The Milwaukee Journal Sentinel had this article on emerald ash borer: http://www.jsonline.com/story/index.aspx?id=617306 I had heard earlier this week about introducing wasps to fight the ash borer, which causes me concern. I just saw a documentary with David Attenborough's soothing voice telling me how introducing the poisonous cane toad to Australia to battle a beetle menace has backfired -- the toads didn't eat the beetles but overran the country. (info: http://www.fdrproject.org/pages/toads.htm)
The Glory days of introducing one scourge to fix another are largely over in North America and definitely over in Australia and New Zealand. One of those 'We won't do THAT again!' That said, natural control methods are being introduced into North America to control introduced pests but only after extensive testing to ensure that the control is host specific and collateral damage is minimized. Biologists have learned Cane Toad lessons well. After one has hiked in the woods of the Northeast, a person realizes how important it is to find some sort of biological control of the Emerald Ash Borer, as the Ash is one of the dominant forest trees species.
Unlike other Hawaiian islands Kauai was spared infestation with mongooses because someone saw the crates of them on the dock and kicked them into the ocean. These were deliberately introduced to control rats in sugar cane fields but instead went on to become pests themselves.
Present-day biological control agents are selected and tested with great care. In Florida, it can take well over a decade from identification of a problem to release of even a single agent. Melaleuca control is coming along well, prospects look good for Schinus terebinthifolius, and an agent's been released to control a weevil that eats bromeliads.
^ what dave said. control agents/organisms are still invaluable, and they're checked out six ways from sunday. the phorid fly for fire ant control is my favorite example.
