Start earlier to stay in control (Oct 26)
This year’s extended fly season has highlighted the hidden costs of fly pressure, but the problem may start long before flies become visible around the milking herd.
TEXT GEORGIE SAVERY
Fly pressure arrived earlier and persisted for longer on many dairy units this year, with sustained warm conditions providing an ideal environment for populations to build.
And Kingshay’s Sarah Bolt says this season should prompt producers to reconsider both when they start fly-control programmes and where to focus their efforts.
“While May to August is traditionally considered the main period of fly activity, producers should take a longer-term approach, monitoring for fly activity and potential breeding sites from early spring and maintaining control for as long as conditions allow populations to build,” she explains.
“This year, the warmer weather has accelerated flies' ability to reproduce. Once temperatures reach 30OC, breeding cycles can shorten from between 25 and 30 days to as little as six or seven days, which is why it’s essential to focus on managing breeding sites.”
Flies often start breeding in calf-rearing and housing areas, where straw bedding, manure and milk spillages create warm, damp conditions for larvae to thrive.
This makes calf housing an important area to consider when assessing fly risk, particularly where straw bedding is used and organic material can accumulate.
Quickly spread
Once flies reach adulthood, however, the problem can quickly spread beyond these initial breeding areas. “Adult flies will move towards milking parlours where they’re attracted to the warmth generated by large numbers of cows gathered in one place,” says Ms Bolt.
This is a particular risk for autumn-block systems, where at least 70% of the herd calve between August and October, as fly populations will have built throughout the summer.
“The increased use of calf pens creates additional breeding sites for flies to lay eggs, adding fuel to the existing burden,” she says. “So it is vital to keep pens as clean and dry as possible, with bedding and manure removed regularly. Cleaning and disinfection between animals can also help reduce the build-up of breeding material.
“Particular attention should be paid to the edges of pens and hutches, where larvae can develop unnoticed.
“Where pressure is particularly high, some pens may require cleaning almost weekly to help interrupt the breeding cycle,” she adds.
Breeding areas can be treated with an insect growth regulator to help control flies from the beginning of the cycle, reducing the number of flies reaching adulthood.
Adult flies
While tackling larvae can help limit the number of flies reaching adulthood, control also needs to extend to adult flies already circulating around the herd. “Once adult flies are present, it’s also important to consider where they land and rest,” says Ms Bolt.
“To tackle flies in the parlour, a spray can be applied to walls for control when flies land on the surface. Treating these areas not only helps reduce irritation to the milking herd, but also improves parlour working conditions for staff.”
Controlling flies at both the larval and adult stages is important because the consequences of rising fly populations extend well beyond irritation. Reduced feed intake can affect performance, while the spread of disease and infection creates additional labour and cost pressures for producers.
“Research shows that cows irritated by flies have a 13% lower feed conversion rate and 3% lower milk production compared with those where flies are managed well,” says Ms Bolt.
Beyond irritation, she says flies can also spread conditions such as New Forest eye and summer mastitis.
“If a milking quarter is lost due to mastitis infection, producers could be losing a quarter of that cow’s milk production, while increasing her chances of being culled from the herd,” she says.
“Premature culling then creates the need to rear or purchase replacement animals.”
Shift focus
Despite these potential costs, Kingshay’s research suggests there is still some way to go in shifting from a reactive approach, where producers treat visible adult flies, to a preventive approach that targets flies earlier in their lifecycle.
“Our recent survey showed that 92% of producers were using pour-on or spot-on fly treatments on milking cows, compared with around 70% on youngstock,” says Ms Bolt. “More than 60% considered pour-on the favoured option. This is what we’re trying to change.”
She stresses that the aim is not to replace effective animal treatments, but to complement them by reducing the number of flies that producers need to control in the first place.
“The key is to consider the whole fly lifecycle,” she says. “Treating the areas where fly larvae develop, or where adult flies land, can significantly curb the rate at which flies can breed, keeping populations under control from the beginning of the season.”
Taking that whole-lifecycle approach earlier in the year is one of the key lessons that producers can carry into next season. This year has shown that fly control needs to begin earlier and continue for as long as conditions allow populations to build.
“Don’t rely on one method of control,” adds Ms Bolt. “Use an integrated approach that combines good hygiene, environmental treatments and appropriate animal control.
“Identify breeding hotspots early, keep pens clean and dry, and tackle larvae before they develop into adult flies.
“Keeping fly numbers low from the outset gives producers a much better chance of staying in control when pressure increases later in the season.”
For producers planning ahead, this season provides a useful opportunity to identify where fly pressure started, which areas were most affected and whether breeding sites could have been tackled earlier.
Three steps to successful fly control
Effective fly control is about tackling the problem throughout the fly lifecycle, according to Lodi UK’s Ross Goodman.
“Combining good hygiene with larval and adult fly control can help producers to reduce populations before they become a significant problem.”
He urges producers to keep on top of hygiene. “Keep calf pens clean and dry, remove spilt milk and manure, and pay particular attention to pen and hutch edges where larvae can develop unnoticed.”
It’s also vital to target larvae early. “Use a larvicide product, such as Lodi UK’s Maggots or Larvenol, to target developing larvae in breeding areas before they reach adulthood,” he says.
“And control adult flies. Where adults are already present, Ultra Dairy Fly Spray can be applied to suitable surfaces, including walls, roofs and resting areas in parlours, providing knockdown and residual control.”
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