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Joined: Mon Jun 15, 2009 8:46 pm
Location: Carmichael, CA

Black spots on leaves


I have a problem with some black spots on the leaves of some vegetables. These are not the same black spots as those describe as being found on rose bushes. The spots I have are shinny black spots, almost tar like, on both the under and top sides of the leafy vegetables in my garden. The spots are on my chard and lettuce but not on my tomatoes, squash, and cucumbers.

There are no legs associated with these spots. I can pick/scrape them off and they're hard, like a dried resin, or tar. There's no yellow or brown discoloration around the spots. Some spots have very distinctive edges while others sort of fade out, like a mold/mildew.

The garden is newly planted and we've had unseasonably coolish weather the last few weeks (for Sacarmento, CA.) I water each day at 5:00 am for about 15 minutes. I use a drip sprinkler to broadcast the water.

I've never seen these spots before. My gardening problems usually involve snails and earwigs. Any help is greatly appreciated.



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Super Green Thumb
Posts: 25279
Joined: Sun Feb 15, 2009 6:04 pm
Location: TN/GA 7b

black spots on chard and lettuce

Very mysterious... probably why you haven't gotten a response yet. Commonest black spot problem for lettuce would be bacterial leaf spot, which is associated with cool damp weather conditions. You can google it and see what you think. However, I don't think you could peel those spots off and I can't off hand think of anything that would be on lettuce and chard that you could peel off like that.

Sorry we haven't been more help!

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Posts: 44
Joined: Mon Jun 01, 2009 1:04 pm
Location: Massachusetts, USA

It sounds like some kind of insect problem to me: those are most likely droppings from some bug. Some very cursory internet research turned up lace bugs (see, which seem to have a fair amount in common with aphids. From the description, "Feeding results in spotted leaves and dark, varnish-like excrement on the under sides."

It looks like neem oil should be effective in dealing with them, so if your plants look like they're struggling, I'd try that to deal with them. The article notes that they peak in late summer, so if it is lace bugs, it will probably get worse before it improves.

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