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Buffalo Fly

Overview

Buffalo fly are consistently rated as one of the most economically important animal health issues affecting the profitability of beef and dairy operations in Queensland.

Cause

The buffalo fly, Haematobia irritans exigua, is a small biting fly 3.5 – 4 mm long. It feeds off cattle and buffalo, and causes irritation which can result in reduced production, if cattle are heavily infested.

Incidence

Buffalo fly are found throughout northern Australia, in north-west Western Australia, the Northern Territory, Queensland and the north-east of New South Wales. In coastal areas of Queensland and far northern NSW, infestations can be present year round. Buffalo fly are less of a problem in southern inland areas of Queensland and into inland NSW because there are shorter periods of warm wet weather and the winters are colder. Fly numbers in these areas are generally lower during winter with the peak later, often during late summer/autumn.

Impact

Buffalo flies live permanently on their host, the females only leaving to lay eggs in freshly deposited dung pats. They feed 10–40 times each day and can only live for 1 or 2 days off the host. The life cycle from egg to egg takes less than 14 days under optimal conditions of hot humid weather, but is extended during cool weather.

Newly emerged flies seeking their first host can fly up to 8 km in the search. Movement of infested animals can be an important method of longer distance spread between herds.

Buffalo fly infestations vary from animal to animal. Bulls and dark-coated cattle, especially black cattle, seem to carry the largest fly burdens. Apart from obvious animal welfare impacts, lower weight gain and lower milk production have been measured in heavily infested cattle.

Some cattle are ‘allergic’ to buffalo flies and are intensely irritated by as few as 4 or 5 flies. These cattle scratch and rub themselves constantly, which results in large sores on their necks and sides. The value of the hide is reduced when cattle have developed skin sores as a result of buffalo fly infestation.

Some sores present on cattle, especially in the corner of their eyes or on their necks are caused by a parasitic nematode Stephanofilaria stilesi which is transmitted by buffalo flies between cattle.

Management and Control

It is generally considered that infestations of more than 200 flies per animal (100 per side) for beef cattle or 30 per dairy cow (15 per side) are necessary to reduce production. Fly infestations can vary significantly between animals, even in the same mob.

An integrated approach to buffalo fly control is needed to:

  • Cost effectively reduce the buffalo fly population to levels that are not affecting production
  • Ensure the welfare of animals
  • Prolong the effective lifespan of chemicals used by alternating chemical groups and integrating non-chemical mechanisms
  • Minimise chemical residue risks.

Non-chemical control options

Culling allergic cattle

This is a long term strategy for prevention of the impact of Buffalo fly in a breeding herd. Care must be taken not to confuse the lesions caused by Stephanofilaria with allergy, as culling the former will have no impact on breeding a herd with buffalo fly resistance.

Buffalo fly traps

Buffalo fly traps can reduce fly populations by up to 70% but have practical limitations. They are limited to situations where cattle can be trained to use them on a regular basis such as in dairies or cell-grazing situations.

Dung beetles

Dung beetles reduce buffalo fly populations by removing or spreading dung so that the flies cannot breed in it. They are most active in hot, humid weather, which coincides with the period of high fly activity.

Chemical control options:

Ear tags

Insecticide-impregnated plastic ear tags are the most widely used method of buffalo fly control in Australia. The tags slowly release chemicals over a defined period. Cattle grooming and interaction deposits chemical from the tags onto the shoulder, back and flanks of treated animals. Tags must be removed at the end of the payout period to avoid exposing flies to sub-lethal doses of chemical.

Sprays and Dips

Sprays are applied as backline or full body sprays/dips. Multiple treatments are generally required throughout the season. Sprays must be mixed and applied correctly in order to obtain effective chemical levels on the cattle. Failure to follow label directions may result in poor results and hasten development of resistance. Cattle should be treated in a race and not in a yard.

Pour-ons

A number of pour-on products have registered claims for buffalo fly control. They must also be applied correctly but their relative ease of use makes them attractive to some producers for buffalo fly control.

Back rubbers/side rubbers/rubbing posts

These devices allow self-application of chemicals when cattle rub against them. This also provides relief from fly irritation. Back rubbers are economical and suitable for points where cattle congregate such as watering points or supplementary feeding points.

Chemical residues

It is imperative that correct dosages and methods of application are followed with all products used for buffalo fly control. Producers must also ensure that the Withholding Period and Export Slaughter Interval are observed for any products used.

Chemical resistance

Buffalo fly, like other parasites, can become resistant to insecticides. Integrating non-chemical means of control into a control program will aid in slowing resistance development.

Chemical resistance to most of the registered buffalo fly control chemicals is now confirmed or suspected. The more frequently a chemical is used the more rapidly resistance will develop. The use of sub-lethal doses of chemicals has also been implicated as a cause of resistance. This can occur if label recommended dose rates are not applied or if ear tags are left in past their recommended payout period.

It is generally recommended that producers alternate their use of chemicals in fly tags and use Organophosphate tags for 2 years and then a Synthetic Pyrethroid tag for 1 year.

Summary

Buffalo fly are an economically important parasite of cattle, mostly present in north and north-eastern parts of Australia. They cause significant production impacts if left uncontrolled. A range of control options exist, but an integrated approach using both chemical and non-chemical control options will give the bes

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