The June and early July rains look set to fuel a fly explosion in many regions of the country. With conditions so wet and warm, fly breeding grounds have been plentiful and farmers need to prepare for an onslaught on their livestock.

Richard Wall from the University of Bristol

“Many of the flies that plague cattle and sheep have aquatic larvae and warm, wet weather only helps increase their breeding success,” says applied biologist Professor Richard Wall from the University of Bristol.

“Moisture allows them to build greater fly numbers either later this summer or next season depending on the species. And the incidence of blowfly strike usually soars when summer weather is warm and wet,” he warns.

Horse flies, black flies, common cleggs and midges all lay their eggs in and around water. Horse flies lay eggs in damp or wet sites and when the adults emerge they are very aggressive blood feeders. They deliver a painful bite that can easily disrupt livestock feeding behaviour. Black flies prefer fast-running streams and rivers but are also voracious blood feeders, sometimes causing allergic reactions in livestock.

Common cleggs and midges (Culicoides spp) also feed on blood. Cleggs are often found on the legs of cattle, while midges bite and suck blood early in the morning or late afternoon.

“The rains many areas of the UK experienced last month will undoubtedly increase fly populations, particularly if it stays warm. Livestock farmers need to be vigilant for the remainder of the summer,” Professor Wall advises.

Schering-Plough Animal Health livestock veterinary adviser Paul Williams MRCVS says that because of the recent weather farmers need to seriously consider re-treating cattle now with a proven insecticide.

“With the extreme rainfall we have had recently – and the conditions now being so ripe for fly breeding – farmers should consider re-applying deltamethrin insecticides such as Coopers Spot On.

“Coopers Spot On is rainfast, meaning it won’t wash off cattle at pasture so easily. Its oil-based carrier also helps the deltamethrin spread quickly over the whole body. Studies show flies being killed on the head, belly, legs and rump within two hours of a single 10ml spot being applied to the back of the animal,” he says.

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