Leaves on Watermelon, Pumpkin, and muskmelon turned black.

gblack(6a)September 6, 2010

Last night, the temperature dropped down into the 50's for the first time - cold, but no real concern for frost or anything.

This morning when I went out to check the garden I found that most of my watermelons, pumpkins, and muskmelons which are spread out over a section about 75x75 ft, had sections of the plant that had turned black. Not brown or some other color, just black. (Though I did notice my cucumber leaves have a lot more yellow in them now).

I have no idea what would cause this. It would be a group of leaves off of a particular vine, sometimes the majority of an entire section of vine, etc. It seemed random as to where I would find it on a plant. I didn't seem to lose all of any plant. I checked these just yesterday, so all of this happened overnight. It's just the leaves that go black for the most part. The stems and vines are left kind of withered and pathetic looking, but not necessarily black. The leaves though, if affected, are always black. If I didn't know better, I'd suspect frost.

I also have no clue what would affect all of them at once like that. I'd wonder about my water source and contamination, except my peppers, tomatoes, corn, etc. don't show any real signs of issues.

A few more nights of this is all it would take for a total crop loss on my remaining melons.

Any clues as to what I might be looking at?

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jean001(z8aPortland, OR)

Looks like it got cold enough to damage the leaves.

    Bookmark   September 6, 2010 at 5:53PM
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That is typical of frost damage. Sometimes frost damage will show up in a couple of plants and leave others a little ways away unscathed. It was probably a very light frost if it only damaged the top leaves. The fruit is still good though unless you get a killing frost

    Bookmark   September 6, 2010 at 10:38PM
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So I thought it looked like frost damage as well, but what I don't understand is how it could be frost damage. Please educate the ignorant here. It was quite warm that day (in the 80's I believe), and that night it only dropped down into the 50's. How did I end up with frost? There seems to be a lot I don't know about frost. I had thought it would need to be much closer to freezing for there to be a risk...?

    Bookmark   September 7, 2010 at 12:04AM
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jean001(z8aPortland, OR)

It's called chilling damage. Doesn't go all the way down to 32F. Instead only 50 to 55F.

    Bookmark   September 7, 2010 at 1:18AM
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Anything I can do to mitigate it? Is it always an issue at 50 to 55F or only when there's been a large drop to get there?

    Bookmark   September 7, 2010 at 9:57AM
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jean001(z8aPortland, OR)

Throw a blanket over sensitive plants; remove in AM.

    Bookmark   September 7, 2010 at 6:39PM
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You had what we call a patchy frost and I'll bet it was colder that night than you thought.

The air may be cold enough for frost but if the ground is warm enough the frost will just settle on the roof tops and not touch the ground. Sometimes certain things give off heat or there is a warmer spot that keeps frost from settling.

If you are up early and suspect there might have been frost you can water and wash the frost off before the sun hits it. It is the reaction of the sun on frozen plants that does the damage. You can set a sprinkler in the garden on a timer so it goes on just before sunrise, or you can do as jean suggested and cover them and remove it in the morning

    Bookmark   September 8, 2010 at 1:34AM
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tsugajunkie z5 SE WI

Possibly "sudden wilt" but hard to say. Keep an eye on the plants. In the link below scroll down to "Sudden Wilt". Pictures (hard to see) are shown above the malady's name.


Here is a link that might be useful: Sudden Wilt

    Bookmark   September 8, 2010 at 2:09AM
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