Tomato Problem: Micro Black Spots

ZeckstonMarch 16, 2013

Hi everyone,

I've recently discovered what I suspect is a fungal issue with my seedlings. If you look at the picture, you'll notice lots of very tiny black dots on each leaf. These were organic seeds purchased from a reputable distributer, so I doubt it is from the seed.
The temperature is a constant 75F with a pad underneath and they are under four 4' ft 40Watt white fluorescent bulbs for 19 hours a day at a distance of 3 inches. I think I was slightly over watering them at first because they had leave roll, but that has gotten better. My guess is that it is a fungal issue, but before I look for a solution, I want certainty of the issue. Please, can anyone identify what this issue is. Is it a fungal issue, light, watering???

Very much appreciated.

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I should also mention there just about 3 weeks old.

    Bookmark   March 16, 2013 at 4:49PM
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Ohiofem(6a Ohio)

I've never seen anything like that. What potting mix are you using? Have you fertilized?

    Bookmark   March 16, 2013 at 7:11PM
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I used an organic potting mix combined with vermiculite. It did have a mild nutrient level, and I have applied a diluted vermicompost fertilizer to it once. Do you think its a nutrient issue? Too much fertilizing? I know thats a common mistake but, I've never seen this from over fertilizing.

    Bookmark   March 16, 2013 at 8:45PM
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missingtheobvious(Blue Ridge 7a)

How was the fertilizer applied?

    Bookmark   March 17, 2013 at 12:23AM
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the fertilizer was the liquid collected from a vermicomposter (red wigglers) then diluted in water and applied to the base.

    Bookmark   March 17, 2013 at 3:22AM
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This isn't that unusual.

it could just be anthocyanin that is produced at glandular sites that sit on the leaf surface and form trichomes (scroll down to 'trichomes')

there are some varieties that do that more than others

I would only worry about it if they grow and coalesce.

Here is a link that might be useful:

    Bookmark   March 17, 2013 at 9:20PM
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I always take my seedling off heat pads once they sprout. Are you saying yours still have bottom heat?

    Bookmark   March 17, 2013 at 11:39PM
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Yeah but stays at a constant 75F compared to the 58 it stay at in the house.

    Bookmark   March 18, 2013 at 5:50AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Take the plants off the heat mat. Heat mats are for germination only. Cooler ambient air temps once germinated is no problem for them but overly warm soil is.

While 58 is a bit low - 60-65 would be ideal - it is still better than sitting on the heat mat.


    Bookmark   March 18, 2013 at 10:18AM
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Thanks Dave. Heating mat is now off and I'm wating to see if they recover. Now, they are showing signs of leave burn, where the tips of the leafs are burning. The older leaves are also now turning yellow and, I'm assuming will fall off very soon. I think I may need to just start over, but I dont want this issue to occur again. That is why it is important for me to figure out what this problem is!!! Thank you Dave, Mule and Suncity for your time patience and advice. It is very appreciated.


    Bookmark   March 20, 2013 at 2:19PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

As Mule said the black spots aren't all that uncommon and aren't the real problem. They are just engorged hair follicles for the most part from the stressed transpiration.

IMO the fertilizing regimen is the issue - way too much - given the leaf edges in the pic that were already showing signs of burn.

Not only do young seedlings not need all that, they won't tolerate all that. The so-called "organic potting mixes" alone have been known to cause N burn issues because they insist on including things like chicken manure. And then to that you added all the other stuff. Why all the heavy feeding?

Established plants, fine. Young seedlings, no. They can easily be grown to transplant size with no supplementation at all. Not that it is ideal, but it is possible and done by many with no problems. So I'd suggest laying off all the fertilizer stuff with the next batch if you are going to be using that same mix.

And if you are going to use vermicompost tea then it has to be WELL diluted to almost no color to avoid burning.

Add to that the heat and you end up with highly stressed seedlings with fried, stiff, curled under edges that are working overtime to transpire.

Don't get so caught up in all the "organic" label marketing hype ("organic seeds" and "organic seed starting mix", etc.) that you forget that organics can kill plants too when improperly used.

Are these plants done for? No, not IMO. But I'd transplant them into fresh potting mix - preferably a standard one with no fertilizers - and give them some time to recover. You'll lose some leaves but the plants as a whole should recover.



    Bookmark   March 20, 2013 at 3:49PM
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