Tips on Impatiens Downy Mildew
You may have heard scare stories about the familiar shade impatiens (Impatiens walleriana). Impatiens have been banned! You can’t buy them any more! The fact of the matter is this:
Impatiens are susceptible to a disease called Impatiens Downy Mildew (IDM). The disease is believed to have arrived in the Erie area around mid-August 2012. IDM is characterized by stunting and by downy white lesions on the undersides of the leaves. Eventually, leaves wilt and fall off, leaving only bare stems. If you experienced this in your garden in 2012, you may have simply assumed it was “that time of year”. In many areas, the disease has become so severe that growers have simply discontinued growing impatiens altogether.
The management here at Stan’s has discussed this reality at length. Our response is to commit ourselves to offering a disease free crop; offering alternatives for those who don’t want to take the chance, and providing the information necessary for you our customer to make an informed decision. Here’s what you need to know:
IDM spores are carried short distances by splashing water and longer distances by wind and air currents, They are not killed by Erie winters, so plants placed in a flower bed infected in the past will almost certainly be infected this year. Spores require 4 hours or more of wet foliage to germinate. To deter spore germination…
DON’T PLANT TOO EARLY! Frequent rains and cool temperatures create the ideal environment for IDM to take hold. Wait until early June to plant, when weather has warmed and rains are less frequent.
DON”T WATER EVERY DAY! Even some experienced gardeners are under the misconception that gardens need daily watering. At best this is a waste of time; for IDM watering every day creates risk for infection every day.
DON'T WATER OVERHEAD! This admittedly is easier said than done. Still, gardens can be watered with a soaker hose, containers by directing the hose beneath the foliage. If you have to water overhead, do it early enough so that the foliage can dry as quickly as possible.
What about chemical controls? Some fungicides containing chlorothalonil (Daconil, Fungonil), copper compounds or neem oil are labeled for downy mildew control and may be effective. These need to be rotated bwith one another and applied as a preventive before symptoms appear; once the disease is apparent, it’s too late to control it.
If you decide impatiens aren’t worth the trouble, here are some possible alternatives:
Wax Begonia Inexpensive Limited color range (partial sun) Readily available (red, pink, white)
Tuberous (NonstopTM) Good color range More expensive
Vinca (catharanthus) Good color range Prefers heat & sun
New Guinea Impatiens Excellent color range Tend to cost more (including Divine series)
SunPatiensTM Look like NGI More expensive