With the days lengthening and the weather turning warmer, spring will happily soon be upon us. However, unfortunately that also means that fly season is on its way, with all the unwelcome irritation and nuisance that flies cause to livestock and the people that work with them:
The commonly seen nuisance and biting flies, such as head flies and horn flies (amongst others) can cause a number of issues for cattle:
Spread of bacteria that cause Summer Mastitis (the average cost of a case being £250-£300 – AHDB) and Infectious Bovine Keratoconjunctivitis (New Forest Eye/ Pink Eye)
Irritability in the milking parlour – kicking, tail swishing, dunging
Distraction from eating leading to reduced intakes and subsequently yield
Compromised cattle welfare due to constant irritation
In recent decades nuisance fly numbers have been controlled using insecticides such as Pyrethrins and Pyrethroids. Both in the form of aerosol sprays and topical solutions. However these chemicals are often fairly unpleasant to handle, and can be quite hazardous to the people using them. Particularly when spraying large quantities around the parlour. There is also evidence that resistance can develop in fly populations to some of these chemicals. This means that their effectiveness may decrease over time.
But there are alternative approaches to fly control that can substantially and naturally decrease nuisance fly populations on farm. Yes, we’re talking about the fly parasites again! These little insects have been around in the UK for quite a number of years now, but are still somewhat unheard of in the agricultural industry. (Maybe not amongst LLM, we’ve spoken a lot about these over the years. A little reminder each year will help jog memories we’re sure!)
These tiny insects are natural parasites of our nuisance fly species. They are used commonly in the poultry industry as part of biological integrated insect control programmes.
The fly parasite lifecycle
The process starts when the female parasites lay their eggs in the pupae of developing nuisance flies. The eggs then hatch and feed on the dead fly larvae before emerging and going on to parasitise many more nuisance fly pupae in the same way. Each female is capable of parasitising up to 350 nuisance fly pupae every day. So when you take into account that approximately 85% of all the flies on a farm are in developing stages (pupae and maggots), it makes a lot of sense to stop them there at source rather than killing them as adults using insecticides. By the time an adult fly lands on a cow treated with a topical fly product and is killed it may well already have laid hundreds of eggs, perpetuating the fly problem.
But of course, as with any biological control, it takes time for results to show. The life cycle of the fly parasites takes around 18-28 days. Whereas the life cycle of the nuisance flies takes somewhat less time and is completed in two weeks. This is why we recommend thinking about fly control now rather than when flies start to hatch. It becomes harder to stay on top of the population. Additionally, for the first few years it is beneficial to use in conjunction with more traditional approaches; as well as focusing on farm cleanliness.
With parasites, the greatest benefits are seen when they are used regularly. This allows a build-up of parasitic flies and suppression of breeding numbers of the nuisance flies. One study conducted in Argentina recorded a 90% reduction in fly population when compared to untreated control farms!
So there are definitely a lot of benefits to approaching fly control early and taking time to look at different approaches. Whilst there is clearly a cost to obtaining and distributing bags of fly parasites every fortnight throughout the summer months, this is offset by potential savings on other products.
However the real saving, although more difficult to quantify, comes when cow health and welfare is considered. For example, even one case of summer mastitis being prevented can save hundreds of pounds in addition to helping to reduce the overall amount of antimicrobial usage on farm, and the extra time spent eating rather than moving around to avoid flies increases overall yields. This is definitely an approach worth considering if you struggle every year with fly problems.