Just as there is currently an abundance of "cute" Easter Bunnies on display in many shop windows, so too have real ones returned to my garden. They are, from time to time a big problem, because instead of confining themselves to grazing the lawns, they nibble many of the plants in the herbaceous borders. They also have an uncanny knack of selecting and destroying the most expensive shrubs.

It's their method of grazing rather than the amount they eat that causes so much damage in agriculture. They nibble the grass so closely that it doesn't grow again and is soon replaced with mosses that typify a rabbit-infested pasture.

It's reckoned that ten rabbits eat as much grass as one ewe. So a farm with a modest infestation of several thousand rabbits could have kept another couple of hundred ewes. Once again it's not just the grass they eat that is the problem. Rabbits graze out the best grasses, encouraging poorer types that cattle and sheep don't like, and their droppings and urine contaminate even more pasture than they consume.

Not only do they eat crops, but they also stunt the growth of large areas leading to lower quality, unevenly ripened grain.

Young trees become deformed after the buds are nibbled, and are often killed in frosty weather when rabbits strip the bark. That is why we have to protect newly-planted hedges and woods with expensive rabbit-proof netting that must be dug into the ground to prevent them burrowing underneath.

Some arable farmers sow a strip of phacelia round the edge of their fields to keep rabbits out of the main crop. Bobtails don't like the sticky leaves of this plant and hate the taste - they may nibble it once out of curiosity, but never again.

Like rats and mice, rabbits can soon multiply into large populations. Their main breeding season is from January to July, but there are no hard and fast rules as some rabbits can breed all the year round. They are also extremely fertile - a doe can breed in her first year before she's fully grown and mates again within a few hours of giving birth. That means that each litter, of about six or eight young, is separated only by the length of pregnancy, which is about a month.

Before myxomatosis appeared in Scotland in the 1950s, rabbits were the farming industry's number one enemy. Some parts of the country became so overrun with them that it became impossible to farm and the land was literally abandoned.

When myxomatosis first struck in the south of Scotland in 1955 there were dead and dying rabbits everywhere and millions perished. Indeed it seemed as if rabbits had been wiped out.

The disease is spread by fleas that easily jump from rabbit to rabbit in a crowded warren. It its final stages, the infected rabbit's eyes swell up and they become blind.

It's amazing how living organisms can adapt and evolve to cope with challenges, and rabbits are no different. Over the years their numbers recovered as they became resistant to the disease.

Just when farmers were beginning to despair, rabbit haemorrhagic disease (RHD), also known as viral haemorrhagic disease (VHD) appeared. It's a very serious infectious disease which first emerged in China during the 1980s that within a few years was seen virtually worldwide, and is now an endemic disease in wild rabbits in the UK. It has killed more than 60 million rabbits in Italy alone and has spread to over 40 countries.

Chinese myxomatosis, as it has become known, is extremely sudden in onset in many cases, with the only sign seen in an infected rabbit is that it is found dead.

In addition to rabbits becoming resistant to myxomatosis, the most severe form of anticoagulant resistance identified in rats has spread right across the whole of central southern England, affecting the most widely used poison baits, according to a recent report.

The resistance affects the efficacy of first generation and some second generation rodenticides used to target the Norway rat, which is the only problematic rat species found on farms in the UK.

The main rodenticides used in the UK are chronic anticoagulants, which cause death by haemorrhage.

First generation anticoagulants contain the active ingredients warfarin and coumatetralyl, while second generation anticoagulants use a broader range of compounds.

The report also found the UK leads the world with the highest number of different genes for resistance in rats.

The ability of all organisms to develop resistance to disease and chemical control is a real challenge for farmers.