A Mold Devastates Impatiens - NYTimes.com Béatrice de Géa for The New York Times Dumpling planters overflowing with impatiens, a breed of flower beloved by the home gardener. A mysterious strain of downy mildew has been killing one of the home gardener's favorite annual flowers, Impatiens walleriana, up and down the East and West Coasts, in the Midwest, Texas and Ontario. "We saw it here in 2011 in the fall, and it was really dramatic," said Margery Daughtrey, a plant pathologist at the Cornell University extension center in Riverhead, N.Y. "Gorgeous plants, flowering two feet tall, and then the flowers start disappearing and leaves drop and stems fall over and then the stems disappear." Since then, it has only worsened. Lois Carswell, the co-chair of the Brooklyn Botanic Garden plant sale, which has been held in early spring for the last 60 years, said it has always done a brisk business in impatiens. But last year, the garden's growers, which supply more than 20,000 plants for the sale, were seeing so many diseased plants in greenhouses and gardens that they decided not to offer Impatiens walleriana or any of its hybrids at this year's sale later this month. Impatiens is an overused plant I love to hate, so I am shedding crocodile tears. All those red-and-white, pink-and-purple flowers planted like petticoats under the trees - as if trees needed skirts. Maybe nature is doing us a favor by forcing those addicted to the plant to find an alternative. Still, annual bedding plants are a $2 billion industry in the United States, and the colorful Impatiens walleriana has long been one of the best sellers. For years, it was sold by the millions by growers that buy seed from Ball Horticultural Company, Syngenta Seeds and others. And as recently as 2009, it reaped $174 million wholesale annually, according to the Agriculture Department. But now, the endangered pinup girl is having a rocky time in the marketplace. Some growers are still pumping it out, but many have stopped cold. Walter Gravagna, an owner of Van de Wetering Greenhouses in Jamesport, N.Y., which produces 300 million plugs, or seedlings, of annuals a year, said his production is down by 20 percent. "We supply wholesalers from Michigan to Maryland and up to Maine, and 40 percent of that used to be impatiens," he said. But "with downy mildew really hitting the East Coast, from the mid-Atlantic to Maine, that supply has gone down considerably." Home Depot is still selling the flats, but is training its staff to spot the disease and is educating customers about the risk involved if they insist on the one and only, said Stephen Holmes, a spokesman at the company's headquarters in Atlanta. And "we'll have less supply east of the Mississippi," he said, where the flow of plants has been reduced by 25 to 40 percent. The disease is a mold (Plasmopara obducens) that thrives in cool, damp conditions and first appears as a white, downy coating of spores on the undersides of leaves, so it's easy to miss. By the time gardeners notice the flowers drooping, it's too late to do anything. So far, it has swept through 33 states and the District of Columbia, and has been confirmed in Ontario, with possible outbreaks in British Columbia and Quebec. It showed up in England in 2003, and spread so quickly through greenhouses and gardens that Britain's Department for the Environment, Food and Rural Affairs placed a quarantine on the movement of diseased plants, Ms. Daughtrey said, "banning their sale, requiring disposal, that kind of thing." She continued: "In 2004, we saw a little bit of it in New York in greenhouses, and Tennessee and California. But it didn't amount to much. Growers destroyed the infected plant material, stepped up their fungicide regimens, and the disease disappeared. Now and then, a sample would find its way into her lab at the Long Island Horticultural Research and Extension Center, but it didn't seem to be cause for concern, because the disease only attacked Impatiens walleriana, and although it had been in North America since 1800, it hadn't spread.