Sooty Mold

WILDernessWenJune 2, 2013

I was pleased with the results of using insecticidal soap to exterminate the aphid infestation I had in my garden last month. I sprayed all my companion plants with the soap and JUST H20 on my hostas. All my plants were smiling and very healthy looking. Yesterday morning I noticed that my beautiful 2yr. Rainforest Sunrise looked like it had a brownish gray coating on it. After further inspection all my blues had a similar coating and the list goes on... Spent the entire day googling viruses and am 90% certain it is sooty mold. Aphids+Honeydew+Wind, Cold, Heat, Rain, Humidity, more Rain= Sooty Mold. My backyard is an incubator right now. So, what say you oh wise ones? Should I try the 1/10 soapy water technique, a fungicide, or leave it and let mother nature do her thing? Also, if spraying is recommended would you suggest a broadcast type spray, or individually spray each plant? I'm going to see if I can have my DH spray some of the surrounding trees with neem oil as I know you have to treat the pest first. Perhaps, rock gardens would be a better solution in my wooded backyard. The front yard does not seem to be bothered. Ok, let me have it...... WW

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Steve Massachusetts Zone 5b

No need to spray anything other than water. Just wash it off. If you want to use a dish detergent that would be OK, but you might wash off the wax on your blue Hosta. Just get some gloves spray the mold with water and wash it off.


    Bookmark   June 2, 2013 at 11:15AM
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Thanks Steve, We've had some pretty good long hard rains. Didn't know if adding more water was a good idea. I was hoping that if things dried out the sun would kill it. It looks terrible on my lighter hosta. When the leaves dry out there is a whitish color. I found no answer to this part of the fungus on any webset. Does that sound right? I've got to get pictures, don't expect solutions without you seeing what I mean. I truly thank you again for your reply. Off to wash some hosta. Think I'll take a few pics with my Ipad and see if i can set up through photobucket, whatever. WW

    Bookmark   June 2, 2013 at 11:42AM
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tsugajunkie z5 SE WI

The sooty mold needs the honeydew to survive. If there was some left when the aphids were beaten back then cleaning them will help. If, however, you have aphids in the trees above you dripping the honeydew, you may need to give the trees above a blast of water also.


    Bookmark   June 2, 2013 at 6:14PM
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TJ, thank you. Last year I ripped out all the astilbe in one garden because the aphids were so bad. They do get down near all the nice new foliage on my hosta and the plants just look limp and sad. As soon as the aphids are sprayed off the hosta perks back up. The Farmer's Almanac for May says to start spraying for aphids, but it doesn't say what to spray. Next spring I will be spraying all the trees first, possibly with neem oil. Yes, the sooty mold is definitely on the hosta because of the honeydew. Frankly, it's kinda everywhere. Babka recommended the BugBlaster. I've gone to every garden center and nursery in my area but it appears it is only sold online. I will be buying one for sure. Thanks again, WW

    Bookmark   June 2, 2013 at 9:29PM
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WW, the same situation prevails here, it is so humid, raining off and on, the aphids need zapping, there is already a lot of hot humid air that is not stirring.

What I'm wondering, and consider trying as well, is, can I help the situation by stirring the air with a fan? I pretty much suspect that it is the stagnant air which raises havoc with the hosta. Combining heat and dead still air, with too much moisture not giving the plant or its roots a break, can lead to mildew, or it can lead to .....southern blight. Which can in a matter of a couple of days kill a robust hosta.

It killed my beautiful The Razor's Edge last year in short order. So I'm watching the end of my garden that tends to have stagnant air, no breezes, and check it for southern blight. I thought I saw possible early signs of that on one plant near the same spot where my lost hosta was stricken. So I picked up that pot and quickly moved it to an open area with a better chance of circulation.

Like old southern homes with no air conditioning, only the high ceilings and ceiling fans, they closed the shutters on the sunny side of the house, but kept the breeze moving with adjustable shutters. That's the way I help the hosta survive out of their comfort zone. Moving air is sort of evaporative cooling if it works.

    Bookmark   June 4, 2013 at 12:11AM
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Gee Moccasin, I'm not sure. Perhaps one of the "oldsters" ( meaning having grown hosta for longer) would know about air circulation. From what I've read wind carries fungus and some viruses. We had heavy rain over the weekend and it was 57 today in NE Ohio. Cold and damp. I feel like I'm growing moss, ha! I truly love all your beautifully written comments and great pics. You've given me great "pot " ideas too, wow man. WW

P.S. Should we do a GWF shouting? HEY YOU EXPERTS LITTLE HELP HERE please. There I did it! :)

    Bookmark   June 4, 2013 at 12:59AM
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