Cleaning sooty mold from hostas

[FLBuchholz]

I just got back after a vacation of several weeks, and found one of my hosta beds looking quite bad due to honeydew and sooty mold on the leaves. This is likely coming from overhead, where I have a few oak trees shading the area (aphids or oak scale, perhaps). Has anyone had any luck cleaning this stuff from hosta leaves? The area is really too big to hand wash the plants, so I am hoping for something (a "magic solution") that perhaps I can spray on the leaves via a tank sprayer.

Can anyone recommend a treatment for these oak trees? They are quite large, and not amenable to spraying. Maybe a systemic insecticide? The trees may get the ax this winter if I can't find a solution.

[ViolaAnn]

If you find a solution let me know. I've hand washed a few smaller plants - but then I'm on a garden tour on Saturday. The plants under my oak are just covered.

[FLBuchholz]

ViolaAnn,

Thanks for the encouragement. Here is what has now worked for me. Because I don't yet have long-term data, please use at your own (your hostas) risk.

3 cups (ca. 26 ounces) household bleach
ca. 1 Tablespoon "Ultraconcentrated" Joy (brand) dishwashing liquid ("With fresh lemon scent"!)
diluted up to 2 US gallons with water in a plastic hand-pumped tank sprayer with a spray wand. (You probably should not use a stainless steel tank sprayer because chlorine corrodes stainless steel.)

This was sprayed thoroughly onto all the leaves of the hostas, also spraying away obvious clumps of dirt, leaves, maple seeds, cottonwood fluff and other debris. Then let dry overnight.

One spray-washing with this solution worked quite well to eliminate much of the black spotting and stickiness on Sagae, Sum & Substance, Gold Standard, Inniswood, Honeybells, Shade Fanfare, Hyacinthina, Abiqua Moonbeam, Pizzazz, June, Wide Brim. All were further improved by a second spray-washing. Frances Williams was improved but required a second and third spray-washing for really good results. The treatment removed the blue leaf coating on Halcyon, and did not seem to help much on Golden Sceptre.

[FreakyCola]

Hi and welcome to the forum!

Here's what you get for your trees: "Bayer Tree & Shrub Protect & Feed" in a blue bottle. Costs about $18 & I had to use 3 bottles so it's an expensive treatment, but boy does it work! I've seen bigger bottles of it a little cheaper at Lowes or Menards but I'd rather buy a bottle at a time so I'm not out so much. I think Walmart has it too.

You mix the 3 bottles in 1 or 2 gallons of water & pour around the base of the tree. That's it! You do it once a year. You have to measure the diameter of the trunk then it tells you how much to use based on that measurement.

I first used it about 4 years ago on my 100' tulip tree. It's had aphids ever since we moved here & I just thought the sap was stuff from the tree. Then one year the soot got really bad and was all over my hostas so I talked about it here & someone told me my tree had aphids & that's what makes the soot. Wow, how iinteresting!

I don't remember how soon it started working the first time, but I used it the next two years & haven't seen an aphid since or any soot or sap. But then I forgot last fall and sure enough the sap came back this spring.

I hurried and applied the Bayer but was bummed when it said it could take 3 months to work! Heck, summer would be over by then. So I got my ladder out, climbed up on the roof & shot the leaves with the strongest hose spray I could find every where the hose could reach to knock the aphids off. My neighbors already think I'm nuts since I talk to my flowers and yell KOMODO at my Komodo Dragon Hosta and there was the time I sat out in my front yard for over a week handwashing every hosta due to the soot. The neighbors didn't know what I was doing they just thought I was nuts.

By the way, Bayer Rose & Flower Care gets rid of japanese beetles really well. It's granules you sprinkle around the plant then work into the soil.

Good luck!
Ellen

[ViolaAnn]

What's in that stuff? We have a pesticide ban in Ontario; so unless it's pretty innocuous it won't be sold here.

[Mary Ann]

Is that where you got your user ID from, Ellen? It's so descriptive, and very interesting. Thanks for sharing.

[eastwood2007]

We had a really bad problem with aphids 2 years ago. When I called the extension agent office, he said if I spray a band around the base of the trees in very early spring with a pesticide that had a residual action that it may stop the aphids. Apparently the lay eggs in the ground and they have to crawl up the tree.

I haven't had a problem with them the last 2 years....seems these things are kind of cyclical around here. Also, we had a huge crop of the Oriental Lady Beetles that same year and their main diet is aphids, so that may have done the trick, too.

Also had the guineas out quite a bit this spring, so that may have had an impact, too.