Two-pronged approach for effective fly control

There are no flies on Richard Malpass – or his cows. Since splitting from a family partnership two years ago, he has set up a dairy farm on a two-million litre greenfield site where just two men will handle 200 cows plus followers with ease.

As well as efficiency and automation – there is auto ID, segregation and weighing – Mr Malpass was conscious that he was starting with a fly-free unit at Upper Cowley Farm near Gnosall, Staffs, and he wanted to keep it that way for himself, the cows and his staff, Paul Fenton and Sam Holroyd. He well remembers the nuisance of summer flies from his previous dairy farm.

“It was terrible – murderous in the parlour for me and the cows. We had a typical old-fashioned parlour with low ceilings and no airflow. Fly control was used on dry cows and heifers, but we never treated milkers. We often saw August bag in heifers at grass. Although it’s hard to quantify the problems that flies cause, there must be consequences if stock are irritated all the time,” he says.

Flies like to use spoiled silage, spilled feed and muck as breeding areas. With this in mind, as well as a desire to maintain top hygiene standards, Mr Malpass designed buildings that were easy to keep clean. “Being tidy helps a lot in fly control,” he says.

Clamps and muck storage were sited away from milking and housing areas. Slurry passages were made extra wide (15’) – easy to clean and cows don’t stand fetlock-deep in slurry – while the 20/40 parlour is light, open and airy and still cool enough without needing fans. Straw yards are cleaned out every three weeks, leaving no muck lying about. There are no parlour feeders to attract flies to dust or uneaten feed and the bulk tank room is windowless: “No windows means no sunshine and no flies,” he explains.

As high yielders will be housed full-time this year to maintain diet consistency (and low yielders housed by day when it’s hot and turned out at night when it’s cooler), Mr Malpass was particularly keen to keep the fly population to a minimum. Last year, he used Butox^® SWISH pour-on for the first time with success. “We applied it early before the peak fly problem to stop the population building up – which it did. It was very noticeable that we had no flies in the parlour, no kicking cows or clumps of flies on them.”

This year, two applications (8-10 weeks apart) will be combined with biological control, using natural fly predators added to slurry to kill house and stable fly larvae. This programme, drawn up by James Allcock of the Lambert, Leonard and May veterinary practice in Nantwich, arose because some large herds were spending over £1000 each summer on insecticides, yet failing to get effective control.

“We needed to look at improving our fly control recommendations because 85% of flies on farm are not adults, but in developing stages. Just focusing on killing adults can be a losing battle, so we think it’s better to go for an integrated approach, killing all stages in all places.

“Fly control is a two-stage process, which starts with managing maggots.  This is done biologically, using predators to eat them, or chemically with hormones that stop maggots from maturing to the next stage. The second stage involves killing any adult flies that do develop with a pour-on insecticide,” says Mr Allcock. 

Last year, he trialled the fly predators Muscidifurax raptor (which likes house flies) and Spalangia (it prefers stable flies). Farmer feedback was so good, there are now 10 herds using the system. These predator flies are indigenous to Britain, look like small midges, but are not attracted to humans or animals. Naturally, they live in balance with the fly population. Using them to control it, therefore, is all about the speed a fly egg takes to develop in summer and placing enough predators in the right location at the right time, says Mr Allcock.

“In summer, at 24C, it takes just 7-10 days for a fly to develop – so the fly population soon explodes. Unfortunately, the fly predator life cycle is rather slower at 30 days, but by releasing lots of parasites we can shift this balance.

In addition, house and stable flies will travel up to 10 miles, so they arrive from other farms. The parasite fly stays within a 10 metre zone. It travels to the next maggot in places where the flies breed: around the slurry lagoon, or anywhere muck is trapped in hard to clean areas.” 

Around 50,000 parasitised fly maggots are released on the farm for every 100 cows just as the parasites are hatching. The males emerge first, mate with the females which then go off to lay their eggs in fly maggots in slurry. The females sting and kill the developing fly and lay their eggs inside it. This becomes the food source for the developing predator eggs. The parasitised maggots are spread on farms fortnightly for the 3-4 summer months to keep numbers up. “Flies go into a sort of hibernation over winter and the predator flies do the same. This is why we have to add more. After a couple of years, however, the population should be such that we don’t need to introduce so many,” adds Mr Allcock.

At £40/bag for the predators, justifying the monthly 80p per cow (one bag per 100 cows per fortnight) can be hard to measure, he admits. On clean farms such as Upper Cowley, one pack will stretch to 200 cows so the cost halves to 40p per cow per month, plus any pour-on Mr Malpass uses. Without having had a previous fly problem at the unit it’s difficult to work out the payback. But Mr Allcock points out that apart from the human hassle factor, flies transmit diseases and cause an underlying reduction in cow performance.

Research from the US has shown that using fly predators can reduce the stable fly population by 25-50% and if the fly population is brought under control, the use of Butox SWISH will be even more effective, he says. “Work has also shown that calves bothered by stable flies see a fall in liveweight gain of 0.1kg/day. In replacement heifers, a reduction in growth rates can have knock-on effects delaying puberty and cutting milk yield in their first lactation. Whereas in high yielding cows, any fall in dry matter intake affects yield, body condition and fertility.”

Paul Fenton says Butox SWISH is easy to use, covers a larger area and is more effective than a spot treatment. “I’ve used spot treatments before which had to be applied three times and I don’t think they work half as well,” he says.

Paulmanages Richard Malpass’ 200 cows at Upper Cowley Farm, near Gnosall, Staffs and says June and July are peak fly problem months, particularly for biting flies. He applied Swish in mid May this year, on advice from the farm’s vet practice, and said he was able to do the whole herd while cows were laid in cubicles. “It took less than half an hour. The gun delivers six lines of insecticide across the cow’s back, and it spreads down their sides to give good overall coverage. It dries as a temporary white streak, so you can easily identify any cows you have missed.”