zero of useful size. However, a much shorter period of zero trapping is needed to calculate a useful probability for some density (or index of density) that we know to be non-viable or would find acceptable for other reasons. This chapter deals with such problems in terms of rationally argued risk levels using examples of management of Medfly in South Australia and California. Because risk arguments involve the length of time when trapping arrays catch no flies (fly-free periods), attention is also given to the techniques of temperature and development summation and how daily temperature records, calendar time and generation time are related. Finally, the impacts of any improvements in trap efficiency, trap placement and data management are considered, especially with respect to telemetry, delimitation and extinction modeling.
Abstract: Causal mechanisms in population dynamics in the absence of feedback to density are examined using Thrips imaginis, Tipula paludosa and Dacus tryoni as examples.
Because many plants regulate their internal temperatures, there is no a priori reason to believe air temperature accurately reflects the temperatures faced by tephritid larvae inhabiting fruit interiors. Larvae also move across and burrow into soil to pupate, and immature flies at this point are also likely to encounter temperatures that might be less than or exceed air temperature. Using thermocouples and a computerized data logger we measured a range of temperatures in the 4 major hosts of Anastrepha suspensa (Loew), the Caribbean fruit fly: (Surinam cherry Eugenia uniflora L., Cattley guava, Psidium cattleianum Sabine, guava, Psidium guajava L., and loquat, Eriobotrya japonica (Thunb.)), and in grapefruit, Citrus paradisi Macf, an economically important secondary host. Generally, temperatures were higher in the southwestern portions of tree canopies relative to those in the northeastern interiors. Fruit on the ground was warmer than in the tree, but there was no significant pattern of maximum fruit core temperatures being warmer than subcutaneous pulp. Soil temperatures were also higher than fruit-in-tree temperatures, and decreased and displayed less variance with increasing depth. Fruit in trees seldom reached temperatures +/- 0.05 of air temperatures, but fruit on the ground could be more than 0.25 the adjacent air temperature. There were positive relationships between the ratio of mean and minimum fruit temperature/adjacent air temperature and fruit diameter. Information on the temperatures confronted by immature fruit flies can be used to model population dynamics, and to design temperature sensitive strains through conditional gene expression for mass-rearing and release.
The abundance of the Queensland fruit fly, Dacus tryoni (Froggatt), is greatest in the tropical-sub- tropical part of its range in Queensland and declines towards its southern extreme in Victoria, where conditions are not very favourable for survival in winter or for a rapid rate of increase in summer. The rate of detection of larval infestations and the level of trap catches of adults indicate that Melbourne (southern Victoria) has had a very low population of D. tryoni each summer for at least 8 years and probably for the last 30 years. Field cage studies in Melbourne, of cohorts started each month as eggs, pupae and teneral adults, indicated that adults emerging from mid-April to mid-May could survive to breed in the following spring. It appears that adults emerging earlier would not survive to produce eggs in spring, and that adults would not be expected to emerge later in autumn because the survival rates of larvae are very low and the survival rate of pupae is zero in winter months. Times taken f
We examine procedures for declaring an area free of pest fruit flies following an eradication campaign. To date, the acceptable period of trapping zero flies has been calculated without an estimate of the probability of being wrong. The zero trapping periods are usually shorter when declaring local 'area freedom' from an endemic fly, than when claiming eradication of an exotic species. We use a model to calculate the probability of zero trap captures and therefore the probability of trapping further flies. The latter probability is always finite. A zero trapping result does not indicate the absence of flies. There must also be evidence of what constitutes a non-viable density, as indicated by the trapping rate. The non-viable densities of certain pest fruit fly species are known from decades of managing small incursions in fly-free zones. There is no need for implementation of eradication procedures if the trapping rate is sufficiently low, in these areas. For a given density of flies (defined in terms of expected mean catch per trap per week), the probability of zero trap captures reduces with time and the number of traps employed. If the model calculations use a non-sustainable density (inferred from trapping rate) then we may declare the actual density of flies to be less if the trapping result is zero for a given number of weeks with a given number of traps when the model predicts the probability of such a result to be sufficiently low, according to a criterion that is selected at a level suited to the purpose of the declaration.
We report the first widespread survey of tephritid fruit flies attempted in a single time period. 1,471 cue lure traps caught 17 species, and extensions to previously recorded geographical ranges were detected for seven of them: Bactrocera tryoni, B. neohumeralis, B. frauenfeldi, B. aeroginosa, Dacus absonifascies, D. aequalis and D. newmani. the traps also unexpectedly caught several B. cacuminata and also both males and females of Dirioxa pornia and Ceratitis capitata. the geographical variation in the relative abundance of B. tryoni and B. neohumeralis in the region of their co-occurrence was in substantial agreement with earlier estimates. the regional variation in abundance of B. tryoni in the eastern states was in accordance with the predictions of a published bioclimatic model. Furthermore, the spread of this species (expected from the model) to several locations in the Northern Territory is recorded here for the first time.
Abstract The Queensland fruit fly (Q-fly), Bactrocera tryoni, is a serious horticultural pest throughout eastern Australia, and apart from isolated outbreaks, is absent from Adelaide and South Australia. Considerable resources are put into preventing the entry of Q-fly into South Australia and the eradication of any outbreaks. Nevertheless, some flies are still trapped in Adelaide and, because known permanent populations are too distant for unaided dispersal, these flies must arrive as larvae in infested fruit. To provide authorities with more information on the nature of and the extent of outbreaks, the authors used 26 microsatellite markers to test the relationships between outbreak flies caught in Adelaide in 2000 and 2002. Groupings between individuals were tested using both a model-based clustering method (implemented in the Structure program) and relatedness testing, using both simple exclusion tests and relatedness coefficients. While many flies appeared unrelated, one group of at least six full sibs was detected, all of which were trapped in the same month. Unexpectedly, these six flies were trapped at sites separated by distances greater than the unaided dispersal distance of Q-fly, implicating human-aided dispersal of infested fruit within Adelaide. Thus simultaneous trappings of flies separated by kilometres are not necessarily separate outbreaks as has been assumed. The implications for current outbreak control strategies are discussed.
CLIMEX, a climate-matching model, is described in relation to pest risk assessment. The rationale for the development Of CLIMEX is given and its various functions are illustrated with examples, using the Colorado beetle Leptinotarsa decemlineata. The beetle's climatic requirements are first inferred from its native distribution in North America. They are then used to project the relative favourableness of Europe and Asia for population growth and persistence. The role is illustrated Of CLIMEX, in association with PESKY, a prototype version of a generic expert system for pest risk assessment, in the assessment of the risk of the beetle being transferred from France to China. Finally, CLIMEX is used to search for places in North America with climates best matching that of Beijing (CN), in order to target collection of possible biocontrol agents for use against the beetle in that area, should it become established there.
Microclimate and host plant architecture significantly influence the abundance and behavior of insects. However, most research in this field has focused at the invertebrate assemblage level, with few studies at the single-species level. Using wild Solanum mauritianum plants, we evaluated the influence of plant structure (number of leaves and branches and height of plant) and microclimate (temperature, relative humidity, and light intensity) on the abundance and behavior of a single insect species, the monophagous tephritid fly Bactrocera cacuminata (Hering). Abundance and oviposition behavior were signficantly influenced by the host structure (density of foliage) and associated microclimate. Resting behavior of both sexes was influenced positively by foliage density, while temperature positively influenced the numbers of resting females. The number of ovipositing females was positively influenced by temperature and negatively by relative humidity. Feeding behavior was rare on the host plant, as was mating. The relatively low explanatory power of the measured variables suggests that, in addition to host plant architecture and associated microclimate, other cues (e.g., olfactory or visual) could affect visitation and use of the larval host plant by adult fruit flies. For 12 plants observed at dusk (the time of fly mating), mating pairs were observed on only one tree. Principal component analyses of the plant and microclimate factors associated with these plants revealed that the plant on which mating was observed had specific characteristics (intermediate light intensity, greater height, and greater quantity of fruit) that may have influenced its selection as a mating site.
Weekly fruit fly captures for a 12-month period on Mt Glorious (south-east Queensland) suggested that at higher altitudes very few flies survived the winter and that there was an annual colonisation of the higher altitudes by flies from the lower altitudes. The peak trap captures of Dacus tryoni (Froggatt) and Dacus neohumeralis Hardy corresponded with the fruiting times of their major hosts. The fly populations increased with the onset of higher temperatures and the beginning of the summer rain period and decreased with the decline in temperature and rainfall in autumn. Studies on Dacus cacuminatus (Hering) showed that when environmental conditions are suitable this species efficiently exploits its host resulting in rapid population increases.
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