News from the State Horticulture Program Thinking
As you gear up to order plants for next spring, it’s important to remain up to date on new pests that could potentially arrive on the nursery stock you purchase. This knowledge can help you decide where to order your plants from, what plants to pay particular attention to checking over when they arrive, and what symptoms to look for. Whether you’re a landscaper, nursery, or greenhouse owner or worker, the following are a few pests to become familiar with.
Ahead:
By Ann Gibbs, State Horticulturist and Carole Neil, Assistant State Horticulturist
Impatiens downy mildew
Impatiens downy mildew has become problematic particularly in eastern states and many growers are looking at promoting other types of shade loving annuals. Here is some information on this new pest excerpted from the NJ Department of Agriculture website. Impatiens downy mildew is a destructive foliar disease of
Impatiens walleriana (garden impatiens), I. balsamina (balsam impatiens, garden balsam, or rose balsam), I. pallida, and I. capensis (native wild impatiens known as jewelweed). It does not threaten other flower or vegetable crops. Fortunately, Impatiens x New Guinea Hybrids (New Guinea impatiens) is not affected. While there have been sporadic reports of this disease in production
greenhouses in the United States since 2004, widespread regional outbreaks of impatiens downy mildew were observed for the first time in North American landscapes in 2011. Tere was one report of impatiens downy mildew out of southern Maine this August. Downy mildew symptoms on infected plants begin with leaf stippling, downward curling of leaves and leaf yellowing. A white, downy-like growth may be present on the underside of yellow leaves, but can also be found on the underside of green leaves. As the disease progresses leaf drop occurs resulting in bare, leafless stems.
Left Impatiens plant infected with impatiens downy mildew - photo by Don Ferrin Published May 21, 2012. Right: Impatiens downy mildew symptoms Courtesy of The Ohio State University Department of Plant Pathology
10 Fall2012
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