Yellow spots on zucchini leaves- help!

mpazJanuary 10, 2010

My zucchini plants have these yellow spots on their leaves since they started to grow. Is this a pest? Excess watering? Lack of nitrogen? Or just bugs?

Here's a link to a picture of my plants:


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sunnibel7 Md 7(7)

Hmmm, I can't quite tell from the picture, but all three that you mentioned spring to mind. Have you checked the undersides of the leaves for any visible pest or mildew? I see that the cotyledons (first leaves out of the seed) are very yellow which leads me to suspect that overwatering is the case. And of course, that can lead to the other things you mentioned. You might want to start a new set of plants and water a bit less once they sprout. Good luck!


    Bookmark   January 10, 2010 at 3:41PM
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wayne_5 zone 6a Central Indiana

I suggest that they get plenty of sunlight and not too much water. I had some squash that had small round yellow spots in dark green leaves. They did for mildew on yours.

    Bookmark   January 10, 2010 at 4:05PM
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Thanks Sunni and Wayne!
Actually, I did water them a lot when they first sprouted (learning by trial & error...) so I'm guessing that might be the cause. At least there are no visible pests for now...
Would you suggest watering every other day, or depending on how dry the soil looks?

    Bookmark   January 10, 2010 at 4:15PM
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sunnibel7 Md 7(7)

Definitely use methods of figuring out how dry the soil is to decide when to water. Using a rule of thumb based on time like "every other day" can lead to both overwatering and underwatering plants. How much water a plant needs or uses depends on all sorts of things like how big it is, how much soil it has access to (pot size, close neighbors, etc.), how much light it gets, how high the temperature is, what state of activity it is in (active growth, dormancy, setting fruit, etc.), what the weather has been like, and what variety it is. A rule of thumb takse none of that into account!

Since your little guys are in pots, the easiest way to decide if they need water is to pick up the pot and feel how heavy it is. If it feels heavy, or even still heavy towards the bottom, the plants don't need water yet. If it feels very light, then it is time to water. To ensure that enough water soaks in, put a saucer under them so that water that runs through can be soaked back up slowly- check after about 10 minutes and see if the pot feels heavy- that's enough water, then! Or you can invest in a soil moisture meter, which will tell you if the soil is dry or not. They're pretty cheap and you can use them out in the garden, too.



    Bookmark   January 10, 2010 at 5:01PM
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anney(Georgia 8)


I agree with sunnibel -- trying to water "on a schedule" can result in over- or under-watering as noted. Another way to avoid overwatering your plants when they're a bit larger is to stick your finger straight down into the soil. If the soil is dry down to the first knuckle, it's time to water.

If you are growing them in containers and you have sufficient drainage, you can water until moisture comes out of the drainage holes. That will not harm your plants as long as you don't continually water them.

    Bookmark   January 10, 2010 at 5:13PM
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