Could it be freeze damage? I haven't even planted mine yet.

My guess this early in the season would be freeze damage too, especially since you didn't see anything inside the stems. Like Carol, I haven't planted beans yet.

Melissia, The brown on the plants could be damage from the cold or could be environmental stress from the combination of having lots of wind, some high temperatures in the upper 80s or lower 90s combined with some nights in the lower 30s. It also could be something fungal although it seems a little early for fungal diseases on bean plants. Since you and I only live a county apart, I know your weather probably has been all over the place like mine has been---in the last month we've been as cold as the upper 20s and as warm as the lower 90s and the April winds have been worse than the March winds at our place. That sort of wild swings in the weather can really stress plants.

With the hollowed-out stems of the bean plants, there are lots of things that do that: the larvae of cucumber beetles are one pest that will do it and I've been seeing cucumber beetles for 3 or 4 weeks now, so that would be my best guess. The second possibility would be lesser corn stalk borers, though I've never had them here in OK. If you are growing beans on ground this year where you grew corn last year, that might be the culprit. It also could be Lima bean borers, but they usually are more of a summertime pest than a spring one.

Even though our soil temperatures are warm enough for beans and our high temperatures are too, I haven't sown a single bean seed yet because of the recurring late cold spells that have had our overnight lows dropping into the 30s for 1 or 2 nights every week. (It is driving me crazy not having any bean seeds planted, but the cold nights are too hard on them.) Since you're having so much trouble with the bean plants you already have growing, you might want to replant. Because something is boring into the stems, I'd likely plant them in a different part of the garden if space were available to do so.

I had hoped to be putting bean seed into the ground today, as we set up the trellises for pole beans in the back garden plot yesterday, but with a forecast low of 32 plus frost in tomorrow morning's forecast, I guess I'll wait another couple of days before I plant beans. I'll likely spend today's garden time weeding, mulching and putting floating row cover over the beds yet again. These cold nights are starting to get annoying. I have to be careful how much more I put into the ground now because I'm in danger of running out of floating row cover if I plant too much more before the cold weather ends.

Dawn

I forgot to mention that the beans are in a container in an unheated hoop house. I too, think the brown is from freeze...I first noticed it after a cold spell, but after seeing some of the stems I thought maybe it wasn't from freeze.

Dawn, I did plant two raised beds of beans outside last weekend...I'll see how they did after last night, we didn't get quite as cool as they first predicted.

Thanks, everyone, I'll add more beans in the hoop house In a few different containers and leave these for a couple more weeks and see what they do.

My radishes in one of the containers had aphids...they added lady bugs and green lacewings to the hoophouse so I definitely don't want to use anything that kills the good bugs.