I am a beginner veggie Gardner and planted acorn squash for the first time. It was growing beautifully up until about 2 weeks ago when the first leaf started to show strange signs. It slowly turns light yellow and then got white spots. Eventually all the other leaves changed as well. I took a picture hoping someone can help identify and remedy what is wrong. I did not see any sawdust like stuff so I do not think its borers.
Thanks in advance for your help!
That looks like powdery mildew to me, or some other fungal disease. I'm not sure what can be done at this point - it looks pretty advanced. I've heard that foliar spraying with milk can slow the progress, but again, your plant looks to be covered with mildew already. If you have other squash plants nearby, I would maybe pull that one (on a still day and carefully, avoiding spreading spores as much as possible and washing up well afterwards to avoid spreading it) and bag it.
Mildew spores are ubiquitous in the environment; what causes a plant to succumb like this is often some kind of stress (weirdly, not having enough water is often a culprit, even though this is fungal). Another helpful thing I've heard about is aeratedcompost tea applied foliar-ly - but I have yet to put together a good system for that.
I agree: Powdery mildew. This plant looks like its too late to save. It's typical for squash leaves. Watering squash in the evening does not allow time for the leaves to dry. The mildew is able to grow in the moist, cool night air.
Once you see it, remove the affected leaves. Put them in a hot or heating up compost pile. You may prefer to burn them.
To prevent it, you can try lightly spraying the leaves with a mix of baking soda and water, about a teaspoon per quart.
Seed the Mind, Harvest Ideas.
Any time you get water sitting on a leaf like this in temperature over 79 degrees for two or more hours you have the perfect conditions for powdery mildew.
I look for good wind between and around plants and a soaker hose or drip irrigation to water them.
If you are going to water in hot dry weather water in the mornings only.
posted 5 years ago
Thank you all for the replies. In unfortunately looks like I'll have pull them out. I was using drip irrigation and watering twice a day, I think I may have overwatered. Also, I think that I also planted the seeds too close together and each plant did not have enough room. That may have caused it as well. the acorn squash is right near my cherry tomatoes, so I hope that it didn't spread. I actually see some of the white fluffy spores on the earth next to the acorn squash plant stems. Any recommendations of what to do there in order to prevent spreading?
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