Impatiens Disease - Downy Mildew


Impatiens have been one of the most popular landscape plants in the garden for years, however Downy Mildew is changing all of that for the once mighty king of annuals.

In Michigan, most experts thought the disease would never travel this far North. However, late last summer Downy Mildew sporadically showed up all over Southeastern Michigan and once beautiful Impatiens beds became an eyesore in the landscape. To avoid a season of frustration, disappointment and failure, we recommend not buying and planting impatiens in 2013.

We know that you shop with us because we have the quality plants and selection you love but also because we give you the knowledge and information you need. And your success is our number one priority. With that in mind, we have made the difficult decision to stop growing and selling regular and double Impatiens for this year. Other reputable local garden centers have also come to the same conclusion. They include Bordine’s, Ray Wiegand’s Nursery, Plymouth Nursery and Farmer John’s. There is some good news though, New Guinea Impatiens and SunPatiens are not affected by the disease and both offer similar garden performance. Other alternatives include Begonias, Coleus and Vinca. So embrace the change and mix it up a little this year.

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Quick Facts

What is Impatiens Downy Mildew?

Downy Mildew is fungal blight very similar in appearance to Powdery Mildew, a common fungus on garden phlox and lilac bushes. Powdery Mildew is treatable but unfortunately with Downy Mildew there is no cure and the plant will eventually weaken and die.

What are the symptoms of Impatiens Downy Mildew?

Impatiens exhibiting symptoms of downy mildew may appear different from landscape to landscape depending on how advanced the disease is. Early symptoms include leaves with light-green yellowing or stippling. The leaves may also curl downward; have gray markings on the upper surface or white fungal growth on the undersides.

Advanced symptoms include stunted plant and leaf growth, bare plants as the result of leaf and flower drop and softened, weak stems.

How does the disease spread?

Downy mildew is spread by spores on the undersides of infected plant leaves. Because the spores easily detach from the plant, they can be spread by wind or water splash. In the landscape, spores can travel hundreds of miles via wind currents, and plants not yet showing symptoms may unintentionally infect those around them. It spreads most easily in moist conditions. The symptoms for a homeowner can show up in just a few weeks, even if they purchased clean plants that were disease free. The disease is also capable of surviving the winter in the soil and on plant debris. Therefore, reinfestation is almost certain.

What plants are susceptible to this disease?

Downy mildew affects all types of standard impatiens (Impatiens walleriana), including doubles, minis and interspecific hybrids such as Fusion. It is not a problem on New Guinea impatiens (I. hawkeri) or any of the other popular annual choices.

Is there anything I can do to prevent my plants from getting Impatiens Downy Mildew?

There is no product on the market today that will cure this disease. There is however preventive fungicides that will help control Downy Mildew but only when on an aggressive schedule. Environmentally, this is not a realistic approach since most chemicals need to be applied every 7 days by a certified applicator.

What if I find Impatiens at another retailer, can I plant them and will they survive?

Even if the plants are disease free at the time of purchase, it is just a matter of time before the wind will spread the disease onto those plants. A trial in Florida, planted in early January 2013, had impatiens flowering for 4 weeks before the disease took over. In February, the disease was a confirmed present in Georgia and South Carolina. It only takes a few of these spores moved by the latest weather event to spread the problem.

What can I plant in my yard instead of Impatiens?

There are many shade-tolerant annuals that are resistant to IDM including New Guinea Impatiens, SunPatiens, Begonia, Caladium and Coleus. Sun tolerant annuals that make great alternatives include Vinca Rosea, Marigolds, Salvia and Petunias.

Impatiens Alternatives