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I have three large zucchini plants in my garden, and all three have been producing nice fruits for a few weeks. The last couple days, one of them has started to turn yellow and sickly:

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I've never grown zucchini before, so I'm not sure if this is just the natural progression, and the plant's life is over... or if this is a sign of some damage or disease. If it is the latter, can I nurse the plant back to health? Or should I destroy it so it doesn't infect the remaining healthy plants?

EDIT

In response to @EdStaub's answer, here's a new photo of the base of the plant, at three magnifications:

enter image description here

Flimzy
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1 Answers1

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Look at the stem, down near the base. Do you see some distinctive brown-orange sawdust-like material? If so, that's called frass, and your plant is being destroyed by one or more squash vine borers. The wikipedia article is really good, and shows pictures (at the bottom) of what to look for.

We've tried killing the grubs in the stem, with a hatpin and other things, with partial success.

Some varieties of squash have some resistance to borers. I don't know about zucchini, though.

Ed Staub
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