Effective Fly Control Ensures Cattle Can Keep their Noses to the Ground

The season for cattle flies can start as early as April in some areas, which is important as flies can cause significant production losses for dairy and beef cattle.

Flies are more than just a nuisance for both livestock and people causing irritation, stress and serious effects on productivity via reduced weight gain and reduction of milk yields. Flies are also responsible for the spread of significant cattle diseases such as summer mastitis, salmonella and New Forest Eye (Moraxella bovis).

The most common species of flies that affect the productivity of cattle are:

Non biting flies
House Flies (eg Musca domestica) and Face Flies (eg Musca autumnalis) – these flies do not bite, but they breed easily in manure, quickly forming large numbers which can cause great irritation and transmit diseases. Animals that are distracted by flies will graze less and hence not perform as well. Treating animals and fly breeding sites will help to minimise any potential losses associated with nuisance flies.

Biting flies 
Horse Flies (eg Tabanus sp.) and Stable Flies (eg Stomoxys calcitrans) – unlike the similar looking house flies, Stable and Horse flies deliver extremely painful bites, with both males and females feeding on blood.

Horn Flies (eg Hydrotea irritans) – these blood sucking flies also look similar to house flies, are extremely irritating and can cause production losses.


The relatively mild winter has potentially failed to kill off over-wintering fly populations – so much so that as the weather warms up there could be an explosion in insects that both irritate ruminant livestock and transmit diseases.

Climate change is also influencing the way entomologists and animal health experts think about fly control, and preempting the threat this year to your livestock can go some way to reducing potential insect-borne disease problems later in the summer.

Early insecticide treatment of cattle can help reduce insect populations. Applying a proven insecticide early in the season will both reduce the first wave of attack from biting insects and cut next generation numbers. If you can kill flies early or even stop them feeding on your livestock, you will reduce their ability to breed.

Seeing flies or midges on or around animals are usually the main triggers for applying insecticides, but significant insect populations can have built up by then. And left untreated, an insignificant early season insect population can become a huge one in just a few weeks. The main objective is to kill as many insects as possible when the first landing parties arrive on your livestock to feed.

As well as treating cattle early, it’s also important to keep on top of the insect problem as we move through the warmer months. A mixture of different fly and midge species threaten most farms with populations peaking at different times and waves of attackers hatch out to trouble herds all season long. So in addition to applying insecticides, aim to reduce potential insect breeding sites and consider housing livestock at dawn and dusk if insects are particularly active.

Did you know?

  • It only takes 10-20 head flies to have a negative economic impact on farm.
  • The horn fly will feed on blood from cattle up to 40 times per day – this could lead to blood loss and constant irritation for the animal. 

The risk of not treating flies and external parasites on cattle and sheep:

  • Reduced milk yields of up to 20% (1)
  • Increased incidence of summer mastitis
  • Reduced calf weight gain
  • Downgraded wool quality
  • Reduced reproduction in sheep
For more information contact dairy@wynnstay.co.uk

(1 – Taylor. B.D. et al. Economic Impact of Stable flies (Diptera Muscidae) on Dairy and Beef Cattle production. J. Med. Entomol 2012, 49)

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