Map showing the states infected with Downy Mildew.
Much Ado about Impatiens!
2013 Downy Mildew Update
Downy mildew is still with us, overwintering in our soils, and that’s a problem for everyone who loves Impatiens walleriana, the favorite shade garden annual. Last year it spread across the northern Seaboard and through the Southeast and to Texas. Reports of the disease were also documented in California, Oregon and Washington.
The disease is spread two ways: (1) by plants that are already infected with the pathogen and purchased by consumers and landscapers who plant them in their gardens; and (2) from spores spread by rain or irrigation (which splashes spores onto neighboring soils), and by wind currents which carry the spores to new territories.
Plants infected with the disease become defoliated after being installed in the landscape, leaving nothing but withered green stalks devoid of foliage and flowers. This is known as the “green stick syndrome.” (Earlier in the growing season, infected plants will be stunted, remain small, and fail to thrive.)
Infected Impatiens and all their leaves and flowers should be removed immediately and disposed of - do not compost the diseased plants, and do not replant Impatiens walleriana in the same bed, because spores will overwinter and reinfect plants again the following season.
Spores remain in the soil for years after the disease has been introduced. The pathogens, known as “oospores,” have over-wintered in Delaware and New York (Zone 5), indicating that the spores are resistant to very cold temperatures. No one has yet determined at what winter temperature the spores may die. Because the spores over-winter in the soil, they germinate again in the spring, which begins the process of infection all over again, if Impatiens walleriana are re-planted in the same location.
Once the soil has become infected with downy mildew, do not replant Impatiens walleriana in the same flower beds. It is not yet known how long the disease will remain in the soil, but it is assumed it could be many years based upon the studies at Ball Horticultural Co.
The above information was obtained from the 2013 report by Dr. Colleen Warfield and Nancy Rechcigl at ANLA, and at Ball Publishing which includes a Risk Assessment Chart for Impatiens walleriana, HERE.
So what can you plant in the shade this year? Click HERE for some ideas.
A welder at a boat-and-sub-building yard adjusts her goggles before resuming work, October, 1943. By 1945, women comprised well over a third of the civilian labor force (in 1940, it was closer to a quarter) and millions of those jobs were filled in factories: building bombers, manufacturing munitions, welding, drilling and riveting for the war effort.
See more photos here.
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