Ask a Question forum: Coleus new mildew disease

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Mar 5, 2016 6:05 PM CST
Have any coleus enthusiasts found a cure or treatment for the new mildew disease that is destroying coleus? it just reached my Southern California garden last summer. Unfortunately, I didn't know about the mildew and brought it home on a nursery plant. Now, my entire grounds and all my mother plants are infected.
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Name: Karen
NM (Zone 7b)
Region: New Mexico Region: Arizona Cactus and Succulents Plays in the sandbox Greenhouse Sempervivums
Bromeliad Adeniums Morning Glories Avid Green Pages Reviewer Brugmansias Garden Ideas: Level 1
Mar 5, 2016 6:07 PM CST
Darn, I don't know anything to help, but I love your Coleus garden! That is gorgeous! I hope there is a solution. They are such nice plants.
Handcrafted Coastal Inspired Art SeaMosaics!
Name: Jennifer
48036 MI (Zone 6b)
Cottage Gardener Houseplants Spiders! Heucheras Frogs and Toads Dahlias
Hummingbirder Sedums Winter Sowing Peonies Region: Michigan Garden Ideas: Level 2
Mar 5, 2016 6:08 PM CST
Welcome! KarenKees

I have not heard anything about this. We are still in the midst of the mildew epidemic of impatiens here. Very frustrating. I'll have to research the coleus problem
[Last edited by jvdubb - Mar 5, 2016 6:09 PM (+)]
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Name: Caroline Scott
Calgary (Zone 4a)
Charter ATP Member Plant Lover: Loves 'em all! Peonies Lilies Enjoys or suffers cold winters Winter Sowing
Bulbs Region: Canadian Garden Ideas: Master Level Million Pollinator Garden Challenge
Mar 6, 2016 7:54 AM CST
I wonder if a spray with dilute peroxide would help?
Just an idea---I have no experience with it.
Name: Tiffany purpleinopp
Opp, AL ๐ŸŒต๐ŸŒทโš˜๐ŸŒน๐ŸŒป (Zone 8b)
Houseplants Organic Gardener Composter Region: Gulf Coast Miniature Gardening Native Plants and Wildflowers
Tropicals Butterflies Garden Sages Cactus and Succulents Plant Identifier Million Pollinator Garden Challenge
Mar 6, 2016 7:58 AM CST
Hi & welcome, Karen! Your gardens are magnificent!! I'm blown away!

So sorry to hear the mildew has found you. I heard about this a few yrs ago & haven't bought any new Coleus since. From what little I understand about it, it can't thrive in high temps. The links have some suggestions for treatment.

Here's some info on this awful downy mildew: (worth waiting for the ad, IMVHO)

Some other colorful plants you might like...
Perilla 'Magilla'
Perilla 'Magellanica'
Iresine herbstii (a red plant)
Bloodleaf (Iresine diffusa f. herbstii)
Hypoestes (comes in white, pink, red)
Polka Dot Plant (Hypoestes phyllostachya)
Tradescantia zebrina (purple/green/gray stripes)
Inch Plant (Tradescantia zebrina)
Tradescantia pallida (a purple plant)
Purple Queen (Tradescantia pallida)
Tradescantia spathacea (dramatic purple back of leaves, various pink stripes)
Moses-in-a-Basket (Tradescantia spathacea)
Begonias (too many to paste links to, various rhizomatous, wax, and cane types are amazingly colorful and easy to care for)
Alternanthera (various)
Joseph's Coat (Alternanthera ficoidea 'Partytime')
Ruby Leaf (Alternanthera dentata 'Purple Knight')
Joseph's Coat (Alternanthera ficoidea)
Joseph's Coat (Alternanthera ficoidea 'Red Threads')
Alternanthera ficoidea 'Snowball'
(and many others in the plant database in search for Alternanthera.)
Hawaiian Snowbush (Breynia disticha)
Euphorbia tithymaloides (dramatic pink highlights)
Variegated Devil's Backbone (Euphorbia tithymaloides 'Variegatus')
Bromeliads & earth stars (too many colorful/variegated ones to link)
Aglaonema (Chinese evergreen, many colorful cultivars)
Gynura (a fuzzy purple plant)
Purple Velvet Plant (Gynura aurantiaca 'Purple Passion')
Plectranthus (various variegated ones)
Variegated Cuban Oregano (Coleus amboinicus 'Variegatus')
Plectranthus (Plectranthus discolor 'Green & Gold')
Plectranthus (Plectranthus forsteri)
Stromanthe Stromanthe (Stromanthe thalia 'Triostar')
Codiaeum (Croton)
Croton (Codiaeum variegatum)
Cordyline (Ti plant)
Ti Plant (Cordyline fruticosa) (look at individual cultivars too)

๐Ÿ‘€๐Ÿ˜๐Ÿ˜‚ - SMILE! -โ˜บ๐Ÿ˜Žโ˜ปโ˜ฎ๐Ÿ‘ŒโœŒโˆžโ˜ฏ๐Ÿฃ๐Ÿฆ๐Ÿ”๐Ÿ๐Ÿฏ๐Ÿพ
The less I interfere, the more balance mother nature provides.
๐Ÿ‘’๐ŸŽ„๐Ÿ‘ฃ๐Ÿก๐Ÿƒ๐Ÿ‚๐ŸŒพ๐ŸŒฟ๐Ÿโฆโง ๐Ÿƒ๐Ÿ๐Ÿ‚๐ŸŒพ๐ŸŒป๐ŸŒธ๐ŸŒผ๐ŸŒน๐ŸŒฝโ€โ˜€๐ŸŒบ
โ˜•๐Ÿ‘“ The only way to succeed is to try.
Name: Ken Ramsey
Vero Beach, FL (Zone 10a)
Tropical Plants & More
Orchids Greenhouse Vegetable Grower Ferns Region: United States of America Hummingbirder
Composter Bromeliad Master Gardener: Mississippi Cat Lover Tropicals Plumerias
Mar 6, 2016 8:19 AM CST
That is sure a gorgeous landscape scene, @Karenkees. Three fungicidal products come to mind, Daconil, Immunox, and Neem Oil. I don't grow coleus so you would have to check on the labels to make sure the fungicides are safe to use on them.

Welcome to ATP.
drdawg (Ken Ramsey) - Tropical Plants & More
I don't have gray hair, I have wisdom-highlights. I must be very wise.
Name: Christine
Saugerties, NY zone 5a
Charter ATP Member Region: United States of America Deer Region: New York Birds Cat Lover
Lover of wildlife (Black bear badge) Container Gardener Hostas Tropicals Dog Lover Hummingbirder
Mar 6, 2016 9:15 AM CST
I have never seen such a beautiful coleus garden, I hope you dont loose any. Welcome to the forum
[Last edited by Christine - Mar 6, 2016 9:16 AM (+)]
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Name: Karen
NM (Zone 7b)
Region: New Mexico Region: Arizona Cactus and Succulents Plays in the sandbox Greenhouse Sempervivums
Bromeliad Adeniums Morning Glories Avid Green Pages Reviewer Brugmansias Garden Ideas: Level 1
Mar 6, 2016 10:48 AM CST
Christine said:I have never seen such a beautiful coleus garden, I hope you dont loose any. Welcome to the forum

I agree Welcome!

Handcrafted Coastal Inspired Art SeaMosaics!
Name: Elaine
Sarasota, Fl
The one constant in life is change
Cat Lover Master Gardener: Florida Tropicals Multi-Region Gardener Vegetable Grower Region: Florida
Herbs Orchids Birds Garden Ideas: Level 2 Garden Sages Celebrating Gardening: 2015
Mar 6, 2016 11:27 AM CST
Hi Karen and Welcome to ATP, that sure is a beautiful display of Coleus you've got going. Housekeeping is always the first line of defense for fungus, if you can keep removing every leaf you see infected, as quickly as possible, that will slow the spread, at least. (don't compost them, put in a plastic bag and throw away in the trash)

We've always used a mild baking soda solution to prevent the spread of mildew-type diseases. It works but must be sprayed often since the baking soda is very soluble and if you use sprinklers, it will be rinsed off each time you water, as well as whenever it rains. It works by altering the pH on the leaf surface making it inhospitable to the fungus.

That being said, I also grow orchids outdoors in Florida where we have every fungus known to man floating around in the air. I've "fought the good fight" for 5 years now, to try to use only mild, organic means like Neem Oil, but recently gave up and bought an excellent fungicide that prevents a wide range of fungal attacks. The active ingredient is Thiophanate methyl, the brand I got is Southern Ag's Thiomyl and it is a generic (less than half the price) than the widely used Cleary's 3336 and available on Amazon. It's a systemic so only needs to be used every 6 weeks or so and is rated for use on fruit trees, so the most non-toxic one I could find.

I'm sure you have excellent watering habits, but it's worth saying that watering first thing in the morning is another strong preventative measure for fungus - the leaves dry off during the day and stay dry at night. Never, ever water at night so moisture sits on the leaves through the cool, dark hours. It's an open invitation.

"Success is stumbling from failure to failure with no loss of enthusiasm." โ€“Winston Churchill
Name: Sue
Ontario, Canada (Zone 4a)
Daylilies Birds Enjoys or suffers cold winters Native Plants and Wildflowers Butterflies Annuals
Region: Canadian Keeps Horses Dog Lover Plant Identifier Garden Sages
Mar 6, 2016 11:38 AM CST
Tiffany, I found that link too and I know what you mean about the ad! The article gives some specific fungicide suggestions based on research trials for this particular downy mildew:

"The most effective active ingredients in research trials conducted in New York and Michigan over the years have been mefenoxam (Subdue MAXX as a drench at 1 fl oz/100 gal), dimethomorph (Stature at the high labeled rate of 12.8 oz/100 gal), fenamidone (FenStop at 14 fl oz/100 gal), ametoctradin + dimethomorph (Orvego at 14 fl oz/100 gal), boscalid + pyraclostrobin (Pageant at 18 oz/100 gal), azoxystrobin (Heritage at 4 oz/100 gal) and fluopicolide (Adorn 4SC at 2 fl oz/100 gal), as well as mancozeb (Dithane at 1 lb/100 gal). Used preventively, these materials have effectively suppressed or eliminated symptoms and sporulation of the downy mildew."
Name: Arlene
Southold, Long Island, NY (Zone 7a)
I was one of the first 300 contributors to the plant database! Tomato Heads Dahlias Houseplants Garden Ideas: Level 1 Photo Contest Winner: 2014
Celebrating Gardening: 2015 Plant Identifier Million Pollinator Garden Challenge
Mar 6, 2016 8:17 PM CST
Welcome to ATP, Karen.

Your gardens are breathtaking!

Mar 7, 2016 12:44 PM CST
Thank you every one for all your nice comments and useful suggestions. I'm going to try Neem Oil first. But, this nasty mildew is so bad and invasive that I think we will have to develop a mildew resistant strain of coleus. Your thoughtfulness and encouragement is much appreciated.
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