This looks fungal but I'm not sure. Any thoughts?
I don't see any bugs.
It was also on some squash that was near these vines.
Don't know where you are, but if your garden is getting this terrific heat, I would suspect sunscald. Give them lots of water to prevent the other leaves from going the same way,
Thank you. Yes, I'm in northern Virginia. I believe this started prior to the current heat wave.
I forget what variety of green beans.
I have some beans on the opposite side of my backyard in same conditions that are not affected.
The outstanding fact about magnesium is that it is a constituent of chlorophyll, and is essential to the formation of this pigment. As a result, when magnesium is deficient, one of the symptoms commonly shown by plants is chlorosis. Magnesium is also regarded as a carrier of phosphorus in the plant, particularly in connection with the formation of seeds of high oil content, which contain the compound lecithin.
The element seems to be very mobile within the plant, and when deficient is apparently transferred from older to younger tissues where it can be re-utilized in the growth processes. This agrees with the observation that signs of magnesium deficiency invariably make their appearance first on the oldest leaves and progress systematically from them towards the youngest ones. its doesnt look fungal to me.
But magnesium is one of the most abundant elements in the soil and does not tend to leach highly. If one is amending occasionally with dolomitic lime as many gardeners do then it is even less likely to be deficient.
Severe infestation of spider mites. I have the exact same look on my Brugmansia right now, but it's been so hot I've been more afraid to spray than of the mites. At least with Brugs the plant is such a survivor I can defoliate, spray, and they'll bounce back. Beans probably will, too.
No pesticides during the heat.
Use harsh water spray early day, directed as well as you can to the backs of the leaves. Repeat several days in a row, then as needed.
Yup spidermites. They love the bean plants. The beans often seem to be able to outgrow them with little interference, which is the good news. Not so fun to find all over the tomato plants or squash...
Thanks much for taking the time to jot down your thoughts. I did find some very small webs on a few parts of the plant.
Looks like mites I suppose. If they spin some kind of web.
Got it... no pesticides in the heat. Why by the way jean001a?
Why no pesticides during extremely hot weather? Because any time you use many pesticides, you run the risk of causing what is in essence a chemical burn on the plant. Hot weather significantly increases the risk this will happen because the plant is already under a lot of stress.
On a lighter note...
If I can get these to grow, I'll make a mint!
Spider mites be damned.
That explains why they used to crop dust at night in Yuma. We used to fly late on night vision and you could see all the crop dusters. I always thought that it kept the pesticide from drying.
Pt, I vote for mites as well...the webbing would back that up. you can't usually see them, unless the cluster together because they are practically microscopic. If you want to confirm, shake the leaves over some white paper, then smear your finger across the paper, you should see streaks of their squished remains... You may also see the tiny moving dots if you stare at the paper...
If those coors take off, be sure to send me some of the harvest...