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Impatiens disease becomes hot topic
Plant pathologists say supply chain not affected; spring planting tips for homeowners who want to protect their flowers.
Wed, Apr 04 2012 at 3:37 PM
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INFIRM IMPATIENTS: Plant producers have been putting preventative programs in place to keep supply chains clean since last year’s discovery that a global disease affecting the common garden impatiens had appeared in U.S. landscapes. (Photo: Tom Oder)
With the arrival of the spring planting season in much of the country, the common garden impatiens is an uncommonly hot topic of conversation.
That’s because a disease that has plagued Impatiens walleriana for the past several years in England, Europe, Africa, Australia and Asia was found in landscape plantings in the upper Midwest, the Northeast and coastal Southern California late last fall. Now infected plants have been discovered this year in residential and commercial landscapes in Florida.
The disease, impatiens downy mildew, is caused by a fungus-like microorganism called Plasmopara obducens. Warning signs of infection are stunted growth, off-color, light green leaves, leaf and flower drop, and, eventually, stem collapse, said Mary Hausbeck, a plant pathologist at Michigan State University.
“A tell-tale sign of the disease,” she said, “is a white, downy growth on the underside of the leaves.”
The disease is not new. “It showed up in a significant way in 2004 in the greenhouse industry,” Hausbeck said. “Prior to that, you have to go back a long way to find even a small report about it.” From 2006 until last year, it didn’t seem to be a big problem, she said.
Now, it’s a global problem and causing concern close to home in communities across the country.
After the disease started showing up in several regions in the United States in late August and early September last year, Ball Horticultural Company in West Chicago, one of the nation’s largest producers of plants for the U.S. horticultural trade, issued a nationwide alert.
“We wanted to make landscapers aware of the problem so they could pull any infected plants out of the ground before they collapsed,” said Colleen Warfield, corporate plant pathologist for Ball.
One of the mysteries about the disease is how it got to Florida. Plant pathologists aren’t sure, Warfield said.
It’s been suggested that “snowbirds” going to Florida homes for the winter could have unwittingly taken infected plants with them, she said. She also pointed out that the airborne spores could have hop-scotched their way to Florida on wind currents from infections in the Upper Midwest. “Spores of another downy mildew species have been projected to travel as much as 600 miles in 48 hours given the right environmental conditions,” Warfield said.
Regardless of how the fungus got to Florida and despite the possibility the airborne spores could drift from infected landscape plants to nearby commercial growing ranges, Warfield offered words of comfort to gardeners who will be looking for impatiens in nurseries this spring.
“There is no evidence the integrity of the supply chain has been affected,” she said.
That’s because plant producers have very rigorous management programs and U.S. suppliers and finish growers are now better informed and have been putting preventative programs in place since last year’s discovery that the disease had appeared in a significant way in landscapes in the United States, Warfield said.
Warfield emphasized that she does not believe any infected plants are knowingly being shipped for sale to either commercial landscape installers or to the general public.
Aaron Palmateer, an assistant professor of plant pathology at the University of Florida, agreed with Hausbeck.
“I was in two large production facilities in Miami-Dade County looking for diseased material to study in the lab,” Palmateer said. “But I didn’t see any. The only diseased material we found was in the landscape.”
“I don’t foresee any shortfall of clean plant material (of Impatiens walleriana) this year,” he added.
Hausbeck offered a similar forecast for Michigan’s bedding industry, saying she thinks growers there will have a good production year for Impatiens walleriana when spring planting season arrives. In some places it’s still too cold to plant. “The high here today is just 39 F,” she said recently from East Lansing, Michigan.
Warfield said it will help put gardeners’ minds at ease if they to understand a few characteristics about the disease. Those are:
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It is specific to Impatiens walleriana. It does not affect New Guinea impatiens or SunPatiens.
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The pathogen cannot infect other garden plants.
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There’s no evidence the pathogen is transmitted to the plant by infected seed.
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The pathogen also produces survival spores that can persist in the soil. They are released into the soil when infected leaves drop or stems collapse, which is one reason why it is important to promptly remove infected plants from landscape beds..
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Because of the possibility of survival spores in the soil, it’s a good idea to not plant impatiens walleriana in a bed this year where infected or suspicious-looking plants of impatiens walleriana were planted last year.
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Plant pathologists have no idea how long the survival spores could live in the soil. “Those spores could survive at least five to eight years in the soil based on studies of other downy mildews,” Warfield said.
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Geography plays a role in where the disease takes hold. “It doesn’t like hot temperatures or dry conditions,” Warfield said. Favorable conditions usually occur in early spring or late fall when temperatures drop at night and there is excessive moisture from rain or humidity. These are the conditions that existed in the upper Midwest when the disease was detected in the United States last fall, she said.
For those who grow Impatiens walleriana, Hausbeck suggested a simple precautionary step: “Keep garden tools visibly clean to the eye,” she urged. “Get the soil off. This is what harbors the survival spores.”
Garden sanitation steps she recommends include:
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Making potentially infected beds the last beds you work on during garden work days.
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Washing tools with a strong stream of water.
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Cleaning tools with soap and water and … cleaning them again.
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Disinfecting tools with a solution of 10 percent Chlorox and water (if you want to be extra careful).
Gardeners who suspect they have infected plants should put them in sealed bags and dispose of them through municipal trash collections. These plants should not be composted.
Gardeners should also not try to cure an infected plant, Palmateer advised. “The disease is too aggressive,” he said. “You have to throw diseased plants out.”
For those who might decide not to plant Impatiens walleriana this year, some alternative shade-loving plants that would also provide summer color are:
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Begonias
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Coleus
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New Guinea impatiens
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Torenia
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Iresine
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Alternanthera
Have other tips for growing impatiens? Leave us a note in the comments below.
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Here in Michigan, my plants that are in the shade all just disintegrated overnigh the 2nd week in August. All the plants in pots and in the sun are doing fine so far. I am replacing with perennials, but it's slim pickings for continuous blooming shade perennials. For the sun, I've chosen butterfly weed and creeping phlox and chrysanthemums, so I have early, mid and late blooming in 3 different heights. Anyone with shade flowers, I'd love to hear from you.
Deb, I also live in Michigan and all of my ground impatiens did the same thing as yours did at the same time! I have about 12 potted impatiens that are doing ok. I planted some in an old cast iron sink that we've used for years as " yard art " and those are doing fantastic.
I planted some really cool Coleous this year called King Coleous, it has beautiful color and even a purple flower in the center. They do really well in the shade.
I live in nutley, new jersey. I have lost 80% of my impatients already. I have planted them in the same spots for the past 16 yrs. and they have done great. This year they started off slow and then just died. I had noticed a white powders substance on them. Does anyone know if i remove the soil and put down new soil if I could plant again next yr.
Live in Connecticut. Planted impatiens on my deck boxes for the last 25 years. Always beautiful. This year they all are dying.
Will the soil need to be repaired so this doesn't again? Is there a way to detect the desease before purchasing?
I live in central CT, and about 3/4 of my 80 impatiens have been wiped out. The light pink have been most susceptible. The white and hot pink held up better, but they are all looking pretty sorry now. This is a big disappointment.
I live in Sout Eastern PA- My impatients are dying out- leaves falling off, and disentegrating stems. They are getting light in color instead of nice rich green. I thought the rabbits were eating them or an insect!
I have planted impatiens around my pond every year for ten years and never had a problem until now. At the moment I am typing this, they are all dead except for a few stragglers. I'm wondering whether I should switch plants for next year. Impatiens used to be the most popular for beds here on Long Island, NY. It seems the past few years landscapers have stayed away from planting them and I might too. It's really a shame though.
I had the same problem with my impatiens this year on Long Island. My wife and I planted three flats, 95% are now dead. We also planted New Guniea impatiens, which are doing just fine. I had thought the problem was from overwatering. Two of my neighbors have landscapers who pulled out the impatiens in July and replaced them with begonias.
I Live in NJ
and lost of of my 10 flats of imaptiens. Never seen anything like this!!!
Planted white and red impatiens in May as we do every year. They were doing well until about a week before the 4th of July. Then the whites started dying off at the ground. Lost all of them. The reds struggled for a while, but are hanging on. Plants in window boxes are doing very well - both white and red. No sign of the downy mildew on the leaves. Am thinking it could be the mulch I used on the beds and not on the flower boxes?? But why did just the whites die off in the beds?
Same here Bob ,... my window boxes are fine as well as one of my clients! Impatiens in the ground are dying from the disease and window boxes are thriving! I think it may be because the window boxes drain out completely. In the ground, the moisture is contained and in more conducive to the virus. That's my explanation anyways.
Could it have been the unusually hot summer and lack of shade for the ones in the beds? I find the white impatiens tend to be more sensitive if they aren't soaked in water constantly in the heat.
Hi,
I live in southeastern Massachusetts, and the downy mildew got to my impatiens starting in early July and has continued. I have thrown in the towel at this point, as it's now spreading across beds that are not connected.
This is very disappointing, as July through September is when the beds of impatiens look their largest and fullest typically in this area... and now they are half dead.
I live in Southeastern Connecticut. I lost 50% of the impatiens planted this year. Three were in pots on the deck, the rest were in a raised bed. So far my window boxes are fine and so are several others planted in pots. We sprayed them several times with a anti fungal solution but the plants were to far gone by that time. It is amazing how quickly this happened, fine one day and dying the next.
We live in NE Ohio and we have nearly lost all our impatiens now, thought it was the groundhogs eating the leaves because it's been so hot, but now it looks like it's a fungus (white fuzziness on underside of leaves) wish we'd known that there was a problem before we spent so much time and money on them. :C
Hi it's me again from Long Island. Please read further research about not planting impatiens for two years in the contaminated soil. Ii read that we need two good cold winters to kill off the fungus spores (I think I understand it that way). Hope this helps to heal the soil but have certainly enjoyed the mild winter.
It looks like I have the same problem on Long Island. I didn't know what was happening until I read this article. My plants were doing great. 2 months later they were disintegrating. I tried fertilizing and changing the soil. It didnt matter if they were in the ground or in pots. Nothing worked. My red ones seem to be doing better (for whatever reason), but I'm not sure for how much longer.
I live in South Jersey and for the first time in 25 years all 8 flats of the Impatients I planted died. I was heart broken and had no idea what happened. I am so glad a friend forwarded this article to me. We have friends who also had the same thing happen with their plants and we both purchased our flats from the same local garden center. I hope this isn't going to be a permanent thing. If anyone else had this problem in my area I'd appreciate it if you would let me know. Thanks.
I am having the same problem. I am losing all my impatients. I have planted them in my deck planters every spring for 10 -12 years without a problem. I live in Monmouth County, NJ. I spoke with my local garden center this week. He told me what was happening. He said I should not plant impatients next year.
all long island has it..my entire community pulled out all impatiens..ive never seen anything like it
I live in Long Island, planted 14 flats and now less than 4 weeks later, have had to tear out all 14 flats. On top of that, the WEEDS have over taken our gardens along with the horrible dead impatiens. More weeds than I have ever seen in our garden in 30 years. Lack of cold this winter was the contributing factor for the excess weeds and the crab grass too!
First year in 32 my impatiens are lost. They started out magnificent. What a shame. Any treatment to the soil to prevent a recurrence in the upcoming years.
there were no impatiens available in Florida in February 2012 when we were at our winter residence...the nurseries ther took them off the market. Here in Cincinnati we put in our usual 200 plqnts in May. and they all succombed to the disease...so much for the Mother Nature Network's assumption that the diease had not reached grower's facitities. Our entire neighborhood is decimated.
Lost my entire bed of impatiens ...very expensive....I could cry !!!
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