Horse Fly Sheet - Fly Rugs - Fly Masks

Fly sheets, rugs and masks are one of the 10 Solutions to Horse Flies.

A horse fly sheet covers the body of a horse, to protect it from flies and in particular from biting insects. Some people use the term 'horse fly rugs', which means the same thing, although this name is somewhat misleading as the product is in the form of a sheet (e.g. thin mesh) rather than a rug.

The topics covered in this article are:

  • 1.0 Benefits of Fly Sheets
    • 1.1 Disadvantages of Fly Sheets
  • 2.0 Types of Fly Sheets
  • 3.0 Types of Material
    • 3.1 Durability
  • 4.0 Sizes
  • 5.0 Choosing a Fly Sheet or Mask

1.0 Benefits of Fly Sheets

A fly sheet serves multiple purposes:

  • Horse comfort - biting flies. By protecting the horse from biting flies, it allows the horse to be more comfortable and reduces stress. If the horse is pastured in an area where there are a large number of biting flies, this is particularly important not only out of kindness to the horse, but for the practical reason that a highly stressed horse has less resistance to certain illnesses than a relaxed horse.
  • Horse comfort - non biting flies. Even non-biting flies, such as the common house fly, can be an annoyance to horses. This is particularily so when they cluster around the sensitive eye areas.
  • Diseases. There are a number of serious infectious diseases which are spread by biting flies. Fly sheets provide partial protection, by reducing the number of fly bites.
  • Eye infections. Eye infections can be caused or spead by flies (including house flies) that enter the moist areas around the eye. The use of fly masks can greatly reduce this risk.
  • Insect repellants. The use of insect repellants can become expensive, if your horse requires these products for extended periods. Furthermore, there are a number of concerns over the possible long-term side effects of repellants, which are absorbed through the skin into the body. A fly sheet offers an alternative, which avoids the possible risks associated with chemical insect repellants and can be cheaper in the long run. With our horses, we found that the savings in insect repellants over the course of a single summer paid for the cost of buying fly sheets for our horses.
  • Secondary benefits. Although not the main purpose of a fly sheet, there are two additional potential benefits.
    • Sun protection. A fly sheet can also offer protection from sun burn, for horses with pale coats or sensitive skins. It can also help to prevent bleaching of the coat by the sun. In both cases, only the areas covered by the fly sheet will be protected. Furthermore, depending on the type of fly sheet (e.g. open mesk or solid) and the sensitivity of the horse, the sheet may or may not provide sufficient protection from the sun for sensitive horses.
    • Dust and dirt. Like any cover, a fly sheet will help keep dust and dirt off of the horse's coat.

1.1 Disadvantages of Fly Sheets

The most common complaint about fly sheets is that they rip (see section 3.1 for discussion) or may not fit the individual horse (see section 4.0).

Another problem, fortunately uncommon, is that not all horses will accept fly sheets or masks. The vast majority of horses will wear them comfortably, after a few hours or days to get used to them. In fact, many horses soon learn that the sheet and masks will protect them, and I've known horses to run away if their owners tried to remove this protection while there were still flies about. However, the occassional horse does not get used to them and will either try to remove them (sometimes damaging them in the process) or will show signs of stress. This appears to be more of a problem with fly masks than with fly sheets due to the visibility problem.

One of the special problems with fly masks is that they reduce visibility. Horses are more sensitive than people to obstructions in front of their eyes (perhaps due to their differing eye placement). The reduced visibility can cause stress as the horses feel they can no longer see potential threats as well. This problem is worse if the masks become wet or dirty, further reducing visibility. When approaching a horse with a mask, it is best to start talking some distance away so that the horse can hear you and know that you are there., to avoid startling the horse who may not see you until you are very close.

When putting fly sheets on a group of horses for the first time, there can be social issues and even aggression because the horses may not recognise each other any more. Consequently, fly sheets and masks should be gradually introduced to a group. For example, rather than put the entire outfit on at once, use just the fly sheet until they get used to it and then add the fly mask. Once the horses become used to the sheets and masks, they learn to recognise and accept each other when wearing them; this can take anywhere from a few minutes to a few hours (in exceptional cases, a few days).

As fly sheets are worn mainly during warm weather, they are typically white or silver so that they reflect the heat of the sun. Be wary of choosing dark colours, as this can result in overheating of the horse. There is some dispute as to whether the insulation provided by the fly sheet increases the horse's temperature or if the reflective white/silver colour actually protects it from the heat. This is further complicated by the fact that the type of material the fly sheet is made of (see section 3) affects the extent to which heat is retained. In any case, we would advise that on hotter days, the horse owner should ensure that the fly sheet is not overheating their horse.

2.0 Types of Fly Sheets

There are several elements to a fly sheet:

  • Basic fly sheet. This covers the back and sides of the horse, with straps to hold it in place.
  • Belly panel. Many fly sheets have a panel or flap which covers the belly of the horse. This may either be part of the fly sheet itself, or may be removeable (e.g. can be clipped or unclipped).
  • Neck cover. This covers the neck of the horse. It may be a part of the fly sheet itself, or a removeable piece which can be attached or detached from the main fly sheet.
  • Fly mask. This covers part of the head or face of the horse; in particular it covers and protects the eyes, and usually covers the ears (the soft inside of the ears are a target for certain types of flies). The term 'fly bonnet' or 'riding mask' (as a horse is easier to ride when it is not distracted by insects on its eyes, ears and face) are sometimes used instead of 'fly mask', but they are the same thing.
  • Tail cover. Some fly sheets also have a piece to cover the tail. This is particularily of benefit in protecting the horse from the small fly which causes 'summer eczema' in the mane and tail areas.

The following pictures illustrate different elements and some of the combinations for fly sheets:

Body Body with Detachable Neck Integrated Neck, with Tail Cover
 Fly sheet 3  Fly Sheet 2  

These pictures are examples of different types of masks. Some masks are designed to be used on their own, while others are designed to be attached to a bridle (these, in particular, are often known as a 'riding mask'). 

Mask - Full head  Mask - Partial head, bridle attached  Mask - Partial head, no ears
Fly Mask 1  Fly mask 2  Fly mask 3

3.0 Types of Material 

 Fly sheets (and masks) vary not only in terms of how much of the horse is covered, but also in terms of the material and construction:

  • Construction. The construction can be webbing, mesh or solid. A solid mesh provides the greatest protection from insects and sun. Webbihas better air circulation to the skin and less insulation, both of which are advantages on hot summer days. Mesh construction lies between the other two on these measures. See photos below.
  • Thickness. Different manufacturers use different thicknesses of materials. Thicker fly sheets offer more protection (some large biting insects can penetrate the thinner materials), while thinner sheets offer more flexibility and are less likey to cause overheating of the horse on hot days.
  • Durability. Depending on the type of material and construction, some fly sheets are more durable than others. See section 3.1 for further information.
Webbing Mesh Solid
Fly Sheet Material 1 Fly sheet material 2 Fly sheet 3

3.1 Durability 

Perhaps the most common buyer complaint about fly sheets is the material ripping, in some cases shortly after purchase. In some cases the actual material rips, while in others there is separation at the seams. The probability of a fly sheet ripping is dependent on a number of variables, only some of which are related to the fly sheet itself. Consequently, some horse owners have trouble with brand A but not brand B, whereas others have the opposite experience (trouble with brand B but not brand A). Although certain brands will be of higher quality, the lack of consistent results makes recommendation of specific brands difficult. Factors which determine how long a fly sheet will resist ripping include:

  • Amount of Use. A fly sheet which is left on a horse 24-hours a day will tend to suffer more wear than one which is used part time or only for certain days.
  • Sharp Objects. If there are objects (sharp or even not so sharp) which the horse rubs against, this may tear the fly sheet.
  • Horse Behaviour. The behaviour of the horse is a major factor in determining how long the fly sheet will last. A horse which quietly stands in its pasture is unlikely to damage the sheet, whereas one that rolls or even actively tries to remove the sheet (or mask) is much more likely to cause damage (tears, separation at seams, or damage to straps). To complicate matters, a given horse may not react the exact same way to all fly sheets. For this reason, a light and flexible fly sheet which the horse does not mind may survive longer than a stronger fly sheet which the horse actively tries to remove.
  • Size. A fly sheet which is too small for the horse is more likely to rip, especially with active horses. One that is too large may also be more damage prone, if the horse can become tangled in the material or straps.
  • Shape. Horses vary not only in size, but also in body shape. A racing horse and a draft horse may have the same size in terms of height or length but will have completely different shapes. A fly sheet needs to fit not only in terms of size but also in terms of shape if the risk of damage is to be minimised. See section 4.0 below for further discussion.
  • Fit. A fly sheet needs to be properly attached, with the straps loose enough that the horse can move within the sheet without straining it, but tight enough that there is no risk of tangling. The straps around the back legs are usually the ones that are most difficult to adjust correctly.
  • Thickness. A thick sheet will have more strength than a thinner sheet. However, some horse owners find that very thick sheets are inflexible, which can increase the risk of ripping.
  • Material and Construction. Materials vary in terms of strength and flexibility, both of which affect durability. There are also different types of construction (e.g. number of seams, types of seams, location of seams).

As a result of these variables, there is great variation in how long fly sheets last in practice. On one hand it is not uncommon for fly sheets to be ripped within a couple of weeks of use, while on the other hand many buyers find that it lasts the entire year (which is just a few months, depending on how long the biting insect season is) or even multiple years.

The use of a repair kit to fix tears as soon as they happen, before they become larger, can greatly extend the useable life of a fly sheet. Depending on the location and severity of damage, as well as the type of material, it is usually possible to repair small rips oneself. Many manufacturers of fly sheets can provide a repair kit for this purpose. You may wish to ask about this before ordering a fly sheet, as it is preferable to purchase a fly sheet that can be repaired rather than one that cannot. When buying a fly sheet, it may be cost effective to order a repair kit at the same time as they normally are not expensive and you can avoid the additional charges of postage and handling associated with ordering it separately at a later date.

4.0 Size

Fly sheets come in a number of sizes, normally based on the length of the sheet. The width is of secondary importance since the sheet lies loose down the sides of the horse. For ordering purposes, one needs to know how the individual fly sheet manufacturer measures length. The common method is to measure from the centre of the chest to the middle of the bum, as measuring in this way will take into account somewhat the breadth of the horse. Although individual manufacturers may specify at what height the measurement should be done, in our experience it is best to do this at the widest point (i.e. at the chect height giving the longest length when measured in this way), using the same height for both ends of the measurement.

When producing the fly sheet, each manufacturer chooses a sheet shape based on the general shape of the horse. For example, a fly sheet with an attached neck piece must base the neck cover on a certain neck thickness and length. However, horses are not all the same shape, so individual fly sheets do not always hang or fit well on the horses for which they are intended. Furthermore, as different manufacturers use somewhat different shapes for the fly sheet patterns, for one horse brand A may fit better than brand B, while for another horse brand B may fit better than brand A. Consequently, it is preferable if you can try before you buy.

For fly masks, the way in which the measurement is done will depend partly on the type of the mask (e.g. full head or partial head, independent or bridle attached). Check with the individual supplier when choosing a size.

The mask edges need to fit closely around the head, to prevent flys entering the mask under the edges. To prevent this, one must ensure both that the mask is not too large and also that when it is put on the horse the straps are adjusted for a close fit (most fly masks have velcro attachments for this purpose). However, one must ensure that it is not so tight that it causes discomfort to the horse or that it chaffs the horse.

When ordering a fly mask, one should be aware that certain fly masks are made of soft materials which can stretch with use. For such masks, it may be best to order slightly on the small side and let the velcro straps out slightly until the mask stretches. Otherwise, one risks ordering a mask which after a couple of months is too large to provide a snug fit.

5.0 Choosing a Fly Sheet or Mask

As discussed above, there are many different variables to fly sheets (e.g. material, thickness, which parts of the horse are covered). Selecting each of these different items correctly requires consideration of both your objectives and the nature of the horse. One of the major considerations is the type of flies that you are trying to protect the horse from:

  • Summer eczema or 'sweet itch'. The insects which cause this problem bite mainly in the mane and tail. To prevent this you need a fly sheet which has a neck piece and covers the top of the tail. A fly mask is not required. As the flies are small, a light mesh will be sufficient to prevent them from biting.
  • Horse flies. These insects will bite almost all parts of the body, so one needs to cover as much as possible (neck and belly) but it is not neccessary to cover the tail. A simple mesh should be sufficient to stop them from bithing.
  • Mosquitos. Like horse flies, they will bite almost any exposed area so maximum coverage is best. A mesh is likely unsuitable as the 'needle' which they use to bleed the horses can fit into the mesh holes, so a solid fly sheet is more suitable.
  • Large biting flies. The largest biting flies can actually bite the horse through light fly sheets, so a heavier fly sheet is needed to provide protection.
  • House flies. House flies are mainly an issue around the eyes, followed by the nose. Consequently, a fly mask is the best protection.

One also needs to consider factors such as temperature (thick sheets may be unsuitable in very hot temperatures), durability (a thick but flexible material is best), use (a stand alone mask for pastures or one suitable for riding out) and quality of manufacture (in terms of material and seams).

To ensure a correct size and fit, the option to try before buying is preferable.