Farmnote 101/1994 [Reviewed May 2006]
By Ian Dadour, Entomologist, South Perth
The stable fly irritates cattle, horses, pigs, dogs, cats and humans by its painful bite and loss of blood. Cultural and chemical control measures are described.
Stable fly or dog fly (Stomoxys calcitrans) is often a pest of livestock around animal enclosures, stables and feedlots. Stable flies are also important pests in range or pasture situations. Stable fly is generally present in large numbers from mid-spring to mid-autumn, but localised outbreaks can occur in many regions of south-western Australia when winters are mild.
Figure 1. Adult stable fly
Effects on livestock
Stable fly is a blood-sucking parasite and is one of the most important pests of cattle and horses. It is also a pest of dogs, cats, pigs, humans and many other short haired mammals. Injury is caused by irritation from its painful bite and loss of blood.
Cattle and horses tend to dislodge stable fly by foot stamping, tail switching and throwing their head down toward their front legs. In cattle and horses it generally leads to reduced weight gains and damage to tissue and hide.
When flies are abundant cattle and horses will bunch, with each animal trying to get to the centre of the group, or try to stand in water to avoid harassment. This continual movement causes cattle and horse to go off their feed. The bunching behaviour adds to the danger when the weather is hot. Weight gain depressions of 250 g/day in beef cattle and milk production decreases of 30 to 40 per cent in dairy cattle have been recorded.
Recent research has shown that 50 to 100 stable fly per animal can cause significant reduction in weight gains in feedlot situations. In the United States, five stable fly per front leg is the point where animal behaviour changes (bunching) and economic losses begin. The economic threshold is 25 flies per animal.
Stable fly have also been implicated in the transmission of several pathogenic organisms, but are not considered a major vector of any cattle disease in Australia.
The complete life cycle of the fly, from egg to adult, is about 13 to 18 days in temperatures ranging from 24 to 30C. The female lays her eggs on fermenting organic matter or animal manure in association with other organic matter. The eggs are white and similar to housefly eggs and are laid in groups of 25 to 50 after a blood meal. Adult females, which live about 25 days, lay an average of 800 eggs, generally in material containing much vegetative matter.
Eggs hatch in 1 to 2 days and the larvae are white maggots. The larvae develop for 6 to 8 days, and the pupal stage (chestnut brown) lasts 6 to 8 days. In warmer areas the stable fly may breed all year and in lower temperatures (10C) development from egg to adult takes 3 to 5 months.
Areas of breeding are common in silage, bedding mixed with urine and faeces, rotting hay, straw or sawdust, fermenting feed, piles of grass clippings, along the edges of feeding aprons, under fences and along stacks of hay or straw and in effluent drainage areas.
The adult stable fly is about the same size as the house fly, but differs in having a broader abdomen and a checkerboard of dark spots on the back of the abdomen (Figure 1). The main distinguishing feature is its mouthparts (Figure 2). The stable fly has a stout black proboscis that is used to pierce the skin and imbibe blood.
Figure 2. House fly head (left) and stable fly head (right) showing differences in the mouthparts (proboscis)
Stable fly stay on the animal long enough to obtain a blood meal (2 to 5 minutes for engorgement), then seek a shaded place on a fence, wall or vegetation to digest it. They feed at least twice each day. Males also feed on blood but less frequently. Females need 6 to 8 days of feeding before breeding starts.
Cultural practices for control
Sanitation must be the first step in a control program. Remove manure, or spread it in thin layers for drying before incorporating it into a heap. Regularly (weekly) clean around silage pits and feed aprons, under fences and gates, around water systems and at the edge of dung mounds. The stable fly breeds in older manure mixed with dirt, feed and moisture.
Manure should only be stockpiled in a fly proof enclosure. A cheaper alternative would be to cover the stockpile with plastic and completely seal it around the base. Both methods require a concrete base to stop any run-off from rain on to surrounding soil or vegetation.
The Williams Trap consists of two white Alsynite panels at right angles to each other, 1 m above the ground and painted with Tac-gel (sticky substance) - see Figure 3. Place the trap in direct sunlight. Heat the Tac-gel in a water bath (bain-marie) until it becomes a viscous liquid and then apply it with a brush.
Figure 3. Williams Trap - sticky translucent panels for trapping stable fly
This trap can be modified to a single white sheet of anything disposable (painters drop sheet or white card) and placed on a wire fence or clothes line (Figure 4). It is best to mount materials like plastic and soft fabrics in a frame. Once the trap is covered in flies, dispose of it in the rubbish bin. Set as many traps as necessary.
Figure 4. Modified Williams Trap - sticky white sheet hung from a clothes hoist
The Table lists several insecticides that are registered for the control of flies. Those listed under Larvae in manure can be used on litter under poultry; those under Stockpiled manure are only for use on heaps of manure not in contact with stock.
The flies rest on shady surfaces (fences, walls of silage pits, buildings and vegetation) after temperatures reach 27C. Apply residual sprays to these surfaces, since resting flies absorb the insecticide, which kills them. Residual insecticides are effective for about 7 to 10 days, but rain, high temperatures and ultraviolet light all reduce the residual effect.
Fly control products Product Active Ingredient Residual Â- Adult flies Baygon 800 800g/L Propoxur Ficam W 800g/L Bendiocarb Dyfly Plus 10g/kg Methomyl Coopex R.I. 25g/kg Permethrin Cislin 10 10g/L Deltamethrin Responsar 50g/L Cyfluthrin Demon 400g/kg Cypermethrin Knockdown Â- Adult flies Reslin 50g/L Bioresmethrin 400g/L Piperonyl Butoxide Larvae in manure Dipterex 500SL 500g/L Trichlorfon Dipterex SP 800 800g/L Trichlorfon Stockpiled manure Vapona 500g/L Dichlorovos Neocid 200P 200g/L Diazinon
Apply residual sprays to the point of run-off, but do not allow puddles to form, and do not contaminate food or water.
There are several insecticides that can be used to control stable fly around farm buildings and feedlots, but none are very effective against stable fly populations in pasture or range situations. Stable fly feed primarily on the legs of stock where it is difficult to administer insecticides with enough residual activity to kill the fly.
Area sprays are short residual, knockdown insecticides. Use these sprays as low-concentrate, fine mists. They are most efficient when flies are concentrated at resting sites (early morning, late afternoon or during the hottest part of the day). Sprays lose effectiveness at temperatures below 21C.
Residual sprays are the most effective method of control, but area sprays (foggers) can be the most efficient if application is at optimum times. A combination of the two methods is the best fly management strategy:
- area sprays knock down the existing fly populations, and
- a residual spray applied a week later against newly emerged flies.
Alternate these methods throughout the fly season.
Insecticides applied directly to animals for fly control are ineffective, because many applications are required, which can stress livestock.
Design of animal enclosures
Fly breeding occurs where moisture, manure and soil are mixed. Good drainage is essential around any livestock buildings. The accumulation of water in association with manure increases the potential of stable fly to breed.
- Farmnote No. 57/91 'Fly control on dairy farms' (Agdex 410/614).