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yellow leaves on my green beans

Posted by okiefamily 7 (My Page) on
Fri, May 22, 09 at 19:31

My pole beans, the most mature leaves on the bottom, have turned yellow with tiny grey spots. I pulled them all off and the next day had more, I've done that about 3 or 4 times. Any idea what is causing the yellowing? Is it if from all the rain we had a couple of weeks ago?

Follow-Up Postings:

RE: yellow leaves on my green beans

If it isn't from the rain and cool soils it may be a fungus disease that was encouraged by the rain and cool soils. I didn't have good spinach this year. The soil needed to be cultivated but it stayed soooo wet that there was just no way to do it. The plants stayed stunted and the outer leaves turned yellow. And then as soon as it quit raining, I thought I would cultivate a bit and mulch and already the plants were bolting.

Too much rain is not a good thing.

RE: yellow leaves on my green beans

To add a little more to what Dorothy said, the symptoms you describe are almost always a result of too much moisture.

If you had said the beans had rust-colored spots, that would be a disease called Rust, and a fungicide would be the preferred treatment.

Your description of yellowing leaves with tiny gray spots could be any one of a number of bacterial or fungal diseases that hit plants which have been too wet. The most likely candidate in this high humidity is powdery mildew. The first symptoms of powdery mildew on beans is usually faint spotting on the leaves that turns into a gray, talcum-like growth that spreads from leaf to leaf and can cover the whole plant. As the PM worsens, the leaves yellow and you also may see some dwarfing of the plants. You can treat your plants with sulfur or with any fungicide listed as safe (on the bottle label) for use on beans.

One way powdery mildew spreads is by you touching the plants and inadvertently spreading the disease from leaf to leaf or plant to plant, so be very careful if you are touching the plants. If I have PM issues, I usually wait for the leaves to fall off and then pick them up and dispose of them without touching the plants.

There are a couple of other reasons that bean leaves turn yellow, but they are less likely the cause of the current problem. Those other reasons would be nematodes (generally only an issue in sandy or sandy loam soils and generally not an issue this early in the growing season) or spider mites, but I'd be surprised if you had spider mites right now since they tend to be more of a problem in hot, dry, dusty weather.

If your plants are not too far gone, you can save them from PM and other fungal diseases by applying a fungicide approved for use in edible crops. Just follow the product label's directions and keep your fingers crossed. As long as your plants are still producing new growth at the top, they should not be too far gone to save.

In case you are new to vegetable gardening, you should know that it is always a wise idea to avoid touching plant foliage that is diseased and/or wet because doing so helps spread the disease from plant to plant.


RE: yellow leaves on my green beans

Thanks for your help. I would like to add another variable to this equation, the plants (in the raised beds) themselves are a much paler green thant the same plants I have planted in the ground. Any idea about this?

RE: yellow leaves on my green beans

My best guess is that it one of the possibilities listed below, but Dorothy or George or someone else may have other ideas too:

a) Pale green foliage in a raised bed tends to indicate a lack of nitrogen. It could be the original soil mix in the raised bed was of low fertility.

b) Heavy rains could have leached out whatever nitrogen existed in the raised bed's soil mix. This is especially likely if you used a bagged garden soil mix that contained a granular fertilizer.

c) Although it is almost unimaginable that a raised bed would stay so wet that the plants would be waterlogged and could not take up the nitrogen in the soil, it does remain a possibility, esp. if the raised beds were high in peat moss or bark mulch content.

In all three cases, feeding the plants with a nitrogen fert should help. You could use an organic fert like Dried Blood or Blood Meal, or a chemical fertilizer of your choice. For the fastest results, use a liquid fert like Liquid Seaweed or Alaska Fish Fertilizer, or something like Miracle Grow.

In hotter weather, usually from mid- to late-June onward, yellowing bean leaves can indicate damage from a heavy spider mite infestation.

In very sandy soil, yellowing of leaves can indicate root knot nematodes.

You also can see yellowing of foliage on plants that have powdery mildew, but you should see it equally on all plants that have powdery mildew or similar diseases, regardless if the plants are in the ground at grade level or in raised beds.


RE: yellow leaves on my green beans

Dawn, I think you are right about needing to feed them. I will go looking for fertilizer.

I am very amused with my pole beans because the ones that are growing right along are one I accidentially planted in a hole in my yard. (they spilled in about a 12 in. deep hole a dog had dug, which I subsequently filled in with leaves and dirt.)

RE: yellow leaves on my green beans

Amusing things happen in the garden. My most amusing things have happened under the pecan tree where we have a narrow band of sandy-silty soil where anything can grow if there's adequate moisture. (That's in contrast to the 99% of our property that is red clay.) Here's two of them:

Once, I dug up some cannas that I needed to move and left them in the wheelbarrow. I wheeled the wheelbarrow up under the pecan tree and promptly forgot about it. I guess it fell over and the cannas fell into the existing plants (four o'clocks). Apparently my husband put up the wheelbarrow in the garage. I never gave the cannas another thought....and then, the next spring, all of a sudden there was a huge clump of cannas in the middle of the four o'clocks. The are still there too, having "planted" themselves.

Another time, about three years ago I planted way, way, way too many onions. After I dug them all, I set up several tables underneath the pecan tree and cured them there in the shade. Once they had cured, I put them up in the tornado shelter, garage and pantry for long-term storage. I left a couple dozen Southern Belle Red onions on one table, intending to come back and get them later. I never made it back and there they sat. One day, a cat jumped up on that old, rickety patio table and it flipped over, dumping the onions into the bed guessed it, four o'clocks. I intended to come back and pick them up, but I already had so many onions.....and the four o'clocks tend to be snake-infested, so I never got around to it. The following spring, I remembered them when I noticed onion foliage had emerged from the four o'clocks. I laughed and left them there. Now, every year we have huge allium blooms there and I've enjoyed the flowers more than I would have enjoyed those few onions.

So, you see, some of the most successful plantings are the ones that "plant themselves". I enjoy surprises like that. But, you know, if you had tried to plant your beans on purpose in a very deep hole like that, it never would have worked. It is things like this that make gardening so fascinating.


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