Fruit flies

Taxonomy, biology and managementTaxonomy, biology and management(and some key references and names)(and some key references and names)

Paul FerrarPaul Ferrar

Fruit fly taxonomy

Order Diptera (flies)

Family TephritidaeSubfamily 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– 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)

• 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:• 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

• BaggingFruit 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:– 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!