More than just a nuisance, flies directly affect cow comfort, reduce production and spread disease.
Effective fly control is never about a single product or tactic. Instead, it requires a whole-farm approach that integrates hygiene, monitoring and carefully timed interventions.
Dairy cattle are particularly vulnerable to fly pressure, and the most problematic species are buffalo flies, stable flies and houseflies.
Stable flies reduce milk yield by irritating cattle, leading to bunching, stomping, tail flicking and reduced feeding time.
Buffalo flies and houseflies are important vectors of disease and can spread pinkeye (infectious bovine keratoconjunctivitis) and mastitis pathogens.
Beyond animal health, flies create stress for farm workers, reduce the quality of the working environment, and damage the farm’s public image when numbers become obvious.
The cornerstone of any fly-control program is sanitation, because flies require moist, decaying organic matter to reproduce. Manure, wet feed, silage spills, and damp bedding are the most common breeding sites.
Breaking the cycle means regular scraping and removal of manure from lanes, feedpads and, where applicable, barns and sheds. Once removed, manure should be spread or composted quickly to reduce its suitability as a breeding site.
Spilled feed should not be left to accumulate, and silage faces need to be kept tight and well covered.
Managing drainage around troughs and laneways is also important, because even small patches of standing water mixed with organic matter can support large numbers of flies.
Monitoring is another vital part of fly control.
Sticky traps, baited traps, or simple counts of flies on cattle legs or backs give a useful indication of pressure. More than 10 stable flies per cow leg or obvious behavioural changes linked with fly worry should trigger action.
Regular monitoring also helps assess whether control measures are working and provides an opportunity to rotate strategies before resistance builds.
Timing matters, too. Beginning treatments early in the season, such as October, ensures cows are protected before peak fly pressure develops. Waiting until flies are abundant usually means that large populations of eggs, larvae and pupae are already established, making control much more difficult.
A wide range of tools is available, and the best choice depends on the farm system.
Biological control using parasitic wasps and beetles can reduce fly larvae in manure. These work best when combined with good hygiene, as they cannot manage heavy infestations alone.
Chemical options such as insecticide sprays, pour-ons, ear tags and dust bags are widely used to reduce adult fly numbers, but rotation of chemical classes is essential to avoid resistance.
Physical and environmental strategies are also valuable. Flies dislike air movement, so fans in dairies and sheds not only assist with cow cooling but also reduce fly worry.
Walk-through traps, fly barrels, sticky boards and bait stations can all help to lower fly numbers when used consistently.
No single approach is perfect, and the best results come from combining methods in a thoughtful and strategic way.
Fly control should be considered part of the wider herd health plan rather than a standalone task.
Reducing fly pressure lowers stress, improves feed intake and cuts down on the spread of infectious diseases. This translates directly into better production, fewer treatments and improved animal welfare.
Talking with your veterinarian about fly control during herd health reviews ensures strategies are tailored to your farm, taking into account herd size, grazing patterns and regional fly pressure.
Flies are a yearly challenge for dairy farms, but with a proactive and integrated approach they can be kept under control.
Hygiene, monitoring and a balanced combination of biological, chemical and physical management tools are the foundation.
Farms that stay ahead of the fly season not only protect cow comfort and health but also reap the benefits of higher productivity and a better working environment.
Dr Rob Bonanno is regional lead veterinarian for ProDairy and is based in Gippsland.
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