Insect worry in livestock

Following floods or major rain events, the populations of biting insects usually increase significantly. These insects include buffalo fly, midges and mosquitoes, and may also include stable fly and other biting flies.

Animals are adversely affected by such insects in two ways:

• persistent biting causing distress (a welfare consideration) and the associated loss of production due to distress, excessive walking and failure to feed out properly
• transmission of diseases by insects (three-day sickness being the most common).

Several problems that arise in addressing the problem of insect worry include that:

• animals usually cannot be mustered for some time after floods or rain because it is not possible to get onto country or cattle will not work on boggy country, even if using ATVs or helicopters. This limits the options for treatment significantly
• there are limited chemicals registered for use on insects other than buffalo fly
• retreatment with the same or related chemicals at short intervals is prohibited due to the high risk of development of tissue residues and the possibility of toxicity issues.

Note: when using chemicals, always refer to the directions on the container. These directions give the species that can be treated, dose rates to use, retreatment intervals and withholding periods to observe before sale for slaughter.

How to treat insect worry

If stock can be mustered and handled through a race

• Pour-on preparations should work. A number of deltamethrin preparations are available with registrations for use that include buffalo fly, stable fly and for Culicoidies brevitarsus (one of the biting midges).
• Application of insecticidal ear tags should give relief from susceptible insects such as buffalo fly.
• If only buffalo fly control is needed, other pour-on preparations are available.

If stock can be mustered or confined in a small yard

• You can overspray cattle with suitable chemicals such as Fenvalerate or Chlorfenvinphos for buffalo fly. Note that there may be resistance problems with some chemicals, so you should seek advice from knowledgeable local suppliers on suitable chemicals. You can also use Fenvalerate on horses to prevent or treat Queensland itch caused by Culicoidies brevitarsus.

If stock can't be mustered but are frequently using watering points or cattle camps, or working specific areas

• You could erect back rubbers in places that cattle frequent. Chlorfenvinphos is registered for use in back rubbers.
• You could light and maintain smoky fires. Insects are repelled by smoke. It may be necessary to ensure stock feed out at least some time.