Annals of Applied Biology ISSN 0003-4746
REV I EW ART IC LE
The ecology of Bactrocera tryoni (Diptera: Tephritidae):
what do we know to assist pest management?
A.R. Clarke1,2, K.S. Powell3, C.W. Weldon4 & P.W. Taylor5
1 Discipline of Biogeoscience, Faculty of Science and Technology, Queensland University of Technology, Brisbane, QLD, Australia
2 Cooperative Research Centre for National Plant Biosecurity, Bruce, ACT, Australia
3 Biosciences Research Division, Department of Primary Industries, Rutherglen, VIC, Australia
4 Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
5 Department of Brain, Behaviour & Evolution, Macquarie University, Sydney, NSW, Australia
Keywords
Applied ecology; area-wide management;
Dacinae; tropical fruit fly.
Correspondence
A.R. Clarke, Discipline of Biogeosciences,
Faculty of Science and Technology,
Queensland University of Technology,
GPO Box 2434, Brisbane, QLD 4001, Australia.
Email: A.clarke@qut.edu.au
Received: 28 January 2010; revised version
accepted: 19 September 2010.
doi:10.1111/j.1744-7348.2010.00448.x
Abstract
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.
Introduction
Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) is one
of Australia’s worst horticultural pest insects, attacking
most fruit and many vegetable crops (Drew et al.,
1978; Bateman, 1991; Hancock et al., 2000). Its native
distribution is considered to be tropical and subtropical
coastal Queensland and northern New South Wales
(Gilchrist et al., 2006), but it is now more widely
established in eastern Australia and has invaded some
South Pacific island nations (Drew et al., 1978). Outbreaks
have also occurred and then been eradicated in other
Australian states where the fly does not normally occur
(e.g. South Australia (Maelzer, 1990a,b) and Western
Australia (Ayling, 1989)). Adult flies lay their eggs into
fruit and the larvae, which feed within the fruit, cause
direct fruit damage and induce decay and premature fruit
drop. Economic losses, estimated at $28.5 million/annum
in 2000 (Sutherst et al., 2000), result from direct yield
losses, direct and indirect management costs and loss or
limit to domestic and international markets. Expenditure
on fruit fly activities in Australia (with the vast majority
focused on B. tryoni) was estimated at $128 million in the
years 2003–2008 (PHA, 2008). This expenditure included
direct control costs, postharvest treatments, on-going
surveillance for area freedom and research.
The literature on B. tryoni began over 115 years ago
(Tryon, 1889) and now includes over 450 refereed papers
and book chapters, at least 40 research masters and PhD
theses, and a large ‘grey’ literature. The entire literature
26 Ann Appl Biol 158 (2011) 26–54© 2010 The Authors
Annals of Applied Biology© 2010 Association of Applied Biologists

A.R. Clarke et al. Ecology of B. tryoni
has never been reviewed, although components have
been included in generic fruit fly reviews (Bateman, 1972;
Fletcher, 1987), specialist book chapters (e.g. Fletcher,
1989a,b; Meats 1989a,b; Drew & Romig, 2000) and as
part of modelling exercises (Yonow & Sutherst, 1998;
Yonow et al., 2004). With a literature this large it might
be assumed that we know all we need to know about
this pest, but as we will make clear in this review, while
we have very detailed information about select aspects of
the insect’s biology, much knowledge of the organism’s
general biology and ecology, particularly that pertinent
to developing sustainable pest management options, is
largely lacking.
As a major pest species, B. tryoni has been the focus of
several major research initiatives over the last 50 years
(work before the 1950s was sparse, although the works of
Allman (1938, 1939, 1941; Allman & Friend, 1948) and
Jarvis (1922a, b, c, 1923, 1924,1925a, b, c, 1926a, b, 1931)
are notable exceptions). However, paradoxically, most
research (at least the published research) has not focused
on issues related to the control of the fly. Rather, major
blocks of work have focused on very specific theoretical,
physiological or ecological issues, including: the density
dependence/independence debate; speciation and the
timing of mating behaviour as an isolating mechanism;
rapid physiological adaptation following movement of the
organism into a previously unfavourable environment;
bacteria as a fruit fly food source; and male pheromones.
While there are some obvious exceptions, including the
literature covering postharvest disinfestation treatments
and a body of more recent work derived from activities
associated with the southern fruit fly free zone and
the sterile insect technique (SIT), most of the available
B. tryoni literature cannot be used to directly support pest
management research.
While stating that the majority of research work on
B. tryoni is not generally applicable to pest management,
we are not implying that every paper on the fly should
address a specific management issue or practice. Rather,
we believe that targeted behavioural, physiological and
ecological research is needed to progress Queensland fruit
fly control, a view which has been well argued for pest
systems in general (Walter, 2003).
Why is targeted behavioural, physiological and eco-
logical research pertinent to B. tryoni management and
why is it important now? Management of B. tryoni is cur-
rently undergoing a crisis. Two chemicals, dimethoate and
fenthion, long used for in-field control and postharvest
commodity treatment, are expected to have substantially
restricted use following current reviews by the Aus-
tralian Pesticides and Veterinary Medicines Authority
(PHA, 2008). In their absence, in-field management of
the fly will need to rely on alternative control strategies.
For B. tryoni, these will include controls which manipulate
the fly’s use of resources. Such resources include protein
food sources (manipulated through protein-bait sprays),
male parapheromones (manipulated through male anni-
hilation technique), mates (manipulated through SIT),
noncommercial host plants and noncrop habitats (manip-
ulated through habitat management). The better appli-
cation of biological controls, largely ignored for the last
50 years, may also become important. To make these
alternatives viable replacements for chemical treatments,
or to maintain their use (e.g. in the case of area freedom),
a new period of intensive research on B. tryoni is begin-
ning (as illustrated by the recent release of the National
Fruit Fly Strategy (PHA, 2008)). Our current review,
summarising what we know and what we do not know
about B. tryoni behaviour and ecology with reference to
pest management, is part of this larger process.
This review focuses initially on the species status of
B. tryoni and closely related taxa within the B. tryoni
complex. It then presents a summary of the distribution
of Queensland fruit fly, factors limiting that distribution
and likely changes in distribution under climate change.
The remainder of the review focuses on major control
techniques, identifying what we know and do not
know about the fly based on the information required
for the techniques to be successfully implemented or
improved. In this way we hope not only to cover existing
information, but also to identify and justify priority
issues for further research. This review does not touch
on postharvest controls or regulatory controls (e.g. road
blocks, Interstate Certification Assurances, community
awareness programmes) and also excludes, because of
space constraints, the very large literature pertinent to
the SIT which is dealt with in a companion paper.
Bactrocera tryoni complex
Accurate species identification is a central tenet of
successful pest management (Paterson, 1991; Walter,
2003). While this may appear a simple and self-
evident statement, defining species is not always a
straightforward task. Tephritid fruit flies, along with
other groups (e.g. mosquitoes, Rona et al., 2009; Weitzel
et al., 2009), often contain groups of biologically distinct,
but morphologically similar or indistinguishable species
(=sibling species, or species complexes). Sibling species
can vary in important biological traits such as host
use, pest status, geographic distribution and seasonal
phenology (Barik, 2009; Clarke et al., 2001; Garros et al.,
2006). Within the economic fruit flies, the best-known
species complexes include the Anastrepha fraterculus
complex (Ca´eres et al., 2009), the Ceratitis rosa complex
(Virgilio et al., 2008), the Bactrocera dorsalis complex
Ann Appl Biol 158 (2011) 26–54© 2010 The Authors 27
Annals of Applied Biology© 2010 Association of Applied Biologists