Impatiens Downy Mildew
- Attacks impatiens walleriana, which are traditional impatiens.
- Symptoms are yellow foliage, leaf loss, stunted plants and reduced flowering.
- The most distinct sign, which can be difficult to see, is gray downy fuzz on the underside of the leaves.
- It is spread by aerial spores from neighboring impatiens plants. They may live in the ground for up to 10 years.
- High humidity, excess rain and prolonged irrigation contribute to the spread.
- The infected plants should be placed in a sealed plastic bag and thrown in the garbage. Do not compost.
- Remove all plant debris including leaves, stems and roots.
Source: Siebenthaler’s Garden Center
Rethink the popular Mother’s Day gift of impatiens.
The traditional variety of the annual shade plant is being ravaged by a downy mildew that’s shown up from the east coast to the Midwest and Ontario.
As it spreads, the mildew leaves its trademark grey downy fuzz on the underside of leaves. Because it’s so early in the season, an exact fix on where it could show up this year in Ohio isn’t available yet.
But it is the number one bedding plant in the country, so garden stores are preparing for outbreaks.
“This is a market changer, this particular disease,” said Pam Bennett, horticulture educator for Ohio State University’s extension office in Clark County. “We really don’t know where it will show up.”
Some retail outlets in Michigan have simply stopped carrying the plant. Detroit-area stores are keeping them off the shelves. The disease began showing up in U.S. production greenhouses in 2004. In 2011, it began showing up in large regional outbreaks around the country.
Local gardening outlets say that when the disease presents itself, gardeners should not replace the plants with another set of impatiens walleriana, the variety affected, but instead use other shade plants.
Once plants have been diagnosed, the disease can live in the soil for 10 years. Ohio’s impatiens suppliers have told retail outlets that they’ve cut their impatiens production in half and bumped up their production of begonias.
The impatiens market depends on the age of the neighborhood. Older neighborhoods with mature trees and ample shade are big impatiens purchasers. The impatiens market isn’t so hot in newly developed areas where the trees are new and shade is rare.
Siebenthaler’s Garden Center, 6000 Far Hills Ave., is on the front lines. Melody Johnston, greenhouse supervisor, said that this year many customers are avoiding impatiens. She’s recommending begonias, coleus and the New Guinea impatiens variety, which is not affected by the mildew.
The mildew isn’t hitting Siebenthaler’s bottom line, Johnston said. Gardeners are switching.
“People are just buying something else,” she said. “We anticipated the problem. We have lots of Coleus on hand and sell a lot of begonias.”
It’s much the same story at North Dayton Garden Center, 1309 Brandt Pike, Dayton, said general manager Rick Kossoudji. North Dayton is still growing the plants and is managing to hold off the mildew with fungicide spray, but also recommends using other plants.
“Many other plants will grow in the shade and thrive,” Kossoudji said.
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