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Magnesium Deficiency, not early blight or septoria

Posted by jrslick ks/5 (My Page) on
Tue, Jun 2, 09 at 11:39

I have been trying to investigate this problem and I may have figured something out. While it may be Septoria, or even early Blight. I have been working hard at allowing enough ventilation.

At the suggestion of an answer on another listserv, they suggested a deficiency. Then I read about Magnesium.

I think I may have an answer. I am going to still spray for fungus, but I will also at some magnesium. 1 tablespoon per plant.


Compare that to

What do you think?

Follow-Up Postings:

RE: Magnesium Deficiency, not early blight or septoria

I think just about everyone of my plants have a little of this going on at the very bottoms. It happened last year too. If it is an infection then God help my plants, I could also spray but its not that bad. If it is just a minor Mag. deficiency I would not worry at all, its not going to affect the taste or production.


RE: Magnesium Deficiency, not early blight or septoria

I think it's definitely a micro-nutrient deficiency. Probably magnesium. Possibly iron. The clue is interveinal chlorosis which is what you see there ... yellowing between the leaf veins.

If it were mine, I'd put one tablespoon of Epsom salt (magnesium sulfate) per gallon of water and feed the plants that show that symptom. And I'd add one teaspoon of Ironite or Fertilome iron and micronutrient supplement to each gallon of the Epsom salt solution.

Please note that most micronutrient deficiencies in native sedimentary soils in Midwest are caused by out of balance pH rather than lack of micronutrients in the native soils. To high or too low and the pH can lock up micronutrients. So, you might want to have your garden soil tested and put into balance before your next growing season. Tomatoes like pH just a bit on the acid side ... say 6.0 to 6.8 or so.

But then ...

Now, having said what I said about the picture you show in the original post ...

I looked at some of the other pictures in you album and there clearly seems to be some Early Blight and possibly some Septoria leaf spot going on in other pictures.

But I'll stick to my story regarding the interveinal chlorosis shown in the picture in the original post of this thread.

RE: Magnesium Deficiency, not early blight or septoria

I think I am going to treat both problems. With a fungicide and Epsom Salt. I do have high pH. It is 7.2 in this area. It has been coming down, 3 years ago it was 7.6. The garden area is also very high in phosphorus and potassium.

Thanks for checking them out.


RE: Magnesium Deficiency, not early blight or septoria

  • Posted by kandm 8b coastal alabama (My Page) on
    Tue, Jun 2, 09 at 16:31

Is this chlorosis more common in the older leaves? Are the leaves rolling up? If the younger leaves are more affected then it might be sulfur deficiency.

Here is a link that might be useful: Nutrient Deficiency

RE: Magnesium Deficiency, not early blight or septoria

Well, first, that links to a great resource, thank you, Kandm. It's now stored in my favorites.

If we want to get right down to it ... there are several micronutrient deficiencies that cause interveinal chlorosis.

Magnesium deficiency shows up as interveinal chlorosis on older leaves because magnesium is mobile in the plant and the plant is drawing magnesium up from the lower leaves much the same as the plant will draw nitrogen up from older leaves and leave them yellow (more evenly yellow though).

Iron deficiency shows up as interveinal chlorosis on younger leaves first because iron is not mobile and the new growth fails first because it cannot draw iron from either the soil or the older leaves.

Manganese deficiency shows up the same as iron ... in the new growth ... but is much more rare.

Copper deficiency can cause chlorosis, but it is very rare.

Zinc deficiency also can show up as chlorosis but should show stunting of new growth, decrease in stem length, and all other symptoms as if for lack of auxin to the growing tips.

Sulfur deficiency shouldn't show up at all anywhere in the Midwest down the windstream from a coal-fired power plant. So, I'm kinda ruling that out.

Again, and after reading the OP's comments about his high pH history, I'd temporarily address it with Epsom salt and Ironite and then continue to address the pH until it gets balance below 7.0 and toward 6.8 or so.

Here's a Chart showing how pH affects micronutrient availability.

Here's a Fact Sheet from Ohio State University with some more information about micronutrient deficiencies.

RE: Magnesium Deficiency, not early blight or septoria

I guess I forgot to say that the affected or is it effected leaves are older leaves near the the bottom of the plants. The younger leaves are all looking good. I think that it is a combination of magnesium and fungus. The magnesium compromised the leaves and made it easier for the fungus to set in.

I will update this in a few days after treatment.

THANK YOU TONS for all the valuable information. I really appreciate it.


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