THE NEW YORK TIMES, SUNDAY, SEPTEMBER 3,2006 OPINION   EDITORIALS Hope Against a Scourge      It's the best news in years for the people of Shelter and Fire Islands, who have been suffering from an infectious plague that they have been unable to fight effectively, except by obsessively combing their bodies for deer ticks and taking endless rounds of antibiotics. The New York State Department of Environmental Conservation has changed its mind and decided to allow Shelter Island and parts of Fire Island to install four-poster deer-feeding stations, which coat the h,eads and necks of deer with a pesticide that kills the ticks that carry Lyme disease.      The problem with Lyme disease and other tickborne afflictions is that methods to prevent them tend to be indirect, time consuming, prohibitively expensive or distasteful. Ticks live on deer, and subduing deer is ferociously difficult. Deer-infested communities have spent years trying any number of 'approaches to keep them at bay, like recreational hunting and birth control, with dubious results. One ,strategy is to slaughter the deer, but many people hate that, and even if you turned every last suburban Bambi into steaks and sausage, you would not necessarily subdue the parasitic araclfnid that is at the root of this growing problem.     The four-poster device takes a different, lethally direct approach that offers some hope, at least in controlled circumstances. It was developed by a federal agriculture official and works by luring deer to a bin baited with corn kernels and rigged with rollers soaked with permethrin, a tick-killing pesticide. The deer eats and rubs against the rollers, and ticks die by the thousands. One station can treat all the . deer in about 100 acres.      New York bans four-poster devices because the Department of Environmental Conservation is not convinced that they are safe or effective; the department also opposes feeding wild deer. Feeding deer makes them congregate, which increases the risk of spreading chronic wasting disease.     We agree that it is generally a terrible idea to feed deer - or any wild creatures with a tendency to multiply uncontrollably. This is not only out of pity for chronically wasting deer, but because of the dangers that dependent deer pose to people, who drive into them on highways, and the damage that swelling herds of emboldened nibblers do to gardens, parks and woods.     But if feeding deer is a bad idea in general, it could be a very good one in isolated places like Shelter Island and Fire Island, where the herds are separated from the rest of the state deer population and where Lyme disease and other tick-borne illnesses constitute a genuine public health emergency.     A controlled experiment that directs a focused assault on ticks makes perfect sense, and is a welldeserved victory for the island residents who relentlessly pressured town and village officials to drop their resistance to four-poster devices. Credit should also go to Gov. George Pataki, who issued the order clearing the way for the four-poster study last month after being urged to do so in a letter from former Gov. Hugh Carey, a Shelter Islander who knows the problem well.     The next step is to pay up. New York State, Suffolk County and town and village officials on Shelter and Fire Islands should come up with funds to augment the private contributions that are even now being raised to finance the four-poster study. The tick scourge has gone on too long, and this should be the beginning of the end.