Incidence of Buffalo Flies
Cattle producers throughout Northern Australia regard the buffalo fly (Haematobia irritans exigua) as a serious pest. In all recent cattle industry surveys, producers have nominated the buffalo fly as the major parasite problem of cattle. Increased resistance to the synthetic pyrethroid (SP) range of chemicals by the buffalo fly population has meant a reduction in the effectiveness of some chemicals. Combined with this, the prevalence of buffalo flies has increased further south over recent years.
In Queensland, buffalo flies have a similar geographical distribution to that of the cattle tick occurring along the coast and across the north. The heaviest populations occur in the wet tropics. Mild winters and wet summers permit a southern and western spread into normally buffalo fly-free areas. In northern Queensland, the main fly season extends from November to April with lower numbers present for the rest of the year. In southern Queensland, the main buffalo fly season is usually shorter with flies disappearing from most areas during winter, although some may survive through winter in protected coastal areas. 1
Buffalo flies are small (3.5 mm to 4 mm long) blood-sucking parasite of cattle in warm moist areas but they also cause intense annoyance to horses running with or near cattle. Each fly feeds up to 20 times a day by puncturing the skin and taking blood. Their territory extends southward across Australia, and these biting flies are adept at building up resistance to insecticides.
Signs of Buffalo Fly Infestations
In horses, skin irritation and open sores encrusted with small dark flies with long flat wings. Buffalo flies may completely cover the backline of cattle and rise up in a cloud if disturbed. They do not otherwise leave the animal except to lay eggs in freshly deposited dung.
Control of buffalo flies in cattle has typically included an ever-changing variety of sprays, pour-ons, walk-through dusts, insecticide-impregnated ear tags and insect growth regulators in feed 2.
Buffalo flies are a serious problem for the Queensland dairy industry. In heifers, the main loss in production is due to reduced growth as fly irritation reduces feed intake. Reduction in growth in dairy heifers can lead to milk production reduction and reproduction performance.
Other costs of buffalo flies include:
Hide damage is common because buffalo flies cause irritation, which leads to self-inflicted wounds. Hide damaged downgrades leather value in the processing industry and represents a loss to the industry. Buffalo flies also transmit stephanofilaria worms, which are responsible for the characteristic raised-edge, raw lesions on the cattle. A heavy infestation of buffalo flies may result in hair loss on irritated areas around the eyes of cattle and an increase in the incidence of blight.
Management of external parasites is necessary for proper biting fly management and to prevent effects on animal performance and avoid animal welfare issues. Best practice aims at achieving this through correct management with minimal pesticide usage to avoid residues in milk or meat and risk of development of chemical resistance in parasites.
Controlling buffalo flies on heifers involves the same treatment program as the milking herd. Treatment should occur at the same time as the milking herd to achieve maximum control on the farm. Coordinating treatment with neighbours is also advisable. Chemical and non-chemical control options are available.
Avoid chemical use for buffalo fly management, where possible. Biting fly control without chemicals such as biting fly traps, encouraging dung beetles and tolerating some fly burdens will help to minimise resistance problems and reduce possible residue risks. Dark-coated heifers and those in poor condition usually attract the heaviest infestations of buffalo flies. One strategy is to consider culling highly sensitive cattle.
Buffalo fly traps can have significant success in reducing buffalo fly populations. Dung beetles can also reduce the buffalo fly breeding success by burying and spreading the cattle dung.
An effective buffalo fly control program requires a strategy that gives optimal control with the least number of treatments to reduce the:
Monitoring of biting fly numbers is useful when chemical control is necessary. Delay treatment until biting flies become obvious on the cattle that are most susceptible to the biting flies, or when you can observe cattle carrying more than 200 flies per animal (100 per side).
The costs of handling cattle, particularly heifers, that are not regularly yarded are often underestimated. To reduce the time and money spent on cattle treatment and handling, consider self-treatment methods. These include the various 'back rubbers' and dusting appliances.
Another option is to use ear tags during the peak buffalo fly season. Consider alternating tags of different chemical groups each year or second year. Alternating the chemical groups may slow the onset of resistance of buffalo flies to the chemicals. Use sprays or pour-ons before the peak season so that the effective life of the eartag covers the worst of the buffalo fly season.
Care for Dung Beetles
Some chemicals used to treat buffalo flies kill dung beetles. Particularly, avoid these chemical treatments of buffalo flies in the spring when the dung beetles are first emerging. Dung beetle populations are most vulnerable to losses from chemical use at these times.
Coordinate Parasite Treatments
Coordinate buffalo fly treatments with other parasite control treatments to reduce the number of chemical treatments applied specifically for buffalo flies. Research in America showed that a treatment for internal parasites with a macrocyclic lactone in late autumn hindered the development of resistance in the buffalo flies to the routine treatments.
All treatments require adequate facilities and equipment that will allow the safe and effective treatment of heifers. These facilities and equipment require maintenance to keep them in good working condition.
Avoid chemical residue problems by reading the product label carefully and strictly adhering to withholding periods.
Correct application of chemicals is essential in controlling the development of insect resistance. Failure to observe the directions in regard to application rates or methods will lead to the application of sub-lethal levels of active ingredient, which may select for resistance in buffalo flies. Avoid overdosing heifers with chemicals.
Always read the label carefully and use the products only as directed and follow all safety instructions for the handling of chemicals and the disposal of unwanted chemicals and containers. 3
Buffalo fly infestations are recognised as one of the most important causes of animal health problems for beef cattle in Queensland. Each fly feeds up to 20 times a day by puncturing the skin and sucking blood from its victim.
The discomfort suffered by cattle infested with buffalo flies is obvious to producers and all those who observe cattle at the time. The welfare of the cattle is important when considering treatment of the flies, and realisation of economic loss estimates helps to rationalise management decisions.
Losses caused by buffalo fly infestation are mainly due to reduced feed intake of the cattle. Individual cattle will vary in their response to buffalo fly infestations, mainly due to individual variations in threshold levels in their immune systems.
Most cattle can tolerate a small number of buffalo flies without a detectable loss in production. Australian research has shown that buffalo fly numbers of less than 100 per animal can have an effect on weight gain in cattle. Research in the related horn fly in North America showed a reduced growth rate with as few as 12 flies per animal. In dairy cattle, a threshold of 30 flies resulted in adverse effects on milk production.
There are many different effects of buffalo fly infestations on cattle. Unfortunately determining a production loss solely attributable to the effects of buffalo flies has often been difficult. The following summaries give indications of expected effects on cattle due to buffalo flies.
1. Reduction in Weight Gain
In Queensland beef cattle, a moderate infestation of as few as 200 buffalo flies can cause a range of losses in production, including weight losses averaging 15 kg over a 100-day fly season.
Similar research in America on the related horn fly also recorded a range of losses in the weight gains in cattle. For a moderate infestation of horn flies over a 100-day fly season, the reduction in weight gains of the cattle averaged 8 kg.
2. Reduction in Weight Gain of Calves
Buffalo flies can also cause a reduction in weight gain of calves due to reduced milk production in lactating cows. This has been measured in dairy cows and a moderate infestation of 200 flies reduced milk production by more than half a litre each day per cow.
Buffalo fly infestation can lead to the development of lesions in cattle. These lesions add to the discomfort of cattle and reduce the hide values. One Queensland study showed that about 40% of steers and bullocks not treated for buffalo flies had buffalo fly related lesions compared to no lesions in a comparative group that had been treated for buffalo flies. This was repeated in the following year and about 60% of the untreated cattle had lesions compared to less than 2% of the cattle treated to control buffalo flies.
Generally, there is no relationship between the number of flies on an animal and the presence or absence of lesions in cattle not treated for buffalo flies. This suggests that lesions may be due to individual sensitivity rather than related to the number of flies.
Most of the buffalo fly related lesions were around the eye or in the mid-neck region.
One Queensland trial showed that nearly 30% of cattle not treated for buffalo fly control suffered from pinkeye during one season compared to no development of pinkeye in cattle that were treated for buffalo fly. 4
Buffalo flies live permanently on their host, the females only leaving to lay eggs in freshly deposited dung pats. Each biting fly feeds many times each day (range 10 to 40) and can only live for 1 or 2 days away from the host animal.
Adult buffalo flies live for 2 to 3 weeks, and females lay eggs from 4 days after they commence sucking blood, and continue to lay eggs until they die.
The eggs of Buffalo flies hatch in 15 to 24 hours under favourable conditions, and hatching rates are greatest between 25°C and 35°C.
Buffalo fly larvae burrow into dung, moving further into the pat as the surface layers dry out. Optimal larvae survival occurs at about 25°C and 75% to 85% dung moisture content – under these conditions, the buffalo fly larvae growth is usually completed in 4 to 5 days.
Pupation of buffalo flies takes place in or under the dung pad, and adults emerge in 3–5 days under these conditions. Freezing of the dung pad, such as occurs in a heavy frost, kills any larvae or pupae present in the dung.
The life cycle from egg to adult fly (Figure 1) takes 9–11 days. The life cycle from egg to egg takes 12–14 days, but this time period may extend to several weeks if the weather is cool. 5
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Get rid of biting march flies and stable flies with Epps Biting Fly Trap™ – Portable as your herd moves from paddock to paddock.