Organic disease control methods?

Scott F Smith(6B/7A MD)June 7, 2005

I am doing my first serious tomato growing this year, and I usually do things organically. I have been growing vinafera grapes organically for a couple years now, and I have been moderately successful even though they are famously disease-prone in our hot, humid weather.

Are there any good resources for organic disease control, or lessons you have learned? I am very familiar with the usual organic sprays, namely copper, sulphur, summer oils, and soaps. Also I use seaweed and fish emulsion sprays and have the plants well composted. The best website I found was the ATTRA page, see below. It has a table at the end of disease treatments, but the summary is more or less "copper, copper, copper". In the organic and low-impact grape growing world there are many new disease treatments, i.e. Kaligreen (potassium bicarbonate), phosphorous acid, stylet oil, Serenade, etc, but there doesn't seem to be a similar effort in the tomato world. Or maybe they have tried and there are no big successes so far.


Here is a link that might be useful: ATTRA organic tomato

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carolyn137(z4/5 NY)


First things first.

I think each person needs to know what disease or diseases they're dealing with and then consider the treatments, or in some cases the preventative treatments that might be used.

For some diseases nothing will help, for others something can be used and for most either a synthetic or organic product can be used, with varying results.

So, disease ID first, and then how to address that disease is the way I think about the whole area of tomato diseases and possible treatments.

Does that make sense?


    Bookmark   June 7, 2005 at 3:26PM
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Scott F Smith(6B/7A MD)

Carolyn, I'm not asking about diseases in particular but diseases in general. In other words, I am planning ahead, considering what I may need to buy, anticipating failures, etc. The ATTRA document has what I want in it, lots of information plus a table mapping diseases to organic treatments, but its pretty monomaniacal in that it only mentions copper as a spray (sulphur once as well).

One thing that I would be interested to know is what diseases are more or less untreatable organically (if there are any in that category). For grapes, black rot is extremely difficult to deal with for the organic grower and so it almost falls into that category.

Also, I wonder why there is not more information on organic tomato growing. For grapes and apples, two of my main crops, there are Rombough's and Phillips' very detailed books for example. Is it too hard? Or maybe I am looking in the wrong place.


    Bookmark   June 7, 2005 at 4:20PM
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Hi Scott, I am very interested in organic controls used with tomato growing. Certainly think it is a good idea to know what is out there so you can treat appropriately and without delay. Carolyn, unfortunately you can't wait until you have ID'd a disease to deal with it organically. Many products required are not available locally and must be mail-ordered so you must have the products on hand to deal with problems as they arise or as you mentioned preventatively. Plus it goes without saying that organic methods don't begin with the onset of a disease -- much preparations is needed prior to planting (i.e. solarization, nemacidal cover crops, organic amendments to the soil, row covers, and use of mulches, etc.) all impact future developments of disease and insect infestations.
I am familar with the ATTRA article and as you mentioned not alot of practical information concerning organic controls is given. You mentioned many of the products that I am familiar with but unfortunately I don't know of a single source that deals with tomatoes
I do it backwards sometimes--I look at organic supplier catalogs (, Etc.) and see what is new and then I google active ingredient to find research and studies.
I will list the diseases as best I can that there are controls for in next post as I am pressed for time. Good luck finding what you seek.

    Bookmark   June 7, 2005 at 8:38PM
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carolyn137(z4/5 NY)

Scott and Farkee,

I was making the assumption that a person would have some idea of what disease problems might be encountered where they grow their tomatoes, but maybe that assumption was wrong?

And I wasn't thinking about amendments as in adding organic matter re nematodes, or growing Ebon rye, or things like that.

And I wasn't thinking even of harpin ( messenger) or spinosid, or Soil Guard or products like that either.

I was thinkinbg of products that could be used either preventatively or as a means of possible control for certain known diseases.

I'm very aware that the the whole concept of organic gardening is larger than just products, for I grow organically here at home and also at a nearby garden.

Only at my former 40 min away garden were my tomatoes not grown organically b'c they were grown at the farm of a good friend who does not grow organically.

But this year with the quad muscle injury and being confined to a walker I'm growing only a few tomatoes here at home with the help of two local HS girls. And of course they will be grown organically; the tomatoes, not the girls. LOL.

Carolyn, who will now let the two of you discuss what you'd like to discuss since it appears that my assumptions are not as valid as I thought they might be. And hopefully you'll be discussing some things I might not know about and so could learn even more.

    Bookmark   June 7, 2005 at 9:47PM
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thandiwe2(6b SW Pa)

Really the best organic control for problems with 'maters it the one that Ruth Stout recomended 50 years ago . . .mulch and lots of it. Don't let the soil splash on your leaves and you will have half as many problems to deal with. You may need a copper spray or something else to control airborne problems but clean tomato leaves are just happier. I use leaf mold for mulch at home and cardboard covered with straw at the community garden and it really helps. Even last year when the entire community garden of 80+ gardens lost their tomatoes to blight I was one of the last holdouts and had some plants till frost thanks to the cardboard.

I am trialing serinade solutions and soap-sheild this year so I can't say that they work but ask me next year. I even planted some big boy tomatoes in an underused garden to trial disease control but the soil is lame and I think the poor plants have something wrong with them as they are runty and a bit purple. They don't even look similar to the pretty green and robust plants in my other gardens. I gave them some fish emulsion today --I feel obligated to get them healthy enough for a fair trial.


    Bookmark   June 7, 2005 at 10:26PM
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Scott, there IS a book like the grape book you spoke of but unfortunately very dated (1975). List 30 diseases and how to deal with them organically. It is called "Terrific Tomatoes (All About How to Grow and Enjoy THem)" by the Editors of Organic Gardening and Farming. I believe I got it from the used book dept. Barnes and Noble online. I still think is has value even though there are suggestions no longer valid (ie marigolds interpersed with tomatoes control nematodes-now it is known that only certain varieties help and these must be tilled in). (talking about suggestions no longer valid, while looking for material for you I found a 1966 Extension Bulletin on Tomato Production that recommends DDT and a twice a week spray of parathion and applications of chlordane--the organic movement was just around the corner I guess.)
Another little interesting book with natural controls is "Tantalizing Tomatoes" put out by the Brooklyn Botanic Garden- once again it has a few errors but still very good especially for the beginning grower. (Some of their variety selections might turn the people on this forum into book burners though.) Another book is "Tomatoes" put out by Burpee's and it offers both organic and conventional controls.
Of course, there isn't a book that details the latest in, say, microbials, mycorrhizae application, or beneficial nematodes.

I did find a brochure ,linked below, I think you will find helpful. It lists non-chemical controls and chemical controls of insect and disease problems. You just have to recognize the chemical controls that are organic (and I am sure you can easily do that).
Another one is "2005 Fl. Plant Disease Mgt." Goes through all the diseases and then links you to chemical controls. Unfortunately , you are limited as you said to copper, sulphur, and stylet oils. (
You could try Serenade for tomato blights or go with the old standbys ,oil or copper.
Another very good brochure: Microbial Insecticides (
(I'm partial to U of Fl material as you can see)

whew, the gist of all this, any good guide on tomato diseases will tell you if they are treatable or not--and there are alternatives to conventional control methods (BUT not many).
Cultural practices, therefore, plays a huge role in the organic equation. Farkee

Here is a link that might be useful: Tomatoes-pest management

    Bookmark   June 8, 2005 at 3:07AM
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culdeus(z7 Dallas)

At some point I wish a guy like Howard Garett would release a more comprehensive faq to his methods. I would feel funny basically paraphrasing his methods and his website is not set up well to find things on a quick reference basis.

His brand of organics basically relies on not only using USDA certified organic products, but those that either

)A have a short term effect i.e. strong vinegar for weeds, bt etc.
)Temporarily repellant i.e. hot pepper + soap
)Do not do long term damage to internal soil health

This approach he terms the "natural" approach to organics centers around building soil and plant health through compost, trace mineral applications, foliar feeding, and beneficial insect release.

Clearly his holy trinity of desease fighting would be:

-Cornmeal sowed and cornmeal juice fed as an antifungal
-Garlic tea as foliar feed and drench
-Potassium Bicarbonate as foliar feed

Again with organics you will lose more plants in the first 1-2 seasons. It's on the 3rd-4th as the diversity of organisms build and by following planting diversity patterns that a difference will result. Because of this he rarely reccomends non-hybrids to organic followers just starting out.

    Bookmark   June 8, 2005 at 10:48AM
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Scott F Smith(6B/7A MD)

Thanks for all the helpful information. That Tomatoes-pest management link doesn't have any new treatments, but it does indicate that copper is highly effective -- many growers use it on a regular basis, whether they are organic or not. I might experiment a bit with Serenade and some other things I have around, but it sounds like copper is the way to go generally. Do you ever do a preventative spray of copper? It is easy for me to do since they are in a row right next to my grapes, and if I have some leftovers I can hit 'em with it.

I do have my plants heavily mulched already, around 4" of composted wood chips and leaves. My biggest reason for mulching is water retention, but its good to hear it helps with disease prevention. Last summer I had some tomatoes I did absolutely nothing with, I didn't even stake them up, but they didn't get any diseases until around frost time. They were crawling all over a very well-mulched bed.


    Bookmark   June 8, 2005 at 11:00AM
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culdeus(z7 Dallas)

Copper if used excessively (like more than 2x a year) can lead to destruction of beneficial organisms that would otherwise be fighting disease on their own. That and it can be shown to produce nutrient imbalances and other problems.

Several products have quantities of copper that have beneifical effects beyond what are there. Personally, if I had an acre to rotate around on I'd use copper and let the ground recover. I don't so I avoid copper till the last leaf hangs on.

A product called sul-po-mag contains all the copper you should need for a year and will help build the trace mineral content and release trace minerals for uptake by your plants.

    Bookmark   June 8, 2005 at 11:39AM
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Scott, I think Carolyn would dispute the "highly effective" description of copper. As she has said many times Daconil works better but our choices are limited.

You do have to watch the build-up of copper in the soil-certified organic growers are required to test their soil if using copper. That said, I would hit my tomatoes with it if I was spraying grapes.

THe thing is, once blight diseases get established , I am not sure anything organic helps. (exception-sulphur and powdery mildew).
You are supposed to spray preventatively. It seems to me these things seem to start when you first get little fruit so you could start spraying then. I am not sure how many times it can be repeated.
It would be wonderful if Serenade was effective and you could forget the copper though.
I used Serenade in beginning of year but it was for PM at a friends house and the plant was too far gone but later I applied sulphur and it did help.
I have never used fungicides with any regularity but need to do something next season. I am going to try Serenade and whatever else I can think of. Good luck.

Culdeus, I may try the cornmeal thing again this year--tried it a bit but did not keep up with it. I don't know how the Cornell formula (baking soda +) would help but anything is worth experimenting with. Good luck.

    Bookmark   June 8, 2005 at 12:38PM
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Look, the most likely diseases in this area to cause you any significant problems are fungal or bacterial diseases of foliage. You should first and foremost use good cultural practices to try to minimize the occurrence/impact of these diseases, i.e. mulch, grow resistent varieties, allow for adequate air flow, keep the plants otherwise healthy etc. Beyond that, the most common non-organic way to treat for these diseases is to spray a fungicide like daconil. There are, however, some organic fungicide choices. Both copper and sulphur sprays can be used as organic fungicides, but they have downsides. I've read of some decent results in using the broad-spectrum organic pesticide neem as a fungicide. There's a newer organic biological fungicide marketed as serenade or something like that which looks like it might be promising. Some people will also talk about spraying everything from milk to compost tea to varying concoctions involving baking soda etc. I have my doubts about these, although spraying compost tea certainly is unlikely to hurt the plant. Likewise, sprinkling cornmeal around your plants is unlikely to hurt.

If you're going to grow organically, you need to be able to expect and tolerate some level of unpretty foliage occasionally and you need to not worry so much about "being prepared." Be prepared by building your soil, mulching etc., but don't get all worked up about how you're going to go about treating diseases which may or may not be a problem for you at all.

    Bookmark   June 8, 2005 at 12:50PM
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Marymd, glad you mentioned compost tea as that is another thing I am going to try. I did read positive results from an unbiased source but I can't remember where. Will try and dig it up later. Farkee

    Bookmark   June 8, 2005 at 1:00PM
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Scott F Smith(6B/7A MD)

I did have a tomato garden five or so years ago and it got some sort of disease in mid-summer every year and wiped it out. I was not serious about growing then in the sense that I just stuck the plants in the ground, never sprayed fertilized weeded or anything. But it does indicate that I could be in for trouble. One thing I did this time was to plant each tomato in its own "hole", a 2x2 area of soil worked just for one plant, and I am going to do the same thing next year but put the "holes" in different spots. Back when I was having no luck I was planting the tomatoes in the same vicinity each year, not in the same spot but in the same bed. The way they were dying it looked like a soil-borne disease.

I have used both Serenade and neem on different things. Serenade is a bust as far as my experiences have been, but I used it only a couple times and on powdery mildew only. Neem didn't work so well on caterpillars. Since it is an oil it should probably work on powdery mildew, but I don't know what else.

Anyway I will probably hit the plants a couple times this summer with copper just for good measure, and otherwise just try to keep them healthy with foliar sprays, weeds pulled, etc. So far they are all looking pretty good, with nice leaves and some 1" fruits.


    Bookmark   June 8, 2005 at 1:51PM
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I agree, I was disappointed with serenade on a full blown PM infection but have never tried it religiously and preventively.

THe other problem I have with copper besides it's persistence in soil is it's effect on microbial insecticides with a fungal mode of action. Sure is a balancing act. If any diseases do develop this season, I second Carolyn's advice, get them ID'd , then you know what you are dealing with.

    Bookmark   June 8, 2005 at 2:30PM
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sic_transit_gloria(z5 KS)

This scientific experiment on prevention of early/late blight is very interesting. Seranade was used and was very not very successful.

Here is a link that might be useful: early/late blight prevention study

    Bookmark   June 9, 2005 at 1:31PM
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zolablue(z5 NE)

Hoping someone will see this and help me out so I don't have to post a new thread.

I see some signs of early blight on a couple plants but all looking healthy otherwise. I want to use some Neem oil on these plants for the blight and perhaps on the others as a preventive measure against it. But I also like to use a fish emulsion and seaweed kelp foliar spray to fertilize them and need to do this again.

My question is since I need to do both which one first? Then how long to wait before the other spray? Thanks.

    Bookmark   July 6, 2005 at 10:57AM
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southgeorgia_girl(8b GA)

I have had success this year with regular spraying of Serenade for fungal diseases. Aside from hornworms, fungal diseases have always been my biggest problem. With humidity in the 90% range and temps around 93, fungual diseases have been my downfall.

This year I started Serenade back in April. I spray it every 10 days or so. It has worked quite well for me. It does not do a great job on powdery mildew, but I have had success with baking soda for that.

I grow my tomatoes in raised beds, caged, and heavily mulched with straw and/or hay. I use only compost and fish/seaweed emulsion for fertilizer. I spray Bt if I am going to be away for a few days and can't check each day for hornworms.

    Bookmark   July 8, 2005 at 8:25AM
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Garlic is supposed to be a very effective antifungal plant. Perhaps a spray could be made from it. Also there is an essential oil blend called Theives from the Young Living company ( oil is good for many things, is successfully used for eliminating black mold). When my 10 chickens had sour crop (a fungal infection) I fed them a little garlic and put several drops of Theives in their water on top of putting them in a new environment and they recovered to full health (had been looking very bleak) in a day and a half. I will be making a spray - if it works I will share the recipe. I have 20 tomato plants and have had a lot of rain and humidity in my region lately. Otherwise, their branches are off the ground, which is mulched.

    Bookmark   July 6, 2010 at 6:30PM
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novice_2009(zone 6b)

Wow, glad I read all of these posts. Dealing with what I think to be EB, and about to order serenade to deal with it.
I think it may be too far gone. I removed dx foilage Sunday, and yesterday bottom leaves looked the same. We've had no rain in weeks, I bottom water at the base, so this tells me it's airborne? Not sure.
Would like to try serenade, but sounds better as a preventative measure.
My question is, being an organic gardener, what can I do to avoid EB and other fungal diseases in next years crop of tomatoes?
Also, would an application of cornmeal to my soil help keep fungal diseases in check?
Thanks for any feedback on this,

    Bookmark   July 7, 2010 at 2:54PM
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