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Organic ways to control mildew, blackspots, and rust

Posted by Strawberryhill 5a IL (My Page) on
Mon, Sep 23, 13 at 13:19

I found a great link on organic ways to control plant diseases. Here's an excerpt:

"pH Up: pH-Up is a generic term for alkaline pH adjustors, used to increase water pH in indoor gardens. They come as either a powder or liquid. Its active ingredient is usually lye (KOH) or potash (K2CO3).

Fungi require an acidic environment to grow and die in alkaline environments. Changing the leaf surface environment from acidic to alkaline clears up the infection. An alkaline solution with a pH of 8 will make the environment inhospitable for the fungus and will stop its growth. "

**** From Straw:

Below are 2 thornless Gina's Roses, picture taken this September 22. They are fertilized with diluted molasses & a tiny bit of gypsum to neutralize the bicarbonates (hydrated lime) in my hard water (pH 8). Zero granular fertilizer, no mulch either. The surface is alkaline clay, pH 7.7. Gina Rose is healthiest among my 55+ roses.

Here is a link that might be useful: Urban Garden Magazine on organic fungicides

This post was edited by Strawberryhill on Tue, Sep 24, 13 at 11:12


Follow-Up Postings:

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RE: Organic ways to control mildew, blackspots, and rust

Compost tea for powdery mildew has been studied scientifically with very positive results reported

Here is a link that might be useful: link to scientific study


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RE: Organic ways to control mildew, blackspots, and rust

Thank you, Henry, for that Phytopathology Abstract on compost tea. Here's an excerpt from Henry's link:

"Application of chemical products on the plant or in the soil kills a range of the beneficial micro-organisms thereby disturbing ecosystem. Compost tea helps to restore and increase the populations of those beneficial micro-organisms."

That's so true. This is what I learned from my experiments:

1) Maintain Nature's balance helps with fungal diseases. Here in my garden, roses buried deep with added soil on top & fertilized with alkaline manure are clean. See articles on soil bacteria suppressing fungi growth.

2) When I mess up nature's balance with acidic mulch like cocoa mulch, acidic alfalfa meal, too much gypsum (17% sulfur), or muriate of potash (salt index 116.2), molasses & vinegar added to pH 8 tap water ... then my roses go downhill.

3) Decayed wet mulch foster fungal growth. The exception is fresh recycled wood chips (with mold-retardant) or treated wood with fungicide.

4) Keep surface dry and alkaline to prevent fungal germination. Sharifa Asma in a pot came down with mildew, thanks my bringing down the pH with molasses/vinegar, gypsum (calcium sullate), and potassium (sulfate of potash). Those sulfate-compounds caused rust to the metal scoop. Sulfate compounds zap soil bacteria if applied on top.

5) Salt in chemical fertilizer drives down potassium. Last year I put Lilly Miller NPK 10--5-4 with chemical nitrogen (salt index over 80), plus sulfur. I induced mildew on Mary Magdalene rose. This year, no fertilizer on Mary M., except for corn meal, she's clean.

6) Both potassium and calcium levels go down with lower pH, per U. Extension sites ... leaves got thinner and wilt in the heat with lowering pH. More diseases when I lowered the soil surface of my pH 7.7 clay.

7) My most healthy and many blooms is Stephen Big Purple rose, fertilized with soluble MiraceGro Bloom Booster (with trace elements), at 1/4 dose to make it NPK 2.5 - 13 - 2.5, rather than 10-52-10. No mulch nor granular dumped on top to mess up microbes balance.

My alkaline clay is tested lowest in P, but the best result is soluble phosphorus with trace elements. Phosphorus mobility is a 1, stays put where applied.

Too much phosphorus burns roots, and stunt plant. I did that to Deep Purple rose by dumping Jobes Organics NPK 2-7-4 (with bone meal). I no longer apply granular fertilizer on the surface, be it gypsum (salt index of 8, with 17% sulfur) ... too much burns root, and kill beneficial soil bacteria, essential for nitrogen-fixation.

Granular fertilizers gunk up on top, kill soil bacteria, plus change the soil chemistry, and make it more hospitable for pathogenic fungi germinaton, releasing spores to leaves.

Too much phosphorus, be it chemical or bone meal, can stunt plant. See pics. at below Purdue University extension: 1) lack of phosphorus, reduced branching 2) too much phosphorus and zero potassium: very stunt plant. The below link is worth seeing:

Here is a link that might be useful: Effect of too little or too much phosphorus

This post was edited by Strawberryhill on Tue, Oct 1, 13 at 12:17


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RE: Organic ways to control mildew, blackspots, and rust

Yes, you are right on the spot, I used to buy bone meal, blood meal, fertilizer of any chemicals or granules time released, so confused about the instructions, the organic way is simple & easy, I love the rain, do not know how much watering is enough for roses especially during the summer, poor roses got burned so bad, I got up early cutting all the good roses to keep them in the vases, right now the time is perfect in Southern California for roses & humans, 70F during the day.

I started the compost for the coming year, mainly veggies & fruits waste piled up at far right corner of backyard, covered more clay dirt & bricks on top. I wonder if I should add chicken manure, just a cup each month, to speed up the process. Please advise. Thanks.

Please find the fragrant Pearl Essence in the 18" pot with Organic Planting mix from "Gardner & Bloome", transplanted from the shady ground mid July, 5 more buds waiting to show off.


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RE: Organic ways to control mildew, blackspots, and rust

Thank you, Seaweed, for the lovely pic. of Pearl Essence ... very nice color.

I found this excerpt from WSU Extension: "If you have too much bedding in your pile and want to help speed up the composting process, adding materials high in nitrogen like grass clippings, chicken manure, and blood meal can help."

•Posted by gardengal48 PNW zone 8 (My Page) on
Wed, Mar 25, 09 at 9:56

Yes, you can use too much, or too much in the wrong place :-) Alfalfa decomposes very rapidly (often recommended to kick-start cold compost piles) and that decompostion generates heat. Avoid applying raw alfalfa (meal or pellets) to the root zone as it can burn roots. Don't add alfalfa to planting holes - keep it as a surface application. "

Here is a link that might be useful: WSU Extension on composting horse manure


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RE: Organic ways to control mildew, blackspots, and rust

Found a great site on Organic Rose growing by a group of Californians. The below link distinguishes between powdery mildew and downy mildew, and how to treat both organically.

Also found this comment in HMF on mildew, see below:

Reply of 8 posted 29 DEC 10 byDave Bang

If you want to get rid of powdery mildew and have more blooms at the same time you can use "pure flower" by HYGROCORP. Its organic and requires 1.5 teaspoon per gallon of water. I personally add one ounce of skim milk per gallon of water. The milk acts as a surfactant meaning it will spread the pure flower over the foliage rather than bead on the leaf and roll off. If you have a rose that is relatively good with mildew you can spray once a month if you have a rose that is a magnet for mildew spray once every two weeks and you will be mildew free. It is better to spray before you see signs of mildew. Pure flower leaves no residue. It is totally clear. See the results below with Black Baccara a mildew magnet.

Here is a link that might be useful: Good Earth Rose Care on Mildew

This post was edited by Strawberryhill on Sat, Sep 28, 13 at 22:02


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RE: Organic ways to control mildew, blackspots, and rust

Found another comment in HMF that distinguished between powdery versus downy mildew:

"Reply of 2 posted 12 MAR 03 by Unregistered Guest

Contrary to what you might think, downy mildew is more similar in appearance to blackspot than it is to powdery mildew. It manifests itself as purple/black patches on leaves. Leaves will eventually turn yellow and fall off.

Downy mildew usually starts at the top of the plant, unlike blackspot, and often occurs when nighttime temperatures are in the 50s or 60s and humidity is high. The spores invade from the undersides of the leaves, unlike powdery mildew."


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RE: Organic ways to control mildew, blackspots, and rust

I check my Gruss an Teplitz, which got mildew for the past 4 months, in full sun. Last month I dumped whole-grain corn meal around the bush, the mildew cleared up immediately. Will post picture once it starts blooming.

Found this comment in HMF: RoseDr. Huey
Reply of 1 posted 18 APR 07 bydiggindirt

"I am not usually an organic gardener unless I find something that works pretty quick. I had PM on Crepe Myrtles several years because of too much shade & sometimes too much rain in spring. One year I sprinkled a good amount of old corn meal (with weavils) around the base of them. They never got PM again. I just had sprayed it once before that.......and usually it took several sprays until they cleared up before weather got hot. I use corn meal around several shrubs now, prone to disease. It just hasn't cured black spot on my rose! :).


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RE: Organic ways to control mildew, blackspots, and rust

I saw the tip of spreading wood ash around roses to prevent rust in Everyrose.com, but haven't tried that. I dump alkaline bagged soils (pH near 8), around my roses for winter-protection. Bagged soils here has wood-ash which make them black, alkaline & hard to wash off.

I found an interesting link on organic ways to control insects and diseases, such as "Mix clay with fresh cattle manure to form a paste and paint the mixture on trunks of trees against codling moths and other pests and to seal cuts on the trees after pruning." Great tip, considering that the Elmer glue I put on after pruning: the rain washed that off. My clay can be rock-hard concrete when dried.

Another interesting tip from the below link: "Targets Insects - spider mites, aphids and caterpillars: One tablespoon of flour diluted in 1 litre of water, splashed with a branch or wiped onto the underside of leaves with spider mites or aphids makes the insects dry out. The remedy should be applied on in the morning of a sunny day and it sometimes needs repeating after 2 weeks.

Flour can be dusted onto vegetables prone to caterpillar attack."

Here is a link that might be useful: Natural controls of plant diseases and insects


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RE: Organic ways to control mildew, blackspots, and rust

Found an excerpt from Washington State University extension: "Bacteria are generally more prevalent in alkaline soils and fungi dominate in acidic soils. This is important because microbes are responsible for the cycling of nutrients ... soil pH influences pathogenic microbes, and growers can adjust pH to manage some plant diseases." See link below:

From Wikipedia: "Legumes such as kudzu, clovers, soybeans, alfalfa, lupines, peanuts, and rooibos. They contain symbiotic bacteria called Rhizobia within nodules in their root systems, producing nitrogen compounds .. "

** From Straw: Soil abstracts showed higher soil pH resulting in more soil bacteria, less fungi. My alkaline clay has plenty of bacteria to fix nitrogen, I don't fertilize my 26 trees, yet they are taller than my house. See picture below of my zone 5a garden, where trees lose leaves every winter:

Here is a link that might be useful: Soil pH and Washington State University

This post was edited by Strawberryhill on Wed, Jan 15, 14 at 12:22


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