Fly control in cattle: the options compared

As many dairy and beef systems have intensified, so too has the need for effective fly control programmes that combine cleanliness with chemical, biological or physical controls – or all three, depending on the farm situation.

Flies start breeding from the end of March, so vet Tom Jackson recommends getting started on controls right now.

“I don’t think any farm can get to a point where there are no flies, and no need for chemical, biological or physical controls, but it is certainly possible to reduce populations and the volume of chemicals needed.”

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“Start as early as possible in the season: if you can get control of flies before they begin breeding, it will be more effective than waiting for them to establish their populations,” says Mr Jackson, of Shropshire-based LLM Farm Vets.

“It is a long way back once the breeding population has got out of control. Although you are never going to reduce fly populations to zero, if you can keep them under control you will be in a much better situation as the season progresses.”

Options for controlling flies

Chemical pour-ons

Several pour-on products applied to the backs of animals are available, based on synthetic pyrethroids such as permethrin and deltamethrin.

In an average summer, three or four treatments are usually required.

Ear tags containing cypermethrin are also available.

Effectiveness

Very effective – most will kill flies on contact.

Pros	Cons
Ease of use Most have zero milk withdrawal requirements and can be used during pregnancy and lactation Effective against all the major fly pests	Provide little protection to the udder area Potential issues with resistance Use of synthetic compounds may come under pressure in future

Cost

The cost is weight-related to avoid overdosing. The cost for a 650kg cow can range from 58p to £1, depending on the product.

Tags are available at £2.70 and give season-long coverage, although in heavy infestations two tags might be necessary.

Chemical sprays

An insecticide is applied as a water emulsion via a knapsack sprayer or spray arch.

Effectiveness

Very effective but there is risk of insecticide washing off during heavy rain.

Pros	Cons
Insecticide can be applied to specific parts of the animals, such as the udder area, during periods when animals are at high risk from disease	Good handling facilities are essential Applications are weather-dependent High labour requirement – fortnightly applications are usually needed Difficult to apply spray evenly

Cost 

£35 will cover 50 litres of spray, which works out at less than 10p per treatment for each cow.

Biological

Fly parasites are introduced on to farms by trained veterinary technicians to inhibit the breeding population of nuisance flies.

The parasites actively search for nuisance fly eggs.

Female parasites pierce the nuisance fly pupae to lay their eggs. The parasite larvae hatch and eat the contents of the nuisance fly pupae before progressing to parasitise more nuisance fly larvae themselves.

This helps to control the nuisance and biting fly populations at source.

Effectiveness

This method is effective in intensive housed systems, calf sheds and parlours.

Parasitic flies can be killed in cold weather, so the programme should be carried out annually. Over time there should be a reduction in overall fly population, leading to reduced quantity of parasites required.

Pros	Cons
A sustainable approach to fly control Fly population is naturally reduced over time Used as part of a wider fly control strategy, it reduces use of synthetic products	Fly parasites should be distributed every two weeks to help build up a population of fly parasites Not as effective in extensive grazing systems where cows are at grass for longer periods

Cost

Friendly Flies supplied by LLM Vets are sold in bags. One bag costs £49.50, including support from technicians.

As an estimate, one bag is required per 100 cows but this is dependent on farm size, cleanliness and the severity of the fly problem.

Bags need topping up every two weeks.

Walk-through fly traps

They are relatively uncommon in the UK, but are widely used on cattle farms in the USA.

Cattle walk through a structure with walls and a roof: the wall contains traps and flies are collected directly from cattle as they pass through the funnel (using dark-coloured brushes to force the flies towards the light of the roof) and they become trapped inside a false ceiling within the structure.

Other options include a vacuum method that blows air to dislodge flies from animals as they walk through the structure and flies are then sucked into the machine.

Effectiveness 

Repeated use of a mechanical trap can reduce the overall local population of horn flies.

Pros	Cons
A non-chemical method of control	Cattle must be “forced” to pass through a walk-through fly trap regularly, so it may be effective only where cattle are being handled regularly

Cost

These are typically home-made constructions, so the cost depends on materials used.

Stockholm tar

The product is applied to the udders and flanks of susceptible animals.

Effectiveness

A well-proven fly repellent for the prevention of summer mastitis.

Pros	Cons
Provides a physical barrier to flies Natural product	Can be used only on non-lactating animals No control against attack to the head and body of the animal Messy to apply The tar must be applied regularly, every 4-7 days, which can be time-consuming, especially if animals are away from yards

Cost

About £19 for 1kg.

Cow brushes with insecticide applicator

Insecticide applicators are incorporated into cow brush frames. As the animal passes under the horizontal brush, insecticide is applied through nozzles on to its back.

Effectiveness

Application rates and timings are highly variable, which means flies often receive sub-lethal doses of insecticide and this can lead to resistance.

Pros	Cons
Cows love brushes Brushes can be sited either in buildings or on field sites	The legs of the animal receive no insecticide so this method is not effective against stable flies

Cost

A pair of manual brushes with an insecticide dispenser costs about £160.

Water sprays and misters

Very fine spray nozzles mounted above milking parlour doors deliver a clean water mist across the face of the door when necessary.

Effectiveness

Best results are achieved when water misters are used in enclosed collecting yards.

Pros	Cons
Total water requirement is modest owing to the fine droplet size	The physical barrier is effective over short time periods Flies on the underside of cows are unaffected Operators will get a misting too

Cost 

Prices for farm power misters start at about £1,000, but cheaper alternatives can be sourced from Amazon – or made by drilling holes into alkathene pipes and feeding them with running water.