Disease threatens garden impatiens
Surprising scientists and horticulturalists, once-mild downy mildew disease has struck the popular blooms in 33 states

By Susan Milius

A puzzling plant disease may dethrone one of the most popular and reliable flowerbed plants in North America, the garden impatiens.

A relatively benign condition known as impatiens downy mildew has recently turned ugly, for reasons under debate. For decades, U.S. gardeners rarely noticed downy mildew on their impatiens. But in the last two years, the disease has ravaged flower beds in some of the more humid parts of the country. After rain or fog followed by balmy nights, the disease can turn a lush flower border into a straggle of bare stalks that eventually collapse and die.

In recent years, aggressive impatiens downy mildew has flared up during disease-friendly weather in parts of Europe, South Africa and Australia. But the United States hadn’t seen more than a few scattered reports until widespread outbreaks began in 2011. By the end of 2012, pathologists had confirmed the disease in 33 states and Washington, D.C.

The disease is unlikely to eradicate the plants, but in some areas of the country, the risk can change a gardener’s mind about what to plant. Impatiens downy mildew “thrives in our coastal climate,” says plant pathologist Nancy Gregory of the University of Delaware cooperative extension program in Newark. In advice that would have been shocking a decade ago, she suggests gardeners skip impatiens unless willing to cope with the risk of an unsightly die-off.

More: http://www.sciencenews.org/view/generic/id/349064/description/Disease_threatens_garden_impatiens