Buffalo fly control in cattle

Incidence of buffalo fly

In Queensland, buffalo fly has 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 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 season is usually shorter with flies disappearing from most areas during winter.

Effect on cattle

Buffalo flies irritate cattle, interrupt feeding and cause sores, especially when infestations are high. Trials in the wet tropics have shown that buffalo fly can reduce beef cattle production by up to 16%.

A small parasitic worm (Stephanofilaria spp.) is associated with buffalo fly bites and causes skin lesions. Sores from buffalo fly infestations result in permanent hide damage, decreasing the value of the hide. These lesions may also restrict access to the live export trade.

Dark-coated cattle, bulls, older cattle and those in poor condition usually attract the heaviest infestations of fly. Bos indicus cattle seem to carry high numbers but do not appear to be as severely affected as other breeds.

Chemical resistance

Chemical resistance is usually seen in the field as a reduced protection period. Trials undertaken in 1993 showed resistance to synthetic pyrethroids (SPs) was widespread. There was also cross-resistance (i.e. if flies were resistant to one SP chemical they were also resistant to other SP chemicals).

At these trials, there was little evidence of resistance to organophosphate (OP) chemicals. However, anecdotal evidence since then has suggested that OP resistance may have developed, with reduced protection periods being experienced.

Control strategies

The current buffalo fly control strategies aim to:

• reduce buffalo fly numbers to acceptable levels to prevent production loss
• provide for welfare considerations
• minimise chemical residue risks
• reduce reliance on chemicals by using alternative control methods
• target treatment costs and consider alternative treatments for different herd groups.

Available options

Non-chemical control wherever possible

Tolerating some fly burden and controlling fly without chemicals by using methods such as the Buffalo Fly Tunnel Trap and dung beetles will help to minimise resistance problems and reduce possible residue risks.

Where chemical control is necessary

Monitor fly numbers. Also, delay treatment of beef cattle until fly worry is obvious on the focus animals (those most susceptible to flies, such as bulls) or when animals are carrying in excess of 200 flies per animal (100 per side). High-producing dairy cattle may require treatment at lower levels of infestation.

Self-treatment methods

Use the effective OP chemicals in backrubbers or insecticidal ear tags during the peak buffalo fly season.

Another option is the Buffalo Fly Tunnel Trap.

OP sprays

OP chemicals can be used for opportunistic spray treatments when cattle are in yards for other husbandry purposes. They may also be required if there are excessive fly numbers on cattle prior to commencing or following self-treatment control methods.

Coordinating with neighbours

Use the same chemicals and treat at the same time as your neighbours.

Chemical control methods

Chemical use should aim to limit the spread and control the development of resistance. It is critical to apply products correctly to delay development of resistance. If products are used according to manufacturer’s label directions, the amount and concentration applied should be sufficient to control susceptible populations of buffalo fly.

If mixing rates and/or application method are not carried out according to the directions, this will lead to sub-lethal levels of active ingredient being applied - a recipe for selecting for resistance.

Combining incorrect mixing and/or application with increased frequency of application causes the selection pressure for resistance to rise further. There is also an increased risk of chemical residues in meat products.

The following tables show options for chemical (Table 1) and non-chemical (Table 2) control methods.