Black Spot (growing, manure, Hibiscus, trees)

[Thyra]

Through my own neglect...and the very wet summer I have BS like crazy
I have pruned and fertilized and have new groth which I will spray with fungicide... but I heard of something called "Agricultural Cornmeal"
If you spread it on the ground under the roses it is suppose to inhibit the spores. Anyone ever try it? I can get it locally from my farm supply store.

[J&Em]

People in organic gardening have recommend using it but none can show it actually works. As far as I understand it is plain old yellow cornmeal. There was a report out a while back that was supposed to validate the use of cornmeal around the base of the rose bush as a preventative. Anecdotal eveidence points to it supporting a "good" fungus that competes with the "bad" fungii. While the yellow cornmeal seemed to offer some control there were a lot of variables that had not been tracked so amounts, moisture and soil type still would need to be tested to see when and where it might be most effective.

As an alternative you may want to try using the "Cornell formula". I have used the "Cornell formula" with some success on other garden plants to keep mold diseases under control. I may be going back to it having just given up on commercial organic control on my bee balm. I'll be trying the homemade version below (formula 2 on the linked page). The original formula was created and tested at Cornell University and does as well as many of the organic commercial antifungals, in fact it has become one!!

The following link is to a group that advocates for growing roses organically and seemed to have some good info that I thought you might want to see.

Good Earth Organic ROSE Care - Mildew and Blackspot Control Options

[sylviatexas]

You can also try spraying with an epsom salts solution.

Best luck!

[bluepacific]

Originally Posted by Trudeyrose

Through my own neglect...and the very wet summer I have BS like crazy
I have pruned and fertilized and have new groth which I will spray with fungicide... but I heard of something called "Agricultural Cornmeal"
If you spread it on the ground under the roses it is suppose to inhibit the spores. Anyone ever try it? I can get it locally from my farm supply store.

Hi Trudy

I was a supervisor and head gardener for a property management company before coming to Europe. I had in my care at one of our properties 300 Rose bushes. I used the unconventional methods for controling powdery mildew on the rose bushes using cow's milk. I used a 20%-30% dilution whole of cow's milk. Sometimes even used the same dilution using "Half N Half". This can be used on other vegtable crops like zucchini, maples trees, and others with a high susceptibility to powdery mildew and other fungus.

Some of the better side effects were it helped also as a foliar feed which built up the immune system and the leaves after you sprayed them would dry clear and shiny. Anyway it worked as a deterrent and control. I spoke to the owner of the company a couple of weeks ago and he said the roses went down hill a few months after I left and have never looked the same since and that was almost 3 years ago. I used a lot of unconventional methods in maintaining the grounds. Mostly just copying nature in the way it works. I also worked with alot of beneficial microbiology organisms in the soil to keep plants healthy. You will find that another preventative is the use of Earthworm castings. Especially in controling White Fly and Powdery Mildew on Hibiscus shrubs.

Chemical controls were only used as a last resort, such as when we had bad "WhiteFly" infestation on a plant that had gone un-noticed for some time. Then the immediate need was to kill off as much of the damaging insects as possible to prevent spread to other plants.

When using chemicals, dilute them further down than what is recommended. It saves money and will usually control things anyway. Also, don't spray on a warm or especially hot sunny day. You'll damage the foliage and will have to wait a bit for it to recover. You might also try certain rose varieties which are more resistant than others.

Here's a link on using milk.
Milk as a Garden Fungicide for Powdery Mildew, Botrytis, and Black Spots (http://www.suite101.com/article.cfm/organic_gardening/78810 - broken link)

You can Google on the net with key words and get similiar information. But it really did work for me.

[Thyra]

bluepacific...thank you..I have never heard of that before!! As of now, most of the leaves have grown back. I fertilized and loosened up the soil and added manure..now just want to get them through the winter. I have pretty much stopped deadheading for the season.
Thanks to everyone who offered help with my problem
Was planning on fungiciding today...think I'll try the milk!!
I have also started purchasing Knockout Roses ...have only had them a few weeks.. but I love them already!!