Fly Management in Udder Health Programmes

By Dr Vincent Turner on 05 December 2023

The causes of udder health problems in dairy cows are multifactorial in nature. In South Africa, especially because of favourable climatic conditions, flies can have significant adverse effects on udder health in dairy herds. Fly problems can be prevented if an Integrated Fly Management Programme (IFMP) is adopted.

Houseflies (Musca domestica) and biting flies (Stomoxys calcitrans) breed in manure, decaying vegetation and other moist accumulations of organic matter found in the dairy cows’ environment. Ideal fly-breeding areas and conditions often occur in zero-grazing systems, calf-rearing areas and where the indiscriminate disposal of effluent from the parlours is practiced.

It is essential to implement an IFMP early in the fly season and before the adult fly population has reached virtually uncontrollable levels.

Fly-Breeding Management

At any one time 80 to 85% of the fly population is in the non-adult stage of the breeding cycle (eggs, larvae and pupae within the breeding material). It therefore stands to reason that the successful prevention of fly problems must be spearheaded at breaking the breeding cycle.

Good Dairy Farming Practices amongst other things dictate cleanliness, good drainage and the constant removal of manure and other organic matter (eg. bedding) from around the parlour and calf-rearing areas. Effluent from the parlour must be collected in adequately designed and managed slurry dams. All potential fly-breeding areas must be eliminated as a part of an on-going fly management activity.

Complementary to these practices specific procedures directed at the fly larvae and pupae should be included in the IFMP. Eco-friendly chemicals can be scattered in potential fly-breeding areas where on ingesting the chemical the larvae are prevented from pupating.

The biological control of flies is highly effective if implemented correctly. This involves the scattering of eco-friendly fly parasite pupae (wasps) in the fly-breeding areas. The hatched wasps locate the fly pupae, feed off the fly larval tissue inside the pupae thereby breaking the fly breeding cycle. This, in turn, starts a wasp breeding cycle in the fly-breeding area where the wasps continue to actively parasitise the fly pupae. For several reasons the introduced wasp colonies gradually diminish in number and additional wasps must be re-introduced to the fly-breeding areas on a scheduled basis.

Adult Fly Management

Visible adult flies represent only about 15% of the local fly population. However, adult flies are the breeders and their numbers must be reduced at all times. The effective control of adult flies involves the strategic use of fly traps, baits and surface sprays.

Pheromone traps should be positioned no higher than one metre off the ground around the perimeter of animal holding areas such as calf-pens, cow camps and the parlour’s loafing yards. The traps must be correctly managed and maintained.

Chemicals used as baits and sprays for adult fly knock-down should be rotated using different active molecules every 9 to 12 months to minimize the development of resistance by the flies.

Granular baits should be sprinkled lightly in strategic areas such as calf-rearing facilities.

Residual surface sprays should be applied monthly on walls, roof eaves and trees where flies roost in the early morning or in the shade in the heat of the day.

An IFMP demands that a scientific approach be adopted and strictly implemented to prevent fly breeding and control adult flies. This should be an essential component of the good dairy management practices necessary to protect and promote the udder health of all dairy animals.

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