11 February 2000

Turn a blind eye to bunnies at

own risk

IGNORING rabbit control this winter is as risky as forgetting fungicide or herbicide applications, warns one expert.

"Each rabbit eats about 120g of dry matter every day. So even a small population consumes a huge number of cereal shoots during the winter," says Roger Trout of Rabbit-Wise consultancy.

Grain loss, uneven growth, delayed ripening, more weeds and difficulty timing sprays to growth stages can all result. Total losses are much greater than the obvious grazed area on field edges, says Mr Trout.

At five rabbits/ha (2/acre) about 5% of winter wheat yield is lost. In a square 7ha (17 acre) field, that equates to 2.5t or £200 worth of grain. Yet growers may only see 2-3 rabbits on each side of the field.

"Only 25-30% of a rabbit population is ever seen at any one time. You dont have to see many to know you have a potential problem," he warns. "Doing nothing is not an option."

On most farms rabbit management is poorly planned, relying on some shooting and the odd ferret. But growers have over 30 methods of managing rabbit damage available, including changing crop. While not all are appropriate everywhere, a farm-specific management campaign should be planned, he says.

Mr Trout, who is based in Farnham, Surrey, adds that fencing using the new longer life green rabbit netting of British Standard mesh works extremely well if erected and maintained correctly and can pay for itself in two years.

However, where a severe rabbit infestation suddenly becomes apparent after crop emergence, immediate fumigation of nearby burrows, killing up to 90% of rabbits, is often justifiable.

Two forms of fumigation are legal. Cyanide-based powder has a very rapid knockdown of all vertebrates, including humans. Spooning cyanide powder into holes or filling hand or motorised pumps is a potentially dangerous. Tablet products producing phosphine, especially brands coated to delay the release of the gas, are considered much safer, he says.

MAFF trials indicate that Cymag (sodium cyanide) and Phostoxin (aluminium phosphide) treatments result in similar rabbit population reductions but that more burrows/hr can be treated using Phostoxin. Whichever is used, operators should de trained in fumigant use, including safety, handling, transport and storage, he stresses.

"Two people, wearing coveralls, boots and impervious gloves, should work together to treat all holes and immediately backfill. It is a winter job for dry days."

Fumigating only one side of a hedge, bank or railway line is ineffective. All holes in a warren must be fumigated to do a good job, and reopened holes must be treated again 2-5 days later.

Replacing grazed crop with a setaside strip may seem expedient but rabbits will still prefer the cereal and eat even more next year and be more expensive to control, he warns.

"Some may argue rabbit control is so expensive that it is easier to let a hectare go than pay for control. But annual spraying cost/ha is much greater than a well planned rabbit management strategy."

EFFECTIVE BUNNY CONTROL

&#8226 Combine methods.

&#8226 Seek advice on management strategy.

&#8226 Be safe with fumigants.

&#8226 Controls must be thorough.

&#8226 Work with neighbours, owners and landlords.

RAMPANT RABBITS

&#8226 UK Rabbit numbers rising.

&#8226 £40m/yr of cereals lost.

&#8226 1% crop loss/rabbit/ha.

&#8226 Only 20-30% of population seen at any one time.

&#8226 15-25 young/doe/year.

&#8226 Myxomatosis and rabbit haemorrhagic disease very variable impact.

RAMPANTRABBITS

&#8226 Rabbit numbers rising in UK.

&#8226 £40m/yr of cereals lost.

&#8226 1% crop loss/rabbit/ha.

&#8226 Only 20-30% of population seen at any one time.

&#8226 15-25 young/doe/year.

&#8226 Myxomatosis and rabbit haemorrhagic disease very variable impact.