Stable fly in Western Australia

Page last updated: Wednesday, 1 September 2021 - 11:52am

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Stable fly (Stomoxys calcitrans) is an international insect that has become an aggravating pest in Western Australia, particularly on the coastal plain, north and south of Perth. It can attack humans, domestic pets and livestock, seeking to draw blood which is essential to complete its life cycle. Stable flies typically occur in large numbers from late spring through to late autumn.

On 2 September 2013, stable fly was included as a declared pest under the Biosecurity and Agriculture Management Act 2007 (BAM Act) for the following 14 designated local government areas:

  • City of Armadale
  • City of Cockburn
  • City of Joondalup
  • City of Kwinana
  • City of Rockingham
  • City of Swan
  • City of Wanneroo
  • Shire of Capel
  • Shire of Chittering
  • Shire of Gingin
  • Shire of Harvey
  • City of Kalamunda
  • Shire of Serpentine–Jarrahdale
  • and the portion of the Shire of Murray described as the Peel-Harvey Coastal Plain Catchment State Planning Policy No. 2.1

Where stable fly is a declared pest, Local Government Authority (LGA) officers can apply to be authorised under the BAM Act to undertake compliance activities. Please contact your LGA to enquire if compliance activities are being undertaken in your area if stable flies are a problem for you. You can also make a report on the MyPestGuide™ Reporter app.

The Biosecurity and Agriculture Management (Stable Fly) Management Plan 2019 was published in the Western Australian Government Gazette No. 127 (3 September 2019). This updated plan replaces the Stable Fly Management Plan 2016, and outlines the measures to be taken to control stable fly in areas where it is a declared pest.

The Stable Fly Management Plan 2019 includes the control measures from the previous plan as approved measures for a period of two years. This will allow for the transitioning from the old plan to the updated plan measures. Please note, this transition phase ends on 03 September 2021. After this date the control measures from the previous plan will no longer be approved measures.

Periodically the Stable Fly Management Plan 2019 may be modified to allow new measures and/or control methods to be adopted. To maintain the integrity of the Stable Fly Management Plan 2019, only new measures and/or control methods that can be proven to result in similar control rates will be adopted.

LGA officers who wish to become authorised under BAM Act to undertake compliance activities for stable fly should email: stablefly@dpird.wa.gov.au to request information on becoming authorised under the BAM Act for stable fly.

Impact on livestock

Stable fly is closely associated with human activity and can be a serious pest of livestock around animal enclosures, stables, feedlots and paddocks or pastures.

It is sometimes known as biting fly and is a problem for cattle, horses, goats, dogs and humans because of its painful bite as it draws blood during feeding.

For detailed information on prevention and mitigation of stable fly for livestock owners please refer to the Livestock Producer Manual located on the right-hand side of the web page.

Cattle and horses are most affected. Animals will try to avoid the fly by stamping their feet (Figure 1), tail switching, throwing their heads down toward their front legs, and kicking sand up onto their legs and body.

Horses are seen to stamp when stable flies bite their legs.

Stable flies on horse legs
Figure 1 Horses stamp when stable flies bite their legs

This can lead to reduced weight gain from continual movement and allergic reactions on their skin from the flies' feeding. When stable flies are present in large numbers (more than 20-30 per animal), cattle will often bunch together in an effort to get to the centre of the group and avoid the fly, or they may stand in open water to avoid being bitten.

This continual agitation reduces the animal’s normal grazing time and they may move to feeding at night when the fly is not active. Bunching together by cattle is particularly hazardous in summer where animals can be at risk of heat stroke.

Cattle form bunches when stable flies begin biting them
Figure 2 Cattle bunch together when stable flies begin to bite them

Stable fly numbers can be monitored by counting the flies on all four legs of about 10 animals. When the average number is more than 25 flies per animal (treatment threshold), action is needed. At more than 25 flies per animal, measurable reductions in weight gain and condition occur and numbers above 50 flies per animal can reduce weight gain by 25% and milk production by 40–60%.

For detailed information on prevention and mitigation of stable fly for livestock owners please refer to the Livestock Producer Manual located on the right-hand side of the web page.

Contact information

Pest and Disease Information Service (PaDIS)
+61 (0)8 9368 3080

See Also