First, a recap of what Impatiens downy mildew (the fungus-like Plasmopara obducens) looks like: Did your impatiens seem to collapse in 2012? Impatiens walleriana, the ones we most often plant. These are classic symptoms of downy mildew, a water mold that affects impatiens walleriana and has no known cure. Since this pathogen is more prevalent in warmer climates, if you live in a northern gardening zone, avoid buying plants from nurseries that ship their plant stock in from southern greenhouses. Where does impatiens downy mildew come from? Keep them in a holding area and watch them for symptom development. Horticulturist Jessica Walliser is an award-winning radio host on KDKA Radio’s “The Organic Gardeners” in Pittsburgh. Downy mildew is caused by a pathogen called Plasmopara obducens, a fungus like organism that is actually a member of the water molds family, Oomycota. Sanitation is the best management strategy for this disease. DO NOT use fungicides on plants that are showing symptoms as such treatments will not be effective. Â. In landscape plantings, control of downy mildew on impatiens with fungicides is not practical. Symptoms of Downy Mildew on Impatiens Early symptoms can be hard to spot and might be mistaken for a nutrient problem. If you look at the undersides of these leaves the white fuzzy growth of the pathogen is visible. It isn't a fungus like powdery mildew. Downy mildew of impatiens is caused by the ‘fungus-like’ organism Plasmopara obducens.The group of organisms that cause downy mildew diseases are not true fungi- they are more closely related to the well-known plant pathogens Phytophthora and Pythium than they are to true fungi. To prevent the spread of this disease, water plants in the morning so they have plenty of time to dry before nightfall. As the disease progresses, leaves and flowers drop off, leaving a bare stem. When planting your beds, DO NOT use impatiens in the same areas as you did last year; remember that P. obducens can potentially overwinter as oospores in soil and old impatiens debris. Thank you for choosing this service. Affected leaves often curl downwards. There are a handful of other impatiens species that are resistant to impatiens downy mildew and they are a good option if you enjoy the look of impatiens but don’t want to risk losing your plants to an infection. P. obducens can potentially overwinter in a garden in the form of specialized spores called oospores. The underside of infected leaves will be dusted with what looks like white flour, these are the sporangia. Basils, impatiens, melons, and viburnum are particularly susceptible to downy mildew. On the upper surface, yellow leaf spots will appear angular in shape and bound by leaf veins, sometimes creating a “quilted” look. Start applications before symptoms are present and be sure to read and follow all label instructions of the fungicide that you select to ensure that you use the product in the safest and most effective manner possible. And as always, our dedicated staff is here to help you find exactly what you are looking for. Whether P. obducens can be introduced via impatiens seed is unclear. However, you should only purchase symptom-free plants from a reliable, local nursery. • A white, downy-like growth develops on the underside of leaves. A. For a complete list of impatiens replacements, click here. Unfortunately, there’s little you can do to prevent infection once the sporangia are present. Downy mildew of impatiens, Plasmopara obduscens, has developed rapidly since 2011 on the eastern coast as well. It presents as a white powdery spots on the undersides of leaves, and you’ll also notice yellowing or stippling on leaves, and stunted growth. Copyright © 2020 EG Media Investments LLC. Impatiens downy mildew is caused by the fungus-like water mold Plasmopara obducens. Eventually leaves and flowers drop, leaving you with a plant of mostly stems. These types of impatiens appear to be resistant to or tolerant of impatiens downy mildew. Photo credit: Daniel Davis. Inspect impatiens plants carefully for symptoms of downy mildew before buying them. Because it can live for many years in the soil, if you’ve grown impatiens that showed signs of impatiens downy mildew in the past, you’d be wise to not plant them again for several years. It can also be introduced by windborne spore-like structures called sporangia. Such products are typically available for homeowner purchase at local garden supply centers. Use a fungicide that contains the active ingredient mancozeb and that is labeled for use on impatiens. Save my name, email, and website in this browser for the next time I comment. The downy mildew disease that affects Impatiens spp. The leaves get droopy and eventually white cottony spores will appear on … As the disease progresses, the leaves may look wilted and you may see a cotton-like white film on … You may never even see any powdery mildew like substance under the leaves, but if you do there is no doubt your plants are infected by Impatiens Downy Mildew. Downy Mildew is a very destructive disease leading to the eventual defoliation and failure of impatiens in the landscape. Early Symptoms: • Yellow or Speckled Leaves • Leaf edges curling downward • A white downy-like color on the underside of the leaves Advanced Symptoms: • The plant may look wilted, like it needs water • Premature leaves and flowers dropping, leaving mostly stems Impatiens downy mildew is a pathogen that affects every variety of Impatiens walleriana along with all of the hybrid impatiens that use this species as a parent. Photo courtesy Tina Smith, UMass Extension. Madison, Wisconsin 53706 What is impatiens downy mildew? So be sure to look for signs with this symbol when shopping at Hicks Nurseries for impatiens replacements. What does impatiens downy mildew look like? Downy mildew is caused mostly by organisms that belong to either the Peronospora or Plasmopara genus. The disease affects garden impatiens (Impatiens walleriana and I. balsamina), as well as native jewelweeds (I. pallida and I. capensis). Plant Disease Diagnostic Clinic How can I avoid problems with impatiens downy mildew in the future? Though this disease has been in the U.S. for at least a decade, it’s becoming more and more common. Now, through devoted breeding efforts and collaboration that spanned the globe, PanAmerican Seed offers Impatiens downy mildew resistant Beacon, and with it the opportunity to bring back into production this well-known, in-demand, easy-to-grow, and versatile product for … This will promote good air flow and promote drier conditions that are less favorable for downy mildew to develop. 1630 Linden Dr. Room 183 (The photo on the left isn't impatiens downy mildew, but it gives an idea of what the condition looks like.) It will not infect other flowers or vegetables. Infected leaves may curl downward. Once established in a garden, P. obducens can spread from plant to plant by wind or rain splash. Thankfully, this pathogen only harms impatiens. This downy mildew is unique to impatiens. And irrigate using drip irrigation or soaker hoses, if possible, to keep the foliage as dry as possible. The disease is spread by air currents, … How can I save a plant with impatiens downy mildew? A complete inventory of University of Wisconsin Garden/Farm Facts/Pest Alerts is available at the University of Wisconsin-Madison Division of Extension Plant Disease Diagnostics Clinic website: A diverse plant selection can limit the spread of disease-causing organisms (like P. obducens) and limit the impact of diseases when they occur. One of the first symptoms of impatiens downy mildew is pale, light green leaves. Your email address will not be published. Where does impatiens downy mildew come from? Impatiens downy mildew is caused by the fungus-like water mold Plasmopara obducens. Snapdragons, roses, impatiens, coleus, basil and other crops are susceptible to downy mildew, but each have a unique downy mildew pathogen. Production of sporangia of the downy mildew pathogen occurs on the undersides of the leaves in abundance, can be seen as white patches on the lower leaf surface of what is normally a smooth surface (not hairy). This organism is At first, the leaves of infected plants turn a pale shade of green and curl in a downward direction. See our … Plants such as alternanthera, begonia, coleus, iresine and torenia are possible alternatives to impatiens. For the same reason, avoid overhead watering (e.g., watering with a sprinkler). Plants will start to lose their lower leaves and when you turn the leaf over and look at the bottom it will be dusted with what looks like white flour. Basically, downy mildew is water mold. While this version impacts basil, there are other new variations of downy mildew. She’s the author of five gardening books, including the Amazon-bestseller, How To Make Your Own Cultured Milk Products, Talking Food Forests & Cucamelons With The Farmer Ken, Mushroom Expert Talks Fungal Forms, Cookery, Morels & More, Grow Culinary Herbs For Your Chickens & The Kitchen. Required fields are marked *. As a leader in the garden center industry on Long Island, we stopped selling impatiens walleriana several years ago. There is error while submitting your request. Choose a planting space without a huge block of shade for your impatiens. Initial symptoms include an irregular yellow-green discoloration of leaves that can be confused with spider mite feeding injury. Impatiens downy mildew has been so destructive in many areas that it has made impatiens unusable as a garden ornamental. Thanks to Diana Alfuth, Bill Halfman, Karen Lind, Tom Lind, Patti Nagai, Isael Rubio and José Pablo Soto-Arias for reviewing this document. So impatiens that stay wet for a long time are perfect targets. Impatiens at the Grand Ideas Garden infected with downy mildew. Like many fungal organisms, the pathogen that causes impatiens downy mildew prefers wet weather and travels readily via soil, water and air. impatiens downy mildew is the presence of a fuzzy white material (actually the organism that causes the disease) that develops on stems, buds and particularly the under sides of leaves. Impatiens downy mildew is a disease that has become a serious threat wherever impatiens are grown. The second stage of infection causes white growths to appear on the lower leaf surfaces. Both are resistant to this pathogen. These spores can be found in soil and in infested plant debris. Use a wide variety of bedding plants in your garden. Space impatiens plants as far apart as possible. Where does impatiens downy mildew come from? Credit: UMN Extension – Sporulation of impatiens downy mildew. Q. If you have planted infected impatiens your best bet is to plant an entirely different shade plant for the next several years to avoid constant re-infection from the soil. If you decide to plant impatiens in your garden, consider using New Guinea impatiens or its hybrids. Those also include the double-flowered “rosebud” impatiens, and the Fusion Exotic impatiens. As a last resort, consider applying fungicide treatments for control. An EEO/Affirmative Action employer, University of Wisconsin-Madison Division of Extension provides equal opportunities in employment and programming, including Title IX and ADA requirements. While powdery mildew is cause by a true fungus, downy mildew is cause by parasitic organisms that are more closely related to algae. As mentioned above, downy mildew all but wiped out traditional impatiens, but good news is on the horizon. Your email address will not be published. For more information about Downy mildew, click here. The most distinctive characteristic of impatiens downy mildew is the presence of a fuzzy white material (actually the organism that causes the disease) that develops on stems, buds and particularly the under sides of leaves. *Completed as partial fulfillment of the requirements for Plant Pathology 558 at the University of Wisconsin Madison. Downy mildew symptoms can be very subtle, starting as a slight light green mottling or stippling on one or a few leaves. These plants are likely infected, but not yet showing downy mildew symptoms. Obvious symptoms of impatiens downy mildew may not appear for five to 14 days. Impatiens downy mildew infects common and double impatiens, but does not harm New Guinea impatiens or other plants. Often new infections arrive in a garden from transplants that were not yet showing symptoms. At first, the leaves of infected plants turn a pale shade of green and curl in a downward direction. DO NOT buy infected plants. Early signs of infection may have been leaves that looked yellowish, as if the plant needed feeding, or foliage that curled under or seemed to wilt. If Downy Mildew survives the winter in plant debris in the soil, is it safe to plant other flowering or foliage plants in affected beds next season? Sporangia are spread by air currents, by water splash, and on infected leaf material and seeds. Once you have purchased your impatiens, DO NOT plant them right away. It affects both cultivated and wild impatiens, but not New Guinea impatiens. This document can be provided in an alternative format by calling Brian Hudelson at (608) 262-2863 (711 for Wisconsin Relay). Apply the fungicide per label directions as long as weather conditions (i.e., wet or humid weather) are favorable for disease development. The fungus that causes downy mildew has already swept through Europe, where impatiens are simply no longer a player in the landscape. It spreads easily from plant to plant, especially during wet or humid growing season. Impatiens downy mildew may look like white down on the underside of primarily yellow Impatiens leaves, but can also be found on the underside of green leaves. This disease devastated impatiens to such a degree in Europe last year (2011), that growers and garden centers far and wide stopped stocking them. Peronospora lamii was discovered on coleus in 2005 in New York, and by late 2006 had spread throughout the rest of the country. Impatiens Downy Mildew: Identifying & Managing the Disease. While it may seem … How Downy Mildew Spreads Downy mildew is a strange beast. Impatiens downy mildew is a pathogen that affects every variety of Impatiens walleriana along with all of the hybrid impatiens that use this species as a parent. The most distinctive characteristic of impatiens downy mildew is the presence of a fuzzy white material (actually the organism that causes the disease) that develops on stems, buds and particularly the under sides of leaves. If you enjoy planting shade-loving impatiens in your garden, you might find your plants suffering from a pathogen called impatiens downy mildew (Plasmopara obducens). Plants with impatiens downy mildew are unlikely to recover and can be a source of sporangia that can infect other impatiens plants, as well as oospores that can allow P. obducens to overwinter in a garden. hours, directions, maps), Archived Handouts from Presentations Prior to 2018, Diseases – Broad Leafed Woody Ornamental, IPM Scout School – Diseases of Field and Forage Crops, College of Agricultural and Life Sciences. Eventual death of affected plants can occur. Impatiens Downy Mildew is a fungus disease that attacks “regular” impatiens, i.e. New Guinea impatiens (I. hawkerii) and its hybrids appear to be either resistant to or tolerant of the disease. This Fact Sheet is also available in PDF format: Copyright © 2020 The Board of Regents of the University of Wisconsin System, Contact Us (incl. In your holding area, keep plants from different sources (e.g., different greenhouses) as far apart as possible. For more information on impatiens downy mildew: Contact your county Extension agent. Instead, use a soaker or drip hose to apply water gently to the soil without splashing it onto leaves. Leaves stippled or chlorotic (yellowing) and looking like they need fertilizer. Thankfully, there are lots of beautiful options available. It's a water mold and requires water for its spores to spread, germinate, and infect plants. Eventually all the leaves and flowers drop from the plant, leaving behind nothing but the bare stems which will eventually succumb to the disease, too, and droop to the ground. And yet: Gardens still exist there! That way, if impatiens plants from one source are infected, you can limit spread to other plants. The most distinctive characteristic of impatiens downy mildew is the presence of a fuzzy white material (actually the organism that causes the disease) that develops on stems, buds and particularly the under sides of leaves. The Downy Mildew strain infecting Impatiens attacks only Impatiens walleriana and a few species of wild impatiens. © 2020 the Board of Regents of the University of Wisconsin System doing business as University of Wisconsin-Madison Division of Extension. 608-262-2863, University of Wisconsin Garden Fact Sheets. Breeders from Pan American Seed have developed a mildew-resistant I. walleriana . Try New Guinea impatiens (I. hawkerii) or SunPatiens, two darker-leaved impatiens varieties with prolific, brightly colored flowers. New Garden Landscaping and Nursery shows you the end result of an outbreak in impatiens beds. Cool, wet/humid weather favors disease development. The disease has recently become a serious issue in the United States, including Wisconsin. Although the disease was discovered in some wild impatiens (jewelweed) as far back as 1897 in Vermont, in recent times it has only been since 2002 that the pathogen first appeared in Britain. What does Impatiens Downy Mildew look like in the landscape? It does not affect New Guinea and Sunpatiens. Another option, of course, is to skip the impatiens and plant a different shade-loving annual in their place. Impatiens downy mildew, caused by Plasmopara obducens, attacked many New England gardens in 2012. Remove and destroy infected plants as soon as they are noticed to reduce the spread to healthy plants and minimize the amount of … Please let us know a convenient time to call you on, (*All time slots are available in CDT zone.). What Does Impatiens Downy Mildew Look Like? If you see impatiens downy mildew, remove symptomatic plants (roots and all), place them in sealed plastic bags and throw them away in the garbage; DO NOT compost these plants. Also consider removing all impatiens within a three foot radius of symptomatic plants. This is an important distinction to understand because many of the traditional fungicides used to … Our experts will call you on your preferred time. Now the disease is here (and was almost certainly here long before the first official sightings) and it's our turn to adapt. All rights reserved. If you see that at all – don’t buy any impatiens! IT IS NOT A PROBLEM ON NEW GUINEA IMPATIENS, just the common bedding impatiens, double impatiens, and fusion impatiens (walleriana varieties). Do not space plants too closely to ensure they have good air circulation as well. You can try growing them in a different garden area, but depending on the weather and the prevalence of the disease, you could face a new infection. "Beacon" will be available in stores starting fall 2019. Where does impatiens downy mildew come from? Downy mildew starts on the underside of the leaves and causes them to fade and develop stippling much like that seen with heavy spider mite feeding. is caused by a fungal-like microscopic organism called Plasmopara obducens.