Transcript Slide 1

Fruit flies
Taxonomy, biology and management
(and some key references and names)
Paul Ferrar
Fruit fly taxonomy
Order Diptera (flies)
Family Tephritidae
Subfamily Dacinae
Genus Bactrocera
• Contains most of the important pest species of Asia
and the South Pacific
• Genus Dacus also important in Africa
Important Bactrocera species
• Bactrocera dorsalis – Oriental fruit fly
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A complex of closely related species:
Bactrocera dorsalis (many hosts)
Bactrocera papayae (many hosts)
Bactrocera carambolae (many hosts)
• and others (at least 75 different species so far)
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Bactrocera cucurbitae – melon fly (in cucurbits)
Bactrocera tau – also in cucurbits
Bactrocera latifrons – solanum fruit fly
Bactrocera minax – citrus fruit fly
Important Bactrocera species
• Bactrocera occipitalis – mango, guava, citrus
• Bactrocera philippinensis – mango, papaya,
jackfruit
• Bactrocera umbrosa – jackfruit, breadfruit
• Bactrocera zonata – hosts in Family Rosaceae,
including peach, but also other families
Oriental fruit fly complex
• For general management purposes,
probably OK to regard all members of
complex as Bactrocera dorsalis
• But where export crops are concerned,
exact species must be known – quarantine
authorities will insist on it
Fruit fly life cycle
• Eggs – female lays into fruit with a sharp, pointed
ovipositor – may also inject fruit-rotting bacteria
• Larvae – three larval instars – feed in fruit
• When fully fed, 3rd instar larva drops to the ground,
crawls away (usually into soil) and develops into a
pupa (inside hard shell of 3rd instar larval skin, called
a puparium)
Attractants and trapping
• Male lures – main ones are:
– Methyl eugenol (ME)
– Cuelure
• Female lures (not developed yet)
• Protein baits – hydrolysed protein
including yeast
– Lynfield traps
– Steiner traps
Lynfield trap
Steiner trap
Fruit fly damage
• Larval tunnelling and feeding damages
fruit
• Bacteria also enter and rot the fruit faster
• Crop losses can be from a few per cent
to 100%
Management of fruit flies
• Cover spraying
– Advantage:
• Effective
– Disadvantages:
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Very expensive in pesticide
Very time-consuming in labour
Kills beneficial organisms/harms environment
Harms health of farmer doing the spraying
Can leave chemical residues in fruit
Management of fruit flies
• Bagging
Fruit is covered with a layer of some material
– Advantages:
• Effective when applied properly
• Often increases fruit quality (and price)
• Materials usually cheap
– Disadvantage:
• Very laborious to apply
Bagging of fruit
Cultural controls
• Grow less susceptible varieties
• Harvest fruit early (before fruit fly attack
occurs
• Crop hygiene and sanitation – clear away
old, fallen, infested fruits
Protein bait spraying
• Dilute protein bait is mixed with pesticide
– Was malathion, now chlorpyrifos, fipronil or
Spinosad
• Small squirt or splash is applied to leaves
of trees scattered through orchard
– Not necessary to treat every tree – flies are
attracted over a considerable distance
Protein bait spraying
• Advantages:
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Cheap in materials
Much safer for health of operator
Less pesticide into environment
No impact on non-target organisms
No risk of residues when applied correctly
• Disadvantages:
– Still needs labour, though much less than bagging or
cover-spraying
– May need to be repeated during fruit cycle
Protein bait spraying
• To show farmers how well it works:
– Put a white sheet on the ground under leaves
that have been sprayed with protein
bait/insecticide
– Many dead flies will accumulate!
Other techniques for control
• Male annihilation
– Many blocks impregnated with male attractant
and pesticide are distributed widely
– Males feed on these and die
– Females remain unfertilised and cannot breed
• Not suited to individual farmer use
Other techniques for control
• Sterile insect technique
– Huge numbers of sterile males are released in an
area
– Females mate with them and remain unfertilised –
cannot breed
– Million dollar operation
• Not suited to individual farmer use
Case study in northern Vietnam
• Peaches were promoted as an alternative
to opium
• Grow well in climate of northern Vietnam,
but 100% of crop was destroyed by
Bactrocera pyrifoliae
• Bait spraying was introduced, and losses
now reduced to < 5%
– Young children have now seen their first ever
ripe peaches!
Contacts and references
• Paper distributed contains various
references to key works on fruit flies that
may be of help
• Also key institutions and scientists that
may be able to help
– Dr S. Vijaysegaran – wide expertise in Indian
subcontinent, Southeast Asia and Australia
Methods for identifying fruit flies
• Morphological versus molecular
– See Appendix of paper for some notes on this
• Review paper on Bactrocera dorsalis
complex:
eprints.qut.edu.au/3257/1/3257_1.pdf
PERCEPTIONS
• Don’t forget:
• You may only think
about fruit flies
• The farmer has to
think about ALL the
problems on the
crop!
THANK YOU!