Flies are having a party right now… and the cows aren’t invited
If it feels like we’ve gone from soaking wet to sticky and humid in about five minutes — you’re not imagining it. And unfortunately, that combo is basically a VIP pass for flies and mozzies.
This is the time of year when we often see fly pressure ramp up on NZ dairy farms, and it’s not just “a bit annoying”. Flies can really mess with cow comfort, grazing time, and milking behaviour.
If flies are building, the cows usually tell you before anything else does:
Stomping and kicking (especially in the paddock)
Tail swishing non-stop
Bunching up in corners or standing in tight mobs
More restless in the shed (cups getting kicked off, fidgety milkings)
Less settled grazing — they’re busy avoiding bites instead of eating
When cows spend more time fighting flies than eating and resting, it can show up as lower production and more stress.
The main culprits right now
Stable flies (the biting “nuisance” fly)
These are the ones that really make cows miserable. They bite, and the cows react hard — stomping, bunching, and generally being hard to manage.
The annoying part is that stable flies don’t just come from nowhere. They breed in rotting organic matter around the farm.
Hotspots to check:
Silage pit edges (especially damp, rotting areas)
Waste feed / old baleage
Wet bedding / manure build-up
Feed pads and loafing areas where stuff stays soggy
If it’s been wet and things are staying damp, those breeding sites can crank out flies quickly.
Mosquitoes (including Culex)
After rain followed by humidity, mozzies can lift fast and they love anywhere water sits. Trough areas are worth a look (and anything that becomes a “forever puddle” around yards).
Blowflies
These tend to be worse in warm, humid spells too. On dairy farms it’s a reminder to keep an eye on anything that attracts them like wounds, dirty and soiled areas.
Practical stuff that actually helps (without making life complicated)
Here’s the quick checklist we recommend during these humid runs:
Clean up the breeding zones first
You’ll get more control by reducing fly factories than by chasing adult flies after they’ve exploded.
Silage edges and waste feed should be the priority
If it’s damp and rotting, it’s basically fly nursery territory.
Sort the soggy corners
Anywhere that stays wet around pads, yards, bedding and manure build up is worth attention.
Watch cow behaviour daily
If they’re bunching and stomping, fly pressure is already affecting comfort.
Where Fly Combo fits in
If you’re seeing flies lift in this wet/humid stretch, we recommend Fly Combo as part of your fly programme.
Fly Combo is simply added to the herd’s trough and includes support targeted at mosquito, stable fly, and blowfly, which covers the common mix we deal with at this time of year.
