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Brown spots on lettuce seedlings

Posted by nomatic 7 (My Page) on
Thu, Feb 7, 08 at 21:07

I am a novice gardener trying my hand at vegetables this year. Any help or suggestions anyone can offer would be greatly apprieciated.
I have a flat of Bibb Lettuce seedlings that are about 10 days old growing under lights. I noticed that I have small brown spots showing up on about 50% of the leaves. As far as I can tell the plants look pretty good and are growing rapidly.

I have been careful not to over water these so I don't believe that this is the problem. I used Jiffy seed starting mix so I have to believe that it's not something caused by the soil.

I do remember reading somewhere not to handle tomato plants without washing your hands if you are a smoker. I do smoke so is it possible that transfered something to these plants by touching the leaves?

Follow-Up Postings:

RE: Brown spots on lettuce seedlings

Tobacco mosaic virus is very rare (but possible) but I'd first suspect the more likely villains. Do the spots rub off? If so the problem is a mold from too much moisture. Have you been misting the plants? If so, stop and see if the spots disappear. Is there adequate air circulation? A small fan on low will help greatly. Under lights? Need to be close but not close enough to scorch. Room temps? Lettuce prefers cool temps and thrives in the 50 degree range.

Lastly any chance they are a pest? Aphids come to mind as a common problem with lettuce seedlings. If they can be flicked off the leaves think aphids.

With the Jiffy mix you won't have any N burn going (another possibility sometimes) but you will need to feed them as it has no nutrients. A 25% solution of a water soluable fertilizer works well - nothing stronger.

Hope some of this helps.


RE: Brown spots on lettuce seedlings

Thanks for the response Dave.

I have not been misting the plants. The spots do not rub off, so not mold.
The plants are in my spare room and I have a ceiling fan running on low so there is a light breeze.
They are under 4ft shop lights with cool white bulbs set about an inch above the tops of the plants.
The room temp stays about 60 to 65

As to Aphids.. I don't think so. I am so ready to get out in the yard this year that I am spending a lot of time looking at those wonderful green growing things and I think I would have seen any bugs by now.. :)

Should I be giving them the 25% fetilizer solution every time that I water the plants? I have not done any fertilizer yet, can you suggest a brand name?

Thanks again.

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