Impatiens Downy Mildew – Identification and Substitutes
Q: I have been told by a local garden center that garden impatiens, except the New Guineas, have a disease this year and should not be planted. Is this the case or maybe an exaggeration?
A: It is true that garden impatiens have been hit hard by downy mildew in some parts of the U. S. in the last couple of years. Large growers have had to practice scrupulous inspections to be sure they don’t ship infected plants to garden centers. Downy mildew causes the plant’s leaves to yellow. As the disease progress, both leaves and flowers drop. White spores form on the underside of leaves and thus may go undetected until it is too late to save the plants. Once the disease infects impatiens in a flower bed, the soil remains infected for several years.
I’d plant them sparingly and see what happens. Mildew tends to be worse in locations where leaves stay wet for extended periods of time, in very dense beds and in beds receiving overhead sprinkler irrigation, because the foliage does not dry quickly.
Mark Whittier, Pike Nurseries buyer, reminds us that:
- IDM is not carried in seed.
- This is not a new disease. IDM has been in the US since the early 2000’s, so reputable growers have been aware and consistently taken preventative steps since that time.
- All of Pike’s growers use rigorous practices to prevent the innoculum, and constantly inspect for indicators.
- Anyone who purchases Impatiens should be wary of suppliers who are not aware of the prevention protocols of their growers.