Fly Control Strategies on Dairy Goat Farms

High fly populations can be an irritant for animals, farm workers and neighbours. With livestock, flies can cause reduced feed intake, negatively affecting weight gain and milk production. Flies can also spread bacterial and viral diseases. For example, bacteria that cause mastitis can be transferred from the teats of an infected doe to a healthy doe by flies and fly bites. There is no magic bullet for fly control but good management and a multi-pronged approach will result in more productive goats and happier dairy goat farm workers.

The Pests and Their Biology

Fly Life Cycle

Figure 1: Fly Life Cycle

The most common types of flies found on dairy goat farms are the stable fly, house fly, and sometimes fruit flies. The stable fly has piercing mouth parts (in other words, they bite). Both male and female stable flies feed on blood several times a day, normally attacking the legs and belly. Stable flies take about three weeks to develop. The stages are egg, larva (also known as maggot), pupa to adult. Adult female flies can live 30 days and lay up to 400 eggs. Stable flies breed on organic debris such as: wet straw, manure and spilled feed.

The house fly is non-biting. House flies breed in organic matter such as bedding, manure decaying silage, and spilled feed. During warm conditions they can complete their life cycle in just ten days!

Control Options and Tools


Keep all areas of the barn clean. Insecticides cannot be expected to control flies under poor sanitary conditions. Some producers spend too much money on insecticides and ignore that flies require moist organic matter to reproduce. The immature fly takes ten to 21 days to develop. Cleaning goat pens weekly helps break the fly's life cycle. Attention should be given to the perimeter of the pens and area around water bowls, as more maggots are often present at these locations. The drying action of desiccants such as Dry Start or Stalosan spread after pen cleaning can play a role in reducing fly populations. These desiccants also reduce manure odours which attract flies. It is important to not overlook the kid pens. The kids are on high liquid diets and thus excrete more liquid making these pens a perfect area for fly reproduction. Eliminate spilled feed, rotting hay and moist decaying organic matter, repair any water line leaks, and keep vegetation around the barn and manure pile well mowed to reduce areas where flies can rest.

The importance of good sanitation in controlling fly populations cannot be over emphasized. In addition to pens, keep the entire milking parlour and milk house as clean and fly free as possible. This includes in and around the drain and receiver jar of pit parlours. Tight-fitting, self-closing doors and screens are required. The entire floor surface needs to be kept clean including under the bulk tank, the drain and area close to the drain, floor areas along walls and in corners, around cleaning chemical containers, etcetera. If milk replacer is mixed in the milk house, any spills need to be cleaned up promptly. A poorly rinsed milk filter can attract flies often making garbage cans the perfect reproductive site for flies. Empty the garbage container frequently and clean the garbage can. Small fruit flies can also be a serious issue in a milk house since they are small enough to get into the bulk tank - particularly flat top tanks. Bulk Tank Milk Graders grade milk tanks by sight and smell and have rejected tanks with flies including fruit flies. Sanitation is the key to keeping fly populations under control.

Mechanical Control

Sticky tape and traps can play a role in controlling small or moderate fly populations. A clean, well-managed milk house may only require sticky tape for fly control. Sticky rope placed above a highline pipeline (a warm area where flies congregate) will help. Electronic fly zappers are a onetime cost and can help in localized areas.

Screens and tight-fitting, self-closing doors in the milk house are regulatory requirements for a good reason - they limit entry of flies into the milk house. Using large fans to circulate air in the milking parlour and animal housing areas makes conditions less favourable for flies by preventing them from resting and helping to dry damp areas.

Chemical Control

Always read and follow product labels. Some fly control products require Ontario Pesticide Certification. For more information on Ontario Pesticide Certification you can visit

Baits are useful in controlling moderate fly populations. Baits need to be put in shallow dishes or mesh bags rather than spread directly on the floor, window sill or milk stand. This will prevent possible cross contamination of milking equipment or milk.

Space sprays provide a quick knockdown of flies in an enclosed air space. Space sprays have little residual activity; therefore, flies usually do not develop resistance and remain susceptible to them.

Residual sprays are fly control products typically applied to walls, posts and other fly resting areas. Flies can develop resistance to residual sprays so they should be used with caution and only when outbreaks cannot be managed by other techniques. Rotation of pyrethroid and organophosphate products can reduce the potential development of resistance.

Consider Biological Control

Flies have natural enemies such as parasitic wasps that can be used to biologically control fly populations.

Parasitic wasps find and kill fly pupae. However flies have some reproductive advantages over the wasps. Flies develop twice as fast from egg to adult, live longer and lay more eggs. Fly populations also begin to grow earlier in the spring than the wasp population. Therefore to be successful as a biologic control, natural populations of parasitic wasps need to be enhanced by frequent releases of large numbers of commercially available parasitic wasps. Note that parasitic wasps should only be one part of the farm fly control program.

Ontario Companies that Supply Parasitic Wasps

  • Bugs for Bugs - Guelph, ON 519-836-8166
  • Koppert Canada - Scarborough, ON 416-291-0040
  • Natural Insect Control - Stevensville, ON 905-382-2904

For more information:
Toll Free: 1-877-424-1300