From the picture, it looks like the plant went through a period of drying. At the area where the "white stuff" is, it looks to be a bit thinner in diameter than the rest of the stem.

A closer picture or one of higher resolution might be the ticket here, unless someone on the forum has gone down this exact same path recently!

The only "disease" I'm aware of that affects tomatoes to any great extend is Tobacco Mosaic Virus and I believe it affects the leaves. I could be wrong about that and if so, perhaps the white "mottling" of the stem is some sort of viral infection. If it's only on one stem, I'd toss it into the mulch bin and concentrate on the remaining plants.

All of my plants have it, so it must be something consistent.

mattpayne11 wrote:
All of my plants have it . .

My first reaction was that it could be a calcium deposit (scale), but I couldn't be certain. Now that I know that ALL your plants have it . . I think that maybe a possibility.

Assuming it is calcium, is this something to be alarmed by? Plants seem to be very healthy otherwise.

I've noticed this "scaling" on a number of drip systems, but I've never seen any bad effects.
So . . . just watch it.

All my tomato plants look that way (or worse) at the bottom. I've always assumed the white was where nutrient liquid evaporated and left a salt residue. believe me, the base of your plants look 1000 times better than mine.

Excellent. =) Thank you all.

I took this just to show you what I'm talking about

in case the image disappears

Also a quick glimpse at what may be becoming my new favorite media. . . Marbles!

in case the image disappears

Notice the lack of white around the marbles. I propose that's because marbles are smooth and thus less inclined to wick water up to the surface where the water would evaporate and leave a white residue. Just an idea, ya know.

I'm afraid I disagree with pretty much everyone. I would say its fungal (sclerotinia maybe), caused by too much moisture and not enough ventilation (and of course spores). The thinner diameter is indicative of the cell walls breaking. Is it harder there than in the green areas? Woody, I mean? As the plant grows the stem will get thicker. It looks to me that the plant persevered over the sclero rot. It's unbelievably common in greenhouses and it's commonly overcome. No chemical treatment will stop an established infestation as far as I know. Rockwool is good for sclero and pythium. It maintains a constant humidity around the base. Using perlite and coco seems to work better for me.

Sclerotinia can cause the stem to become woody and thus reduce water flow. This can reduce yields or even lead to further complications down the road. Obviously reduced water intake is going to cause problems. I had a few plants that suffered this when young, but they pulled out of it. But, they produced less and smaller fruit. Still enough for us, so it wasn't a big deal. The stems stayed thinner at the base and I'm guessing the bottle neck is what caused the reduced yield. Those plants were in rockwool. In fact, I have a bunch of rockwool starter cubes here if anyone lives near New Whiteland, IN. I won't use them because of this problem and the higher rate of damping off. There are cheaper, superior alternatives. If I were you, I would keep these plants going, but consider an alternative method later to see the difference.

If it weren't for the thin section, I would then have also said it was salt buildup. I get that a lot, but not with the thinning, scabbing issue.

Thanks joe.jr317
That makes sense to me. Live and learn.

I think joe.jr is right on this.

In many cases this kind of thing isn't really a problem, but it's not entirely harmless either.

Do you think that improving air circulation would help with that? A stronger breeze at the crown would combat excessive moisture, wouldn't it?

I'm sure it can be done. I only have one indoor environment to use for experience and I must admit it has less than ideal circulation. I have a fan that I run on low to medium depending on the humidity of the room. I haven't sunk much money into my grow area because I'm saving for a greenhouse (and drooling because I should be able to get it next year!).

I think anyone who's into hydroponics would love to have a greenhouse at some point. My ideal would be one that's built onto the actual house like an enclosed porch or solarium.

And as long as you're not getting wind burn from your fans, you can't really turn them up too high.

All my plants developed this white stuff I think it's a fungus but cannot understand how they all got it. The soils are not the same???? Leaves are dropping and drying up, I am taking ll the fruit off and throwing away the soil.

Your tomato plants look just like papaver somniferum plants.