Rampant Spread of Impatiens Disease Means Limited Supply

Bad news for most of us:

http://triblive.com/state/pennsylvania/3468332-74/impatiens-plant-disease?fb_xd_fragment#xd_sig=f243f9e8d587e0c&xd_action=proxy_ready&data&xd_rel=parent.parent&relation=parent.parent&xd_origin=http%3A%2F%2Fstatic.ak.facebook.com


By Tribune-Review

Published: Monday, February 11, 2013, 10:21 p.m.
Updated 13 hours ago

PHILADELPHIA — For decades, it's been a rite of spring.

You hop in the car, head for the nearest garden center and load up on impatiens, the best-selling, candy-colored annuals that thrive in shade, mound up like half a beach ball, and bloom their heads off till frost, asking little in return.

But this year, disaster looms.

There will be far fewer impatiens for sale. Gardeners who buy them will be taking a risk that experts say isn't worth it. The plants will probably die, and the shade-loving alternatives being offered up may not cut it for many who depend on the easygoing, affordable impatiens to brighten their summer landscape.

The culprit in this gloomy scenario is well-known in the trade and virtually unknown to consumers: downy mildew, a deadly, funguslike disease that targets the popular garden plant known as Impatiens walleriana.

In 2011, the disease was confirmed in 11 states. In 2012, it was in 34, including Pennsylvania and New Jersey. The damage this year is anybody's guess, but there's no question there will be damage.

“The feeling is, it's really going to be pretty much everywhere,” says James Harbage, research and production leader at Longwood Gardens in Kennett Square.

The news is devastating for gardeners like Myrna Pope.

Over the last 30 years, she has planted thousands of impatiens on her shady 1.5-acre property bordering the Wissahickon in Chestnut Hill. Living without them is unthinkable.

“I'd be hysterical!” she says.

Once the plant is infected by the mildew spores — found in soil, water and winds from as far away as a hundred miles — small yellow spots appear on the tops of the leaves and fluffy white-gray growths on the undersides.

There's no cure, and no affordable, foolproof way to forestall the end. The plant shrivels and dies in a matter of days or weeks, while the offending spores can live on in the soil for a year or two or more.

Cool temperatures, high humidity, and moisture from rain and overhead sprinklers or irrigation systems fuel the spread of the disease. And spores in the ground can survive the winter.

“They've figured it out. During dormancy, they form a very thick-walled spore that's resistant to cold and flooding and drought,” says Gary W. Moorman, Pennsylvania State University plant pathologist. He believes that the downy mildew problem could cripple impatiens production and sales for years.
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There are many other reports and research just thought you'd like to know. Judy

Judy--

I wish I could find the picture i took last year of my Imps.
Towards mid-summer, all the leaves would fall off and leave just bare stems sticking up.
That is what I thought this disease was doing to the plants.

In the article above--it speaks of
" Once the plant is infected by the mildew spores — found in soil, water and winds from as far away as a hundred miles — small yellow spots appear on the tops of the leaves and fluffy white-gray growths on the undersides."

I do not recall anything white and fluffy. Do you? The yellow spots? Yeah--maybe. Not sure....

I think for those people that just CANNOT live without the "look" of Impatiens--may i suggest
Vinca flowers instead? They also come in all the "candy-colored" shades and, from a distance, look almost the same.
One bonus--the Vinca can grow totally disease-free, withstand unfavorable conditions, are somewhat drought tolerant
and are also sold in market packs.

Gita

There will be no impatiens at our house this year. I am using begonias instead and some Vinca which looks good but likes a bit more sun than Impatiens. If you see someone selling certified disease free don't buy those either. I understand that it can be spread by the wind. So you could start out with safe impatiens and still get it from a neighbors garden. I have also been told the the New Guinea impatiens are not affected by this blight.

Well Phooey I have about 100 impatiens seedling sitting on my dining room table right now. I guess we'll see what happens - at least I don't have alot of money invested in them.

Vinca is not an option for those who use impatiens in deep shade.

ladysoth, your seedlings will probably be ok, especially if none of your plants were infected last year, but if one or more looks the least bit "funny" my advice would be to dispose of it! Same is true for any impatiens during entire growing season. When in doubt throw it out.

By the time leaves start to curl and drop, spores are already being produced. The white or grey fluffy growth on undersides of leaves is hard to see without a hand lens, and there aren't always yellow spots. Infected plants don"t look infected until conditions are right and spore production is triggered. If your plants were infected last year those spores are opportunistically waiting to infect a new crop.

To tell the truth, probably the hardest thing for me (and I don't think I'm alone in this) is to immediately get rid of any suspect plant! Wait and see, denial, and plant rescue merit badges are not my friends when dealing with the rapidity with which spores from one plant can spread to many.

Last year our GH Assoc. was to take a garden tour of our place and you probably already know that about a week before we pulled the last infected Imp. As luck would have it I had a 12' row of as yet uninfected Imps and begonias (upwind) in garden. A couple of days before the tour we moved them up to the window boxes and front beds to restore the color for the tour. The healthy Imps we moved didn't even survive the rest of the season. :-{ The annual value of this crop will definitely have researchers and seed co.s working full time for a resistant variety but alas, like American Chestnut and others it may take a long time. Resistant variety's and hybrids are now available for Chestnut, not too bad considering it was introduced in the early 20th century. Ric

from Ball Horticultural http://www.balllandscape.com/tools/_Advice.aspx

Landscaper Frequently Asked Questions Impatiens Downy Mildew

Q. How can I recognize the symptoms of impatiens downy mildew? A range of symptoms is possible. Impatiens walleriana that become infected at an early stage of development are more likely to appear stunted in both height and leaf size, and produce fewer flowers. Early Symptoms Include: Leaves that appear chlorotic or stippled. Some varieties will have subtle gray markings on the top of the leaf. Affected leaves become yellow as the disease progresses. Infected leaves may also turn downward from the leaf margins. A white, downy-like growth containing spores may be present on the underside of affected leaves (see photo). This downy-like growth can sometimes also be found on the underside of leaves that appear normal and green Advanced Symptoms Include: Premature leaf and flower drop resulting in bare, leafless stems that resemble green sticks. Eventually these stems may become soft and the plant will collapse (somewhat similar to frost damage).

*Q. Where has this disease been seen in the United States? Impatiens downy mildew was confirmed in commercial landscape beds in coastal southern California; northeast Illinois; northern Indiana; Cape Cod, Massachusetts; and Long Island and upstate New York in 2011. In late 2011 and early 2012, the disease was observed in landscape beds in south Florida. In April 2012, infected plants were observed in landscape plantings in the Dallas, Texas area. By June 2012, regional outbreaks were being seen in the southeast and along the mid and north Atlantic states. As of October 2012 the disease had been confirmed in 32 states, but only two of those states (Oregon and Washington) are located in the western part of the country.

Q. What environmental conditions favor Downy Mildew? Development and expression of impatiens downy mildew is highly influenced by the weather. Wet foliage, cool (~60°F) temperatures (especially at night), and moist air are ideal conditions for disease development. Symptoms often show up after a period of heavy rainfall or prolonged wetness.

Q. Is the disease more of a problem in beds that are in full shade? Downy mildew is a water mold. As the name implies, it likes and requires moisture to sporulate and cause new infections. Plants in heavily shaded locations where the leaves stay wet for extended periods of time will generally have a higher incidence and severity of disease because moisture promotes infection and disease expression. Disease tends to be worse in: Locations where leaves stay wet for extended periods of time. Very dense beds. Beds receiving overhead sprinkler irrigation, because the foliage does not dry quickly. Plants in more open or sunnier areas with better air movement will generally have less disease because the length of time moisture remains on the leaves is reduced.

Q. If beds are cleaned up thoroughly, can Impatiens be safely planted there next year? Impatiens walleriana replanted into beds with a history of impatiens downy mildew may be at a higher a risk of infection than Impatiens walleriana planted into beds with no history of the disease. Two types of spores are produced that can initiate infection: Short-lived (dispersal) spores produced in the downy-like growth on the undersides of infected leaves. These spores will not overwinter.

continued from Ball Hroticultural http://www.balllandscape.com/tools/_Advice.aspx

Resting (survival) spores produced inside infected stems and leaf petioles. These resting spores, called oospores, have the potential to be released into the soil from infected plant debris where they can survive and potentially initiate new infections on Impatiens walleriana planted into the same beds next season. This is important to know because: Prompt removal of infected plants reduces the risk of oospore development in plant tissue, and thereby reduces potential soil contamination. Impatiens downy mildew can potentially occur in beds with no history of Impatiens downy mildew if wind-dispersed spores blow in from other locations where infected plants are growing.

Q. What should I do with the infected plants that I remove? Avoid placing infected plants into compost piles where the overwintering (oospores) may survive. Bag and discard in a landfill if local regulations allow. Plants can also be buried to a depth below your till line.

Q. If the pathogen survives the winter in plant debris in the soil, is it safe to plant other flowering or foliage plants in affected beds next season? The downy mildew infecting impatiens attacks only Impatiens walleriana and a few species of wild impatiens. Alternative shade-loving plants including New Guinea impatiens can be safely planted in beds with a history of impatiens downy mildew. (For a list of alternative plant recommendations, click here.) Coleus is susceptible to a downy mildew disease, but the downy mildew species that infects Impatiens walleriana cannot infect coleus.

Q. What is your recommendation for fungicides/timing of application for impatiens beds? End of season management in the fall should focus on: Scouting Impatiens walleriana beds for this disease. Promptly remove infected plants Note which beds harbored diseased plants. End of season fungicide applications are not recommended. Next season: Preventative applications of fungicides can provide protection of Impatiens walleriana planted into the landscape next season, but applications would need to continue throughout the season if environmental conditions are conducive for disease development. Drench applications of Adorn and Subdue MAXX exhibited the longest residual efficacy in greenhouse fungicide trials, but drench applications are not always practical in landscape settings. Limited trial data from Florida suggests that soil incorporation of Subdue G into landscape beds prior to planting may provide longer efficacy than foliar fungicide applications. Extreme caution must be taken in rotating fungicides among different chemical classes to avoid the development of fungicide-resistant populations.

Q. Should our grower apply a fungicide next year as a preventative? Growers are being advised on best management practices, which include preventative fungicide applications, in order to continue providing the industry with a supply of healthy impatiens. Fungicides applied by the grower will offer short-term protection, but may not provide a full season of control after plants are moved into the landscape. Healthy plants can become infected by both wind-dispersed or soilborne spores once planted into the landscape.

Q. Does this disease attack both vegetative- and seed-produced Impatiens walleriana? All cultivars of vegetative- and seed-produced Impatiens walleriana are susceptible to downy mildew, but there is no evidence that this pathogen can be transmitted by seed.

Judy--

We were discussing this disease (called it a virus last year) last October.
I found the picture I took of my HB of Impatiens showing bare stems. I though this was the virus
we were all talking about, Now there is mention of Powdery mildew and yellowing leaves.

This same thing, as in y HB picture, has been happening to my Imps for the last two years in beds.

What do you call this? It does not fit the description of the "Downy Impatiens Mildew"...

Gita

Gita, I think the picture of your impatiens from last year is a great illustration of the advanced symptoms of Impatiens Downey Mildew infected plants as described in the Ball Horticultural first questions answer I posted above :

So... in reading through this... if I still want Impatiens on my balcony, am I safe if I plant seed and start my own?

Karen

Karen, I would say safer, not safe.

Your disease free seed grown plants in disease free potting mix/containers could still be infected by spores blown in from other diseased impatiens growing in your vicinity. The likelyhood of that happening would be as low as any grower of impatiens this season as you have already controlled for healthy plant/healthy soil.

To keep them from catching what is going around, keep them healthy and strong.

Surely, much of the popularity of "America's favorite bedding plant" is because most people/landscapers could plant them and totally ignore them and they would still grow, bloom, and perform until frosts did them in, and they came in more colors and got bigger than begonias...for a very small investment of $ and time you get reliably impressive results. year after year, in most zones and soils , etc. Their only draw back was that they didn't do well in full sun! (A nod to Chantell, they also aren't fragrant)

Make sure they have good air circulation, no crowding, and when you water do it early enough so that leaves dry quickly

Be aware of the weather/ temp/ humidity conditions that Downey Mildews love: Warm humid days and cool humid nights with little air movement. If there are any stray spores around, that's when they will manifest. I've actually brought some of my susceptible plants (coleus in my case with Coleus Downey Mildew at large) indoors to protect them from prime Downey Mildew conditions. Last year 2-3 times for a day or two each time mostly in spring. This helped a lot.

You know, now that I'm looking at pics I may have had this on a few of my plants at the end of the season last year. Hard to tell as my impatiens typically start to look pretty bad in fall, but I remember thinking that it was odd because it hadn't been all that cold yet - not cold enough in my opinion at the time for the flowers and leaves to start dropping off. It was just 2 plants tho, in 2 seperate containers. So I'll be sure to put new soil and liners in them this year and hope for the best.

This really sucks for those of us who have large shade beds!

My Impatiens have been dying back for the last 2-3 years--and I had NO idea why all the stems
just got bare in all my beds??? I was blaming slugs....

They looked just like the ones in the HB picture I posted above.

I will miss them too! And--I suppose, i will have to dig up any that have self-seeded.
I will miss them in my garden!
Gita

You are way ahead of me. Thanks for sharing this. I only got my notice today. But, I am a tropical grower so I guess I was down on the list. LOL. Either way, you all have the info and that is what matters. Have a good evening. JB

After reading I have a question. First, I don't grow impatiens due to very dry climate. I used to grow them in Massachusetts years ago without problems.

Having said all that, I do grow roses and wonder if there are 2 different types of mildew. My roses will get mildew early in the season depending on the year. Likewise, hardy garden geraniums. None last year. However, I spray with a funguscide spray that kills the mildew. This is the reason why I asked if there are two types. The rose leaves will have a white covering, then turn brown and die.

For years I have been overwintering a few impatiens -- this year, for some reason, none made it. This must be why.

Blooma, yes there are the Powdery Mildews and the Downey Mildews (and many other types, too)

Your roses get Powdery Mildew (white spots like 'powder' sprinkled on leaf surfaces) likes warm and humid.
Infects a wide range of plants

Downey Mildews form primarily on the undersides of leaves and are grey and 'fuzzy' when they sporate or 'fruit'. Downey Mildews seem to be plant type specific, ie, they sat Impatiens Downey Mildew only spreads to other Impatiens. Thrives in humid cool conditions. Other plants threatened with wide spread Downey Mildews are Coleus Downey Mildew and Downey Mildew of Basil.

Controlling for Downey Mildews in commercial greenhouse production involves a quite elaborate system of applications of a select variety of fungicides in a strict rotational schedule which are preventative measures but not curative.

Healthy plant/infected soil or blown in spores = infected plant and soil and wind borne spores when conditions are right. Evidently, Impatiens Downey Mildew produces two types of spores...one that blows around and lands on other leaves, or splashes up from ground where it has landed by rain watering or soil disturbance. A second spore that can overwinter (They don't know for how long) in soil and plant debris is also produced.

lol, here in the Mid Atlantic we seem to have plenty of growing days with cool or warm humid conditions

Downy Mildew will stay in the soil for 3 - 5 years :-(. Have to be patient to grow impatiens again: http://www.simplegiftsfarm.com/downy-mildew-impatiens.html

Here is a list of shade loving plants that can be used to replace impatience. Very good info: http://www.simplegiftsfarm.com/replace-impatiens.html



This message was edited Mar 2, 2013 8:40 AM

Well, that's depressing. Some of my impatiens had the same look of Gita's. Some, on the other hand, did not -- maybe I lucked into a few with resistance? Or more likely it's just the start of the epidemic. I never have bought them, just continued to treat the ones that self-seeded at my old house kindly.

If you have the time and a long attention span, there is a 50+ minute video here on impatiens downy mildew:

http://www.anla.org/knowledgecenter/premium/index.cfm?view=player&colid=112&cid=364&mfid=5473&StartNum=1

It's really a recording of a lecture and slide show presented to professional growers. The link was provided by a grower/nursery that is in my local area.

Nisi, Thanks I would be very interested in viewing that.
Will you be at the spring swap this year. It's in N.J.?

Holly, I actually came to Dave's Garden yesterday specifically to find out info about this year's swap--and couldn't find a forum for it, or mention of it in the sticky at the top of MAG forum. Just point me in the right direction, because I don't think we should take up too much room off-topic here. Thanks for asking!

So far there is just a place and date. It will be at Jan23's home in Salem Cnty, NJ on May 18th. I would imagine that she will put up a Swap thread in April. Her DIL has had surgery recently and Jan is taking care of her and the family for a few weeks. I doubt she will put up anything till she returns home.

That is the plan, Holly. Thanks for helping!! Figured in would wait til April which would still give a month and a half before the swap.

Bordentown is only about an hour from me, nisi. Straight down 295 til the end. Last exit before the bridge and two miles and you will be there. I'm not savvy about doing threads and continuations, etc, so will rely on everyone's help.

Short of putting out a date and place I wouldn't do more Swap threads till spring. You would want it listed on the Mid-Atlantic Events Thread. If it isn't posted there yet let Critter know that you would like it listed. She will put it up.

My impatiends that I started from seed are doing so well - they are lush and green and about 3-4 inches tall and already getting itty bitty buds on them. I'm so sad to know that they'll probably die not too long after I plant them. They are so easy to start and grow compared to say, wax begonias, which grow so slow you get old watching them. My wax begonias started at the same time as the impatiens are only about the size of my fingernail.

I read that new guinea's are resistant to the downey mildew. I found some seeds at Harris seed and called them to see what they thought. I spoke with one of their horticulturists and she said that the new guineas are not particularly resistant to it, but that the Sunpatiens strain of imaptiens was. So I dunno. I decided not to waste time or money on starting the new guineas, but I'll probably buy some plants and see how they do.

ladysoth

If you did not have the disease in your impatiens last year you should be ok. Just follow some good practices: don't crowd, leave plenty of air circulation, get leaves wet as little aas possible when watering, water in am only, wait until nite temps are consistentlt above 60 to plant out. Plant in containers with fresh soil. or in new areas of garden to minimize infection spread. Keep a close eye and immediately remove any suspect plant.

Sunpatiens worked well for me last year. They are easy to multiply by taking cuttings as I believe they are only available as larger plants (not in 6 packs). They are much sturdier than reg impatiens and handle sun quite well. They are a cross between NG Impatiens and a wild impatiens, See Sakata Seed site for moe info. Good luck.

I did have the disease last year I'm sorry to say.

Wow my impatiens seedlings are already blooming on my dining room table. Hmmm maybe I'll just keep them all as house plants this year!

Lots of background info in todays article! Thanks Carrie

http://davesgarden.com/guides/articles/view/4156/

I did not purchase those gorgeous healthy looking Impatiens at Home Depot this week because this weather ( warm day/cool nite) is the perfect weather for downey mildew to appear. Two other nurseries have large banners about Impatiens Downey Mildew to alert their customers. In effect, these banners say that any Impatiens plants they have are 'healthy' upon arrival, but that since DM spores are air borne and disease is rampant in the area that the plants purchased will likely die. Both banners I saw had large pictures of "sick stick impatiens"

Have you seen Impatiens for sale? Where? Were there any warning signs or banners?

Our HD got some in too. Pretty red ones.

I asked Sue (Bell Nursery) why--and she said that buyers will have to beware--She said that trhey
had some kind of a flyer up--somewhere.

Well__I go out to Garden on my Sundays starting on May 5th. You can be sure i will tell them--
if they ask. Or--even if they don't ask.
I could even print out my photo from last year......where the dead stems are all that's left in my HB.

Coleup--
would you have a good picture that can be printed out to show customers?
I guess i could Google one.......
Also--do you feel that if grown in a pot--on one's patio, away from any beds--
that there is a chance that they would do OK?

Gita

Or Meadows Farms nursery here in F'burg has signs up in the section where they used to keep the impatiens, stating they will not be stocking them indefinitely. They have hand-out flyers and a big poster that describes the fungus/virus, and why they have chosen not to carry impatiens.

I have to say I was impressed! I haven't been to many other garden centers yet this Spring, but I have seen impatiens at Wal-Mart. I will be curious to see if anyone else will "do the right thing" and not carry them.

Karen

I've seen them at the big box stores and larger grocery stores and haven't seen any kind of warning signs. The ones I started from seed are doing well so far but I figure it's just a matter of time. I put them in containers that are sort of our of the way and not seen close up - in the really nice containers that I walk past all the time I substituted New Ginuea impatiens, wax begonias and tuberous begonias. Once monkey flowers are available around here I'll get some of those as well as they always perform nicely.

I bought some at our local Lowe's in May and am hoping for the best. With all this rain I could see a future problem. So far so good.

Lady--

Can't beat Vinca (Perryvincle) for a sub for Impatiens...they even look like them,
come min every color, and bloom all summer. Very hardy--sun or part shade.

There are some beautiful, new colors too... Gita

I have very dense shade and vinca doesn't do all that well for me where I normally use impatiens. Begonias are working fine tho. I do appreciate the suggestion!

Ladysoth: I'm with you on the dense shade -- I used to use impatiens to lighten up the shade. I hadn't thought of using begonias -- I usually put them in pots. I thought they needed more sun than vincas.

This year I've been putting all my budget into perennials and grasses, so no annuals. I should have grown them from seed, but didn't get organized....

Begonias do pretty good in the shade - but they're just not as eye catching as the impatiens and my shade bed it looking a bit sorry cause of it this year.