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Ask a Vet: Fly control

Jim Heier for Progressive Dairy Published on 28 June 2019

The problem

Flies can be costly to dairy farmers due to disease transmission and irritation. Whether feeding upon animals or simply being a nuisance, flies can reduce milk production and decrease weight gains.

There are a number of quality fly control products; however, extended use of one product will cause flies to develop a resistance over time, and the product will become less effective.



The best way to control flies is through the implementation of an integrated fly control program.

Your solution

An effective fly control program uses a combination of products (larvicides and adulticides) that attack different types of flies at different stages of the fly life cycle with various environmental, biological and chemical techniques.

When choosing a product that’s best for your operation, it’s important to know what type of insect is controlled or reduced with use, what stage it’s in and which technique to use:

Types of flies

face flyFace fly (Musca autumnalis)

  • Non-biting fly; measures 
    6 to 8 millimeters

  • Direct transmitters of pinkeye 
    in cattle

  • Larvae grows in freshly deposited 
    cattle manure

horn fly


Horn fly (Haematobia irritans)

  • Blood-feeding fly; measures 
    4 to 5 millimeters

  • Stays on cattle after feeding

  • Moves to the underside of cattle 
    during rain and hot temperatures

  • Carries diseases that decrease 
    weight gain and lower milk 

  • Larvae grows in cattle manure 
    (does best in grass manure of 
    pastured cattle)

stable fly

Stable fly (Stomoxys calcitrans)

• Nuisance blood-feeding fly; measures 
6 to 8 millimeters

• Interrupts cattle’s normal feeding 
and resting activities

• Larvae grows in wet manure mixed 
with soil, straw, bedding material, 
silage or grain


house fly

House fly (Musca domestica)

• Non-biting fly; measures 
6 to 9 millimeters

• Most abundant insect associated 
with cattle but causes the least 
amount of harm

• May cause ear flapping, head 
shaking or pen avoidance

• Larvae grows in virtually all 
substrates including feed, manure 
and vegetation

horse fly

Horse fly (Tabanus lineola)

• Bloodsucking fly; measures 
19 to 25 millimeters

• Numerous painful bites can 
cause a significant loss of blood

• Larvae grows in mud along pond 
edges, stream banks, wetlands or 
seepage areas

Fly stages

  • Larvicides – Insecticides targeting the larvae stage of a fly (Larvicides come in a variety of forms including biologicals, baits and feed additives.)

  • Adulticides – Insecticides used to kill adult flies (Adulticides are available in baits, sprays, pour-ons and traps.)

Fly attack techniques

  • Environmental – The proper management and sanitation of manure, feeds and facilities

  • Biological – Enhancement of the naturally occurring populations of fly predators and parasites

  • Chemical – Pour-ons, sprays and baits used in conjunction with environmental and biological techniques to achieve desired degree of fly control (Rotate yearly to avoid resistance.)

Ask your veterinarian if you need assistance developing a comprehensive fly control program.  end mark

Jim Heier
  • Jim Heier

  • Professional Services Veterinarian
  • Animart
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