Farnam Endure Fly Spray Review: Does Sweat-Resistant Really Last?

The fly spray that survives a sweaty horse, in the size that makes daily use affordable.

The verdict: A broad-spectrum sweat-resistant fly spray in a gallon refill, which is how you buy fly spray if you actually use it every day rather than occasionally. Buy it if your horse works or sweats in hot, humid conditions where ordinary sprays wash off by mid-morning. Be sceptical of the 14 day claim, which describes ideal conditions rather than a horse living outdoors in summer, and consider a fly sheet, which does not wear off at all.

Specifications

Specifications above come from Farnam's published specifications. Treat pricing as approximate, since Amazon pricing moves.

What it does well

• Sweat resistance is the specification that separates fly sprays that work on a working horse from ones that do not. Most sprays fail the moment the horse sweats.
• Broad spectrum across the species that actually bother horses, including the biting flies that cause the most distress.
• A gallon refill costs a fraction per ounce of the small spray bottles, which matters because effective fly control means applying it properly rather than sparingly.
• Rain-ready, which matters as much as sweat resistance for a horse living out.
• Usable on pasture horses and working horses alike, so one container covers a mixed yard.

Where it falls short

• The 14 day claim is a best case. A horse rolling, sweating, being rained on and rubbing against a fence will need it far more often than fortnightly, and treating the claim as a schedule leads to an unprotected horse.
• Any insecticide is a chemical applied to skin. Follow the label exactly, do not use it on broken skin, avoid the eyes and muzzle, and use gloves. It is not more effective at higher concentrations and it is more likely to irritate.
• Some horses react to fly sprays with hives or skin irritation. Test on a small patch first, especially on a senior with thin or sensitive skin.
• Repeated use of the same chemistry across a yard raises resistance concerns over seasons.
• Spray does nothing for the flies breeding in the muck heap. Fly control that works is muck management first, physical barriers second and chemistry third.

What owners report

Owner reports on Endure are consistent that it outlasts ordinary sprays on a sweating horse, which is the specific problem it is designed for. Reports of it lasting anything like two weeks in real turnout conditions are rare, and most owners describe reapplying every few days.

The recurring caution across all fly sprays is skin reaction in sensitive horses, which is worth testing for rather than discovering across a whole horse. Owners of horses with sweet itch or existing skin conditions consistently report better results from physical barriers than from any spray.

Who it suits

• Horses in work who sweat, where ordinary sprays disappear within an hour.
• Yards buying in quantity, where a gallon refill transforms the cost of daily use.
• Anyone in a hot, humid climate with a serious biting fly season.

Who should skip it

• Horses with sweet itch or sensitive skin, who usually do better under a fly sheet. Our fly sheet versus fly spray comparison covers why.
• Owners looking for a chemical-free approach, who should start with muck management and physical barriers.
• Anyone applying it to a horse with broken skin, wounds or an undiagnosed skin condition.

Alternatives worth considering

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• Horze Nevada turnout review

This review draws on published specifications, manufacturer figures and the consensus of verified owner reviews. We have not tested this product ourselves, and we say so rather than implying otherwise. As an Amazon Associate we earn from qualifying purchases.