Horse owners urged to mow before they harrow to control worms in hot weather
Mowing before harrowing is key as this summer’s high temperatures have created a “rare opportunity” to help manage parasites
Horse owners are urged to mow before they harrow, as this summer’s high temperatures have provided a “rare window” for effective worm control.
Parasitologist Diane Gilby, founder of Intelligent Worming, which creates individual equine parasite control programmes, has put together evidence-based guidance for owners. She said the critical step is mowing before the harrow goes in.
“Everyone knows you should harrow in hot, dry weather. What almost nobody talks about is the height of the grass,” she said.
“If the sward is above 15–20cm, the canopy creates shade and traps moisture at ground level, which is exactly where the larvae concentrate. You end up spreading viable parasites under a grass canopy where UV cannot reach them. You have made the problem worse, not better.”
Research has found that grass must be cut to below 10cm to ensure faeces broken up by the harrow is exposed to sunlight and air.
Having considered the findings from peer-reviewed studies, Ms Gilby recommends a specific procedure. When at least five consecutive days of hot, dry and sunny weather is forecast, fields should be topped so the grass is below 10cm in height, and all horses removed before the harrow goes in.
Paddocks should then be rested for at least a week before horses return, although a longer break is more effective. Fields should not be harrowed if rain is forecast within three days, the temperature is under 25°C or in overcast, humid conditions. If the grass is over 15cm tall and cannot be mowed first, these fields should also not be harrowed.
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Eleanor is an experienced journalist who spent over eight years working for local and national newspapers before joining H&H as news editor in March 2016. Passionate about equine welfare and exposing the truth, Eleanor has reported on all aspects of the industry, from Brexit to anti-bullying campaigns, and from dressage rules to mules. Her sport of choice is showjumping, in which she competes her own horses, and she also enjoys reporting at local jumping shows through to international championships.