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updated: 6/11/2013 12:22 PM

Impatiens susceptible to downy mildew

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By Mary Boldan and Mary Moisand

Q. Every year my garden is exploding with impatiens. However, more and more I am reading about a disease that is attracting this popular annual. What can you tell me?

A. While many plants are susceptible to downy mildew, it usually does not kill the plant.

However, within the last few years, this has not been the case for impatiens (Impatiens walleriana). This popular annual has been hit with a disease called downy mildew of impatiens (Plasmopara obducens).

This disease affects all varieties of Impatiens (Impatiens walleriana). This includes common bedding impatiens, double impatiens and hybrid impatiens. One of the first signs of this disease is a white, velvety covering on the underside of the leafs.

Eventually, infected plants drop their flowers and leaves, resulting in bare, leafless stems that eventually collapses.

You should remove all of the diseased plants to avoid further infection in the garden. Do not put these plants in the compost pile.

However, it may be difficult to rid the planting area of this disease because there is some evidence that the pathogen can remain in the soil. Therefore, if you remember you impatiens dying prematurely last year, you may want to plant something different in that area, such as these shade-loving annuals:

• Begonias. These have a mounding habit and are shade and drought-tolerant.

• New Guinea impatiens.These impatiens are not susceptible to the downy mildew that infects impatiens walleriana.

• Coleus. This plant's best feature is its colored foliage.

• Provided by Mary Boldan and Mary Moisand, University of Illinois Extension Master Gardeners. Master Gardener Answer Desk, located at Friendship Park Conservatory, 395 Algonquin, Des Plaines, is open 9 a.m. to noon on Wednesdays. Call (847) 298-3502 or email

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