Stable fly in Western Australia

Page last updated: Wednesday, 4 October 2017 - 12:57pm

Please note: This content may be out of date and is currently under review.

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.

On 2 September 2013 stable fly was included as a declared pest under the Biosecurity and Management Act 2007, administered by the Department of Agriculture and Food, Western Australia (DAFWA). New regulations are in force to manage this pest in 11 designated local government areas.

Stable fly has been an annoying pest for many years along the coastal plain north and south of Perth where it is present in large numbers from late spring through to late autumn.

Its management falls under the Biosecurity and Management Act 2007  which is administered by DAFWA. This Act specifies management to reduce fly breeding in 11 designated local government areas, being the cities of Armadale, Cockburn, Kwinana, Rockingham, Swan and Wanneroo, and the shires of Chittering, Gingin, Harvey, Capel and Murray (coastal plain portion only) and Serpentine–Jarrahdale.

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