What disease/pest do my bean and squash plants have?

Asked August 19, 2020, 8:31 PM EDT

My beans have been looking bad for a while, like they’ve been covered by a layer of fine sawdust that won’t rub off. I noticed many leaves are coated in a fine web on the underside and some have very tiny bugs. Many leaves have shriveled and fallen off. My squash plants seem to be suffering the same fate! What is it and can I help my plants?

Multnomah County Oregon

5 Responses

It's challenging to be specific because the images aren't quite in focus. I do have several thoughts but would first like to see images of entire affected plants and their surroundings.

You can upload 3 images to an email. So, if you have more helpful images, reply again.

I look forward to receiving your images.

I will attach more images!
I think it is a horrible infestation of spider mites!

Oh, my! That's more than what I thought; probably the worst infestation of spider mites I've seen.

In the beans, you may be able to remove the most heavily affected leaves, (the white ones) or possibly and entire vine. Consider the same thing with the squash.

Then, hose off the plants daily for a while. Do so early in the day so that the leaves dry as rapidly as possible, thereby avoiding a host of leaf disease problems. Focus on the undersides of the leaves but, with the current mite population, some are also on the tops of the leaves.

When the temperatures are below 80F, and stay that way through the day, consider using commercial insecticidal soap, and repeat as needed according to label directions.

Good luck!


Thank you for your advice. If I decide to tear out the plants entirely, what can I do to decrease the likelihood that they will return in future crops? I’ve had just incredible bad luck this year in my garden... peas munched to nothing by isopods, tomatoes with mildew and late blight, and now these squash and beans! do I need to give my garden a year off?

This has been a rough year for many gardeners. The wet spring instigated various leaf diseases which have run amok, powdery mildew has had a banner year, and the recent heat has dried out plants, soil, and potting mix much more rapidly than most people realized. Then, too, the light summer rainfall is enough to trigger the perfect environment for late blight.

I think you would do well by removing these heavily infested plants, then immediately put them into the trash. Consider doing the clean up the day before trash collection so as many of the mites go with the debris as possible.

You won't need to do anything special for next year because the mites will be hauled off with the plant debris. Then be certain to keep up with the watering to avoid a new mite infestation.

Here's a link to "Growing Your Own" which provides an overview for vegetable gardening but most is also applicable to growing flowers.
In the planting chart on page 7, you're in Region 2.
Go to https://catalog.extension.oregonstate.edu/em9027 and click "pdf" to download the publication.