Australian farmers are being urged by authorities to use poison gas and even ammonium nitrate explosive to blow up rabbits, as biological controls fail, The Adelaide Advertiser reported in its Thursday edition.A warning issued to farmers by the South Australian Environment Department urges them to "overcome the rabbit's tremendous breeding potential" by traditional means such as bulldozers, poison baits, fumigation, dogs and even explosives. "Explosives are an alternative for follow up control . . . accreditation and training is mandatory," the information bulletin issued by the Arid Lands Natural Resources Management Board (ALNRMB) states.