Downy Mildew Continues To Plague Long Island Gardens

Cool nights and warm daytime conditions have brought downy mildew back into the spotlight on Long Island. The disease, which affects impatiens walleriana, is spread by air and by the splashing of spores due to rain and overhead watering.

“Recently a number of Long Islanders have come in with questions about their impatiens,” said Suzie Vezza, Hicks Nurseries’ green goods manager. “They mention that the leaves are yellowing and the undersides have developed a white, fuzzy-like color. These are classic symptoms of downy mildew.” Hicks has not sold Impatiens walleriana for several years.

Vezza said, “We continue to feel it is our responsibility to help stop the spread of downy mildew by not selling impatiens walleriana and instead offer alternative annual plants that will thrive in your garden.”

If you purchased impatiens and think your plants have been affected by downy mildew, here is what you need to know:

What is it?

Downy mildew is a devastating disease that can spread by air and by the ‘splashing’ of spores due to rain and overhead watering. It is prevalent across the country and can come from any number of places.

What are the symptoms?

Early symptoms include yellowing or stippling of the leaves, or a white, downy-like color on the underside of the leaves as well as stunting of growth. Advanced symptoms include a grayish, fuzzy substance on leaves and stems. Leaf and flower drop will eventually result in bare, leafless stems.

How did I get it?

Downy mildew is a water mold. The disease spreads most commonly when the foliage stays wet for extended periods of time and there are cool night temperatures and moist conditions. Therefore, areas of deep shade, beds that receive overhead watering and densely planted beds are more highly susceptible to downy mildew.

What do I do now?

Once the disease is identified, remove all of the plants and plant debris (leaves, flowers, etc.) from soil and containers. Spores can overwinter in the debris so the removal is imperative to help limit future spread. It is not recommended to plant impatiens in that location for several years. Chemical treatments are not recommended as most are ineffective.

What else can I plant?

There are many other flowering plants that thrive in shade and partial sun including landscape begonias, new guinea impatiens and Bounce impatiens to name a few.

Visit to learn more about downy mildew.

Karen Musgrave is a certified nursery and landscape professional (CNLP) at Hicks Nurseries in Westbury.

Karen Musgrave
Karen Musgrave, CNLP, is a marketing and education specialist at Hicks Nurseries and contributing writer to Long Island Weekly.

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