Sheep are constantly under attack from a host of creepy-crawlies. During the winter there are biting lice, keds and sheep scab mites. They are extremely irritating and cause sheep to rub themselves against fence posts or to constantly nibble their itchy fleeces.

Those little pests are followed in the spring by ticks that suck their blood. That’s not as painful as it sounds, but it spreads serious diseases such as tick-borne fever, border disease or louping-ill.

During the late spring and summer months there are head flies that attack the skin at the base of the horns, creating nasty sores.

Worst pests of all, particularly at this time of year, are greenbottles or the blow fly Lucilia sericata. Their cousins, bluebottles, lay eggs on dead animals that hatch into larvae or maggots, but blowflies lay their eggs on live sheep and their maggots eat living flesh and can literally eat a sheep alive.

Blowflies can be a big problem at this time of year, particularly when it is humid, as that’s when they are most likely to lay their eggs on soiled parts of the fleece particularly around the tails and backsides.

In the autumn, when bracken on the hill died back, I often found skeletons of sheep that had died a painful death. Sheep logic is to try and hide from the pain of the maggots, sometimes making it impossible to find them as they cower beneath a waist-high canopy of bracken. Tragically that seals their fate, although those that can be found are easily cured. It’s simply a matter of clipping away wool from the infected area, scraping off the maggots with the shears and then soaking the surrounding area of the fleece with a solution of insecticide, called sheep dip, to prevent any more eggs being laid or hatched out.

Mind you, maggots in a hoof that had been infected with footrot can be a blessing in disguise providing the sheep is caught in time and treated. The maggots nibble away the infected part of the hoof allowing it to heal. The same idea is used in hospitals in human medicine when doctors apply maggots to infected wounds to clean them up.

Blowfly strike is a major problem for the UK sheep industry that costs around £2.2m annually and affects over 80 per cent of farms.

The prevention is to apply insecticides to the sheep in a concentrated form either as an injection or in very small quantities onto the backs of the sheep, or by immersing, or plunge-dipping them in sheep dip for at least a minute.

Plunge-dipping has gone out of fashion to some extent, but for all its problems, I still believe it to be the best method. A large tank or dipper is filled with 1,000 or 1,500 litres of water and then has the dip or insecticide mixed in. Invariably the insecticides have no smell, but manufacturers add other strong-smelling ingredients to make farmers think their dip is a powerful concoction.

Unfortunately, plunge-dips are based on organo-phosphates developed from nerve gases used in trench warfare. They are very effective, but have caused health problems with farmers in the past. As a result, operators now need to have a certificate of competence and wear waterproof safety clothing comprising wellington boots, waterproof trousers and bib or apron, face mask and heavy duty rubber gauntlets. All that protective gear can make for a hot, sweaty days work.

Dipping is hard work and not for the inexperienced. Sheep have long memories and hate being immersed in a cold bath full of smelly chemicals. You know and I know it’s good for them, but I’ve never yet managed to convince a sheep of that.

In my experience they have two reactions. One is to dig their toes in and refuse to budge until pushed or hauled to the edge of the dipper and dropped in. Or they may take a runner at it and dry to clear it before belly-flopping into it about two thirds of the way along and drenching everyone in the vicinity.

Like most jobs there’s a knack to dipping sheep. The trick is to stand in such a way as to encouraged the sheep to move between yourself and the dipper. Just as it passes the dipper, you catch it under the jaw with one hand, grip the loose skin between its hindquarter and belly with the other hand and nudge it in with your knee.

It looks effortless when done properly, but you would be amazed at how easy it is to slip and fall into that dipper.