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Does this look like late blight?

Posted by NadineNJ zone 6 (My Page) on
Mon, Jul 11, 11 at 21:37

I'm almost certain my brandywines have been stricken with late blight, but this is the first time it's ever happened so I'd like a second opinion before I pull them up. They were coming along beautifully up until a couple of weeks ago - but at first I thought I was dealing with leaf spot or early blight.

Pic 1: Affected leaves and dark patches on stem

Pic 2: Different plant, same symptoms.

Pic 3: The tops of the plants are still green and healthy.

The plants are absolutely loaded with green tomatoes. I've only managed to get about half a dozen ripe/partially ripe fruits so far, and they were incredible. I'm heartbroken at the thought of having to dump what would have been a great harvest.


Follow-Up Postings:

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RE: Does this look like late blight?

I believe its .
Check out this link

Here is a link that might be useful: Tomato Disease Identification Key


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It does look like late blight?

So far as online photos can identify plant diseases, I would say with a high degree of confidence that this is late blight. I would not say 100% because, again, of differences in photography and verbal description but this one is as close as you can get.

Because of the date and time on your posts I am going to go out on a limb and suggest that this plant (plants?) might be
saved if you act immediately. I am going to differ with Carolyn here and say that I do NOT recommend Daconil in this situation.

Here is what you should use if you can get some quickly enough. It is what I used earlier this year on LB infected plants that are now healthy. Copper soap will kill the LB organism. Soap-Shield is one brand though you will be unlikely to find any to buy under that name except by catalog or online. A friend or acquaintance may have some. There are a couple of other brands. Bonide sells one, as do a couple of other companies. If you need to buy some look for an ingredient list that says "Copper Octanoate 10.0%". If all you can find is a "ready to use" item, the concentration will be much less but Copper Octanoate is the critical item. By the way, this material is registered organic.

Use it according to the directions on the bottle (1 fl. oz. per gallon of water)and if at all possible mix it with a spreader-sticker, again according to the package instructions. I am using Bonide Turbo Spreader Sticker. Apply your spray to "all surfaces" of the plant, i.e. top and bottom surfaces of the leaves, stems, petioles and everywhere else. Apply it again after a couple of days or soon after any rain.

Despite the length of this post, I am writing it in a rather hurried fashion in the hope that I can help you to save your plants. I've more to say on this topic and my experience with it and hope to begin a relevant thread later. For now, I hope you can get going and have good luck.


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RE: Does this look like late blight?

I'm sorry that your plants are not doing well. I couldn't pull mine, I love them too much LOL
Below is a link of what I used and even though it didn't cure the plants it suppressed the LB (or gray mold - still not sure to this day). I'm hopeful that we might be able to harvest some maters after all.

Here is a link that might be useful: Disease control spray


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RE: Does this look like late blight?

@Battalina:

Please take note that I am claiming that my method **DID** cure my plants, that they are now uninfected and doing well and that the initial diagnosis was beyond doubt an infection of Late Blight. Also, that the subsequent disease-free period is on the order of six weeks.


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Note on Natria Disease Control

If you go to the link provided above for "Disease Control Spray", click on "Sizes & Product Labels", then click on the "View Label" button on the bottle photo you can get a better idea of just what this product is and why it didn't succeed all that well.

Page one of the label states that it "Controls...listed diseases"

Page two notes that the product is "Powered by AgraQuest"

Page three identifies the "Active Ingredient:
QST 713 strain of Bacillus Subtilis"

Page four lists the "Diseases Controlled or Suppressed" This list appears to not explicitly claim or identify which diseases are actually "controlled" though it does stipulate certain ones for "(suppression)". Among those are Late Blight and Early Blight. In other words, it doesn't work very well on these. Gray Mold is listed without further qualification.

Pages Five and Six are in Spanish.

AgraQuest is a company that specializes in biological controls and makes a product called Serenade. This product you are looking at either is or is a variant of Serenade. In fact, AgraQuest has had, for a number of years, an agreement with Bayer for distribution of their products.

Now, I use Serenade and I like Serenade but I have had to recognize that against certain diseases it just doesn't work very well. Late Blight is one of those. In fact, I have spoken with an AgraQuest sales rep on the phone and received the open caution that "Serenade DOES NOT CONTROL Late Blight". It "suppresses" Late Blight", which means that it interferes with the fungus' (actually Late Blight is not strictly a fungus) mode of infecting your tomato plant. If you look around on the net, you may find a very clever video animation of just how it does this. But it evidently does not accomplish this suppression with respect to every spore that lands on your plant and, therefore, the infection becomes established and remains active, though presumably slower and less active than without Serenade. And this is why AgraQuest characterizes Serenade as a useful component of a comprehensive control program. In other words, it helps but you need other stuff too.

Finally, I would just add that if you are using a "ready to use" product, i.e. a spray bottle like that shown in the photo, you are going to pay a whole lot of money for a very little amount of Bacillus Subtilis (.074%) and have yourself an extremely expensive program of fungal "suppression".


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RE: Does this look like late blight?

i have confirmed (by a lab at VA Tech through my extension agent)late blight on my outside tomatoes and potatoes. I sprayed them with a copper product called Nordox. however late blight does not spread when temperatures are above 86 and the foliage is dry. with the hot weather we've had its hard to tell if its the copper or the heat saving my plants.
the extension agent also suggested spraying with an epsom salt solution alternatively with copper which i have done.
since the weather has become cooler and wetter i am waiting for the blight to take off again. this is on about 350 plants.


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Whole Lotta Copper

@randy41

I don't want to step into an apparently professional relationship between you and your extension agent, particularly since you appear to be growing on a commercial scale while all I have at stake this year is a few garden plants. However, there are a couple of things to ponder.

I looked up the label for the Nordox products and find that they contain up to 75% copper oxide granules. They rely on a slow release of copper ions to kill the organism. That would certainly be effective but I rather doubt that NadineNJ, Battalina or, for that matter myself, would be able to obtain very much of this stuff. They are also going to rely on the product remaining in place for a long period of time and the Nordox company claims that it does, "Famous worldwide for high retention". Nonetheless, I would expect that you are going to have to re-apply, perhaps frequently and that the product is pretty expensive. I would also tend to wonder what effect there would be on new growth, i.e. foliage developing after your Nordox application.

Another point made elsewhere is the possibility of soil contamination with the copper. It is claimed that the copper will bind with some components of the soil and render you with a toxic field. I did find, some time ago, albeit on a casual basis, an assessment of such a condition in Italian vineyards where they had used Bordeaux mixture for generations. Apparently there was less copper than anyone had expected but still a significant amount. Still, 75% is a whole bunch of copper and, in your shoes, I believe I would wonder about that. Soap-Shield is specified as 1.8% metallic copper equivalent.

Epsom salts? Seems to me as if somebody is flailing a bit here. Look around and you will find people recommending all sorts of things including manure tea and even sour milk. I don't wish to demean anyone, especially as there are lots of highly dedicated people trying very hard to help others and often providing yeoman service under highly demanding conditions. All the same, I think that if I were considering an application of Epsom Salts or anything else, I might like to know a little more about the expected MOA (mode of action) for the product.

I am a bit leery of the statement that "late blight does not spread when temperatures are above 86 and the foliage is dry". I have learned over the years to take such "accurate" claims with a grain of salt. Where does anyone get such a specific temperature point to rely on. Is that field experience or did someone do a lab run in petri dishes with a carefully controlled and constant temperature?
Which temperature is that? The high of the day? The low? The mean or average? I have seen the point made very recently (maybe on one of the Cornell pages, but I can't remember) that the Late Blight organism produces and releases most of its spores at night. My overnight temperatures and, I suspect, yours are a lot lower than 86. Also, when I inspect my plants, usually each morning, I always find the leaves quite wet from condensation.

I too am "waiting for the blight to take off again" and know full well that there will be periods of increased spore development and weather conditions conducive to infection. On the other hand, it is now more than six weeks since my initial application of the copper soap mixture and in that time there have been periods of cooler weather and repeated rainfall, though no long periods of drizzle and humidity. I agree that we all watch and wait with little assurance of the future and that there will be successes and failures to follow. I have put forward my suggestion, possibly too early, in the full knowledge that it requires lots of additional confirmation or falsification. Nonetheless, I wrote it here because I've seen questions posted by people who are rather desperate and I have something that is working for me, at least for now.

Good luck.


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