By the time you notice cattle or sheep being troubled by flies, a population explosion is already taking place.
However, thanks to “Professor Google”, it’s easy and cheap to make some fly traps (see instructions), then keep an eye on them every few days for an early warning that fly numbers are on the rise.
Zoetis vet, Aurelie Moralis, suggests that raw liver is suitable bait for the fly species that bother livestock.
To assist farmers in monitoring the fly population Zoetis has set up a “Parasite Watch” site on Twitter (@sheep_farmers) and various farmers throughout the UK are participating in order to assess the effectiveness of the scheme. Co.Down sheep farmer Crosby Cleland has undertaken the task for Northern Ireland and has already got his fly traps in place.
Aurelie Moralis, Veterinary Consultant with Zoetis said: “Parasite Watch, is the first scheme of its kind in the UK and farmers like Crosby, are an integral part of helping fellow farmers to make informed decisions on the potential parasite challenge on their farms. He will communicate the highs and lows of his lamb rearing season on our twitter site.”
Independent entomologist Dr Peter Bates of the Veterinary Medical Entomology Consultancy also advocates an early start before the insect breeding season pointing out that it gives the best chance of minimising the annual population explosion of flies and midges that begins as soon as average daytime temperatures reach 10°C.
He adds that delaying the start of control measures can mean playing catch-up and usually losing, and warns against assuming that winter frosts – a rare thing anyway so far this winter – will help reduce the coming summer’s insect populations.
“Even if air temperatures are below zero for several days running, the larvae of some species relevant to livestock overwinter typically about 10 centimetres below the soil surface where frost may not penetrate,” he says. “So this cannot be relied upon to kill insect larvae.
“Moreover, larvae of some species overwinter in woodland litter, where frost penetration is quite rare no matter how cold the weather. Then as soon as they hatch from pasture or woodland, bloodsucking species can migrate several kilometres to find livestock on which to feed.”
While farmers cannot eliminate insect breeding sites from pasture and woodland, Dr Bates says a meaningful impact around farm buildings is possible by minimising open dung heaps, slurry puddles, and old hay and straw stacks.
“For maximum control, do not wait until insects are bothering livestock as this allows breeding populations to become established and difficult to get on top of,” he advises.
In conjunction with good farmstead hygiene, Aurelie Moralis says residual pour-on pyrethroid treatments such as deltamethrin (e.g. Fly & Lice Spot OnTM) or alphacypermethrin (e.g. DysectTM Cattle Pour-On 15g/l and DysectTM Sheep Pour-On 12.5g/l) are licensed to control insects for up to eight weeks depending on species and population.
Research into the use of insecticides against the Culicoides midge species, known to be implicated in the transmission of several viruses including Bluetongue and Schmallenburg, found a deltamethrin-based pour on treatment to be an effective control method.
In the study, even hair clipped from the feet of cattle several weeks after standard treatment contained enough deltamethrin to kill midges. Aurelie urges cattle and sheep producers to discuss insect control options with their vet or qualified animal health adviser.
Farmers who wish to follow the progress of Parasite Watch can do so on Zoetis’ Twitter site: @sheep_farmers