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Dealing with Powdery Mildew on Cucumbers & Squashes

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Wondering if you have powdery mildew on squash and cucumbers?

Wondering if those white spots on your squash, zucchini, melon or cucumber is powdery mildew? Before you freak out and decide your crop is a goner, take a look at these:

This is NOT powdery mildew on squash and cucumbers.

The following image is what many think is powdery mildew on squash and cucumbers. But, it’s not. Rather, the slivery-white streaking & splotching radiating out from the veins of this zucchini leaf are natural coloring. It’s not disease.

Not Powdery Mildew on cucumbers

So, if the above image looks like your plant, it’s probably in great shape. But, if it looks like the next photo, you may have a problem.

This IS a nasty infestation.

This spaghetti squash leaf is heavily coated in powdery mildew. So, notice how the powdery-whiteness does not radiate from the veins of the leaves. And, it doesn’t have a distinct silvery pattern. Instead, it begins as spots on both sides of the leaf. And, if it is left in place, the entire leaf will be covered & eventually the entire plant will go ka-put.

powdery mildew on squash

Can you eat the fruits growing on these plants?

Yes, you can eat the fruits from squash with powdery mildew. But, if you don’t deal with the disease fast, your plants are likely to stop producing and die.

So, what can you do if you have powdery mildew on squash plants?

Even with close monitoring, good air-flow and disease-resistant varieties, powdery mildew on squash often happens. Fortunately, there are some ways to keep your plant producing organically.

Try our top ways to keep powdery mildew at bay:

Check your crops often for infestations. And, that means looking under squash leaves for mildew as well as on top. Plus, you may need to look closely. That’s because those early dots of mildew may be small. And, if you eradicate it when the spot are small, your squash and other cucurbits will have a better chance at survival.

Also, don’t just check the plants once a day. That’s because you might miss a spot. So, if you can, check for mildew in the morning and again in the evening.

And, try watering in the morning. That’s because this helps ensure your plants will have sufficient moisture to get through hot summer days without a lot of stress. And stress makes squash more vulnerable to mildew.

Plus, by watering in the morning, any dampened leaves should dry out quickly. This is important because water resting on leaves may encourage disease.

Powdery Mildew on Cucumber Leaf

As well, you may choose to cut out any infected leaves and dispose of them. This does a few helpful things. It thins the foliage and encourages better airflow, which reduces mildew. And, it brings more light to the inner portions of the plant, which can power up the photosynthesis engines. Plus, it does the obvious: removes powdery mildew from the rest of the squash plant. But, don’t remove all of the leaves or the plant won’t be able to feed itself and will likely die.

Want to learn more about designing and growing a great vegetable garden? Join our online Academy for printable garden designs, some of our favorite squash plant varieties and more.

A home remedy that doesn’t really work on powdery mildew…

Many will try making home-grown mixtures of baking soda sprays to keep the mildew away. But, these don’t really work well. And, they may even damage the plant tissues. Plus, anything sprayed for powdery mildew needs to coat all sides of the leaves. And, it needs to be applied very early in the infestation.

6 comments on “Dealing with Powdery Mildew on Cucumbers & Squashes

  1. Jami on

    Thanks for this post. It’s validating to know that a professional gardener still has to contend with powdery mildew on her plants. It always seems like despite my best efforts, my squash and melons always succumb to it.

  2. Garden Mentors on

    It’s one of those things just about everyone battles. Reseeding for succession cropping can sometimes keep the harvest coming even if the earliest plants poop out early.

  3. Nick Sanderson on

    Hi ,my name is nick I have a problem with my cucumbers, I only seem to get male flowers occasionly a female flower .
    What am I doing wrong? I live in Western Australia with very hot summers.

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