Testing flies for resistance to flystrike preventative and treatment chemicals

If you are concerned your population of flies is showing resistance to the chemicals you use, you can have a resistance test carried out.

NSW DPI are now conducting laboratory tests, which are open to producers from all states, to determine the presence of resistance to various chemicals.

You will need to supply a large sample of live, healthy Lucilia cuprina maggots to the laboratory.

Collection instructions

1. Contact the laboratory to get a collection kit, with detailed instructions sent out to you.

Narelle Sales, NSW DPI 
Elizabeth Macarthur Agricultural Institute
Direct T: 02 4640 6446 Switchboard T: 02 4640 6333

E: narelle.sales@dpi.nsw.gov.au

2. When a flystruck sheep is found, take it to the shearing shed and ideally machine shear, rather than hand shear the strike wound to recover more maggots—at least 60 healthy maggots are required.

  • Place the sheep on a large piece of plastic or similar (about 2 metres x 2 metres; a woolpack will be okay, but harder to handle), then shear the wound and a surrounding 5 cm clear area.
  • After shearing, move the sheep away to a nearby pen for later treatment.
  • Shake the shorn wool to dislodge the maggots onto the plastic and clear away the remaining wool (no wool should be sent).
  • At least 60 healthy Lucilia cuprina maggots are required.
  • The information supplied in the kit includes a photo of the type of maggot that should not be included as they eat the Lucilia maggots in transit.
  • Being careful not to crush the maggots, remove any obviously damaged maggots and then lift the plastic into a funnel shape and slide the remaining maggots into the collection kit and screw on the lid.**

3. Keep the container of maggots out of the sun in a cool place, but NOT the refrigerator or freezer.

4. Complete and include the required submission form.

5. Post the sample to the laboratory the next day if possible, use the Reply Paid Post Pack supplied, and include the completed submission form.

** If the proper collection kit is not immediately on hand, you can use a fully sealable container (e.g. two plastic vitamin containers) with about 6 needle holes in each lid (no bigger or the maggots escape) and a small handful of completely dry dirt or sand that does not contain any small pebbles.

The insecticides that can be tested, with examples of the products containing them, are as follows:

  • Dicyclanil and cyromazine e.g. Clik and Vetrazin
  • Ivermectin e.g. Coopers Blowfly and Lice
  • Spinosad e.g. Extinosad
  • Imidacloprid e.g. Avenge + Fly

Each of the dot points above represents a different insecticide group.


  • $346.18 for all 4 insecticide groups (as above)
  • $336.18 for 3 groups
  • $326.18 for 2 groups
  • $316.18 for 1 group

Further information

Narelle Sales, NSW DPI 
Elizabeth Macarthur Agricultural Institute
Direct T: 02 4640 6446 Switchboard T: 02 4640 6333

E: narelle.sales@dpi.nsw.gov.au


Identifying and managing resistance

Resistance of flies to preventative and treatment chemicals can be managed to slow the development, especially if caught early—before obvious signs of resistance.

>> More information about resistance

>> More information about signs of possible resistance and what to do about it (see the pdfs on this page).