The much despised cane toad, one of Australia's most destructive pests, may be about to meet its match - a 'daughterless gene' that would ensure female toads could produce only male tadpoles. The gene is being developed in Queensland, the state that was first overrun by Bufo marinus after it was introduced from Hawaii in the 1930s in a failed attempt to control sugar cane beetles. If successfully engineered, it would ensure that cane toads bred themselves out of existence, with millions of lonely males eventually dwindling to extinction. Impeding the toads' breeding cycle is particularly effective in combating the species' inexorable expansion because a female toad can lay up to 30,000 eggs at a time. Developmental biologist Peter Koopman, of Queensland University, unveiled the gene project at a national cane toad conference in Brisbane, saying the gene was much safer than other strategies. 'There are no poisons, toxins or viruses being released into the environment. The possibility of this spreading to other species is zero. We're looking at letting them loose in two to five years' time,' Professor Koopman said. Once released into the wild, scientists hope that the genetically altered toads would mate with as many ordinary toads as possible. Cane toads have proved remarkably resilient, spreading south into New South Wales and west into the Northern Territory, where they have invaded World Heritage-listed Kakadu national park. Toxic glands in their skin are lethal to indigenous animals that eat them. Even their eggs and tadpoles are poisonous.