Yellow spots on cucumber leaves - can anyone identify? (Pictures)

jeremiahg(9B - Sarasota, FL)June 3, 2009

My cucumbers first started showing large yellow spots on the leaves, now the center of those spots are turning brown. I've included several pictures. I've been researching downy mildew and powdery mildew but not sure what it is, if it is even one of those two. Also looking for a natural way to treat it - should I use copper soap fungicide or something like that?? Thanks for any help!!!

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petzold6596(8b southern NM)

Question: do you have a fine droplet sprinkler near these plants?

    Bookmark   June 3, 2009 at 9:09PM
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jeremiahg(9B - Sarasota, FL)

Yes, unfortunately in our sandy soil, which is pretty much the consistency of a kid's sandbox, that is the only way to get everything well watered. The drip line just waters straight down and doesn't spread.

I have a micro-sprinkler that sprays a very fine mist of water.

    Bookmark   June 3, 2009 at 9:23PM
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The lesions confined by the veins look like angular leaf spot caused by the bacteria Pseudomonas syringae. It's pretty common on cucumbers.

It survives on plant debris so sanitation is a big part of control. It also hangs out in the soil, so rotating out to something less susceptible for a few years would help. If re-planting with cucumbers, it's best to use pathogen free seeds if you can. I'm not really sure how that works in a home owner situation. There are also resistant varieties available.

Unfortunately, there isn't any way to get rid of it now that you have it. You can slow the spread by watering early in the morning to allow the leaves to dry more quickly. Also, only pick fruit when the plants are dry.

    Bookmark   June 4, 2009 at 8:36AM
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