US (OH): Mildew making impatiens scarcer

Due to downy mildew, Baker’s Acres Greenhouse in Alexandria cut its impatiens plantings by 75 percent this year. Downy mildew is “greatly affecting the business,” said owner Chris Baker. “As far as bedding flats go, that’s the main crop because everybody uses them for shade.”

The disease was spotted early last year in Ohio after spreading from the East Coast. It prompted an alert from Ohio State University’s C. Wayne Ellett Plant and Pest Diagnostic Clinic after being identified in Delaware and two northeastern Ohio counties. It is carried by the wind, resists household fungicides and remains for months in the soil.

“It’s very difficult for customers to control,” said David Cuthbert, president of Cuthbert Greenhouse in Groveport. “It has the ability to decimate a customer’s impatiens.”

The first sign of the disease is white fuzz under the leaf, but by then, it’s probably too late to save the plants, growers say.

“Leaves will quickly defoliate,” said Brian Killilea, manager of deMonye’s Greenhouse in Columbus, which cut back impatiens production by two-thirds. “They will look like sticks. It rapidly goes from being beautiful to being wiped out.”

The disease affects only the walleriana species of impatiens and will not spread to other plants.

Downy mildew presents a dilemma for growers. They know impatiens is vulnerable to disease but also know that it’s the most popular annual flower in the nation. Homeowners will expect to find it in garden stores in May.

The problem is worsened because there’s no ideal substitute.

Other impatiens, such as the New Guinea species, are unaffected, but they are less shade-tolerant and more expensive than walleriana. Growers and sellers suggest gardeners try begonias, coleuses, lobelia and torenia instead.

If they stick with impatiens, they do so at their own risk.

DeMonye’s Greenhouse plans to hang a sign warning buyers of downy mildew, Killilea said.

“We used to have a big impatien sale before Mother’s Day,” he said. “We canceled that sale. We don’t want people disappointed, and when we do sell them, we want them to know: Buyer beware.”

Nancy Taylor, director of Ohio State’s plant and pest diagnostic clinic, also urged gardeners to use caution.

“I would suggest that they be aware that the disease could develop later in the summer,” she said. “We don’t know yet whether this disease will arise again but they might need to think about. If they do see this disease, it would be very difficult for to stop it.”

Source: dispatch.com