SHEEP LICESHEEP LICEECONOMIC LOSSECONOMIC LOSS -- $123million PA$123million PA
Lost production:Lost production:
* lousy sheep cut about 10% less wool* lousy sheep cut about 10% less wool
(up to $12/head for fine wool!)(up to $12/head for fine wool!)
* cotted wool is worth about 10% less* cotted wool is worth about 10% less
•• decreased tensile strengthdecreased tensile strength
•• yellow d scolouration of wool yellow discolouration of wool
•• Cockle Cockle devalues hidesdevalues hides
•• increased susceptibility to flystrikeincreased susceptibility to flystrike
2mm
BovicolaBovicola ovisovis
SHEEP LICESHEEP LICE• Opportunities to eliminate lice from individual sheep are ‘off-shears’ (0-24h after shearing) ORin ‘short wool’ (1-42 days after shearing).
• Treatments applied at other times may reduce lice numbers to the extent that fleece damage is arrested but will not eliminate theinfestation.
SHEEP LICESHEEP LICE REGISTERED INSECTICIDES:REGISTERED INSECTICIDES:
•• PyrethroidsPyrethroids ((cypermethrincypermethrin, , deltamethrindeltamethrin, , alphamethrinalphamethrin) ) (pour(pour--onsonsand sprayand spray--on)on)
•• Organophosphates (Organophosphates (temephostemephos(dip),(dip), diazinondiazinon (spray(spray--on, dip on, dip under APVMA permit))under APVMA permit))
•• BenzoylphenylBenzoylphenylurea (urea (IGRsIGRs) () (triflumurontriflumuron (pour(pour--on),on),
diflubenzurondiflubenzuron) ) (dip pour(dip and pour--on)on)
•• IvermectinIvermectin (jetting (jetting fluid)
•• Magnesium fluorosilicate/sulphur Magnesium fluorosilicate/sulphur (dip) (dip) –– approved for organicsapproved for organics
•• SpinosadSpinosad(dip and pour(dip and pour--on) on) –– approved for organicsapproved for organics
•• ImidaclopridImidacloprid (pour(pour--on) (soon)on) (soon)
SHEEP LICE SHEEP LICE WHEN THINGS DON’T GO AS PLANNED
CONTROL FAILURE – occurs when a pesticide application does not control a pest as well as expected.
• This may reflect the unrealistic expectations of the producer, failure to apply the product correctly (dose/head and as per label directions), failure to provide adequate prevention from re-infestation post-treatment, or insecticide resistance.
SHEEP LICE SHEEP LICE –– pyrethroidpyrethroid resistanceresistance
•• Laboratory diagnosisLaboratory diagnosis
10 fold difference - enough for pour-ons to fail
SHEEP LICE SHEEP LICE –– pyrethroidpyrethroid resistanceresistance
1986 1986 --Low level resistanceLow level resistance•• pourpour--onsons failedfailed
1992 1992 -- HartleyHartley strainstrain• 640+ fold resistance!• pour-ons and dips failed!
Extreme resistance then became increasingly common and widespread
640 fold difference
SHEEP LICE SHEEP LICE –– managingmanagingpyrethroidpyrethroid resistanceresistance
••Resistance to one Resistance to one pyrethroidpyrethroidconferred resistance to them allconferred resistance to them all
•• No crossNo cross--resistance resistance to organophosphatesto organophosphates
HARTLEY
SHEEP LICE SHEEP LICE –– organophosphate resistanceorganophosphate resistance
•• only one only one dia inondiazinon--r si tant resistant popu ation (population (‘‘ rangeOrange’’ found) found
• for resistance managementnote the susceptibility of the note the susceptibility of the ‘‘ OrangeOrange’’ strain to strain to pyrethroidspyrethroidsand the susceptibility of the and the susceptibility of the ‘‘ HartleyHartley ’’ strain to strain to diazinondiazinon
SHEEP LICE SHEEP LICE –– IGR resistanceIGR resistanceAIM: To develop a laboratory test capable of measuring the susceptibility of lice populations to diflubenzuron with a view to diagnosing resistance if it exists.
Normal cuticle Chitin deficient cuticle – note the thin band of normal cuticle
SHEEP LICE SHEEP LICE –– IGR resistanceIGR resistanceHYPOTHESIS: That if they exist, ‘IGR-resistant’ female lice would be capable of laying eggs that would hatch, following treatment with doses of diflubenzuron that prevent hatching of eggs laid by ‘susceptible’ females.
Experiment: 40-50 female lice were treated with 0.2 µL of diflubenzuronsolution, provided with wool and adequate food and kept under ideal conditions in the company of males. Egg laying and hatching was monitored over 19 days.
SHEEP LICE SHEEP LICE –– IGR resistanceIGR resistance
0660.05
0520.025
12570.0125
14590.0063
26580.0031
40600.00156
3658Control
Number of nymphs hatched by Day 19
Number of adult lice still alive at Day 19
Diflubenzuron dose(µg per louse)
IGR-susceptible’ – Claremont strain (low-range pyrethroid resistance/IGR naive)
SHEEP LICE SHEEP LICE –– IGR resistanceIGR resistance
IGR-susceptible’ - Hartley strain (highly pyrethroid resistant/IGR naive)
0180.10
0200.05
0150.025
6350.0125
4240.0063
9330.0031
8300.00156
1944Control (acetone)
Number of nymphs hatched by Day 24
Number of adult lice still alive at Day 24
Diflubenzurondose
(µg per louse)
SHEEP LICE SHEEP LICE –– IGR resistanceIGR resistance
IGR Field Failure: Stanthorpe (Qld) strain
22490.20
17430.10
17190.05
18400.025
8150.0125
1330.0063
26370.0031
11180.00156
1425Control (acetone)
Number of nymphs hatched
by Day 19
Number of adult lice still alive at
Day 19
Diflubenzurondose
(µg per louse)
SHEEP LICE SHEEP LICE –– IGR resistanceIGR resistance
RESISTANCE IS REAL!RESISTANCE IS REAL!• complaints common
• no distinctive regional distribution (NSW/Qld/WA/Vic)
• tell-tale signs are immature lice on treated sheep
• history of repeated use of IGRs for lice and/or blowflies
• labels now refer to ‘susceptible’ strains
• will become more common if IGRs continued to be used