What do they look like under magnification?

Dan

Hi Mariann,

I'm experiencing the same thing with my spinach . . . not lettuce though. We've been washing it away and eating it. I hope it isn't harmful :(

I've never looked at it under magnification. It doesn't seem buglike (aphids, etc.).

OP said " I let it progress on a few spinach that I did not harvest, and I started seeing small `lesions` when I rubbed off the dots"

Well that's a helpful bit of info.

Look up white rust.

That's not what white rust looks like, nor how the OP's described indications manifest themselves in white rust. There needs to be a better picture or description of view under magnification.

Dan

Yes, I know.
But based on a very small image, plus a sketchy description, that's my guess. What's yours?

To me it seems like hardened 'honeydew' from aphids from the description, so that's the best I can do. Confounding distance diagnosis, surely, without magnification.

Dan

What about exudates from stomata? Maybe oxalate exudates or salts. Most plant pores are on the underside of the foliage.

How's THAT for a guess, Jean? lol

I like that WAG better than mine. But mine was first. ;o) Whan I get that on my tomatillos I know the aphids & other sucking insects have visited.

Dan

Thanks for the comments from everybody. First of all it is surely not hardened honeydew. I have not seen a single aphid on my plants so far. They have been covered with a floating cover and few insects got under (flea beetles mostly) but not aphids. I checked out pics of white rust and my plants do not look like that at all. I like the exudate from stomata idea though. The symmetrical arrangement of the dots seem to confirm that.
Now I am wondering why other plants would not show the same. I started seeing some on my lettuces but it never got as bad as on the spinach and it was on the upper sides of the leaves where I watered them. So it may be only due to the hard water we have around here???
Eventually, the salt does not do good the plants....at least that is my experience.

Mariann

Yes, I think rhizo gets the golf clap.

Thinking out loud here, I wonder if it is like guttation moisture and the sugars are the residue after evaporation of moisture overnight. That is: the roots are pumping for 45 leaves, and only 10 are evapotranspiring, so more moisture and pressure going thru than needed and the stomata 'leak' under the pressure. The sugars for a couple days could be attracting fungi, bacteria causing the deterioration of the tissue.

I can't find this phenomenon in any of my pathology texts, so just thinking about it from another angle...

Dan

So, if it's guttation, what about the "lesions" you saw develop if the spots were left as is? Perhaps a different problem?

I am having the same problem with my spinach. I looked at the dots under 200x magnification and they are perfect little spheres. I have noticed that the dots do tend to follow the veins and are primarily on the underside of new leaves. To me it looks like sugar. I will try to post pictures later.

Guttation, as has been said.

I know this thread was from last year, but I was wondering if anyone has come up with an answer. I have the exact same thing on the underside of my spinach leaves this season.

gumshoe- seems like you have a microscope from your post- to actually see the stomata under magnification you can paint 2 thin layers of clear nail polish (let dry between coats) on the under side of the leaf, then use clear tape to pull off the nail polish- this makes a nail polish cast of the stomata that you can then put on a slide. Stomata look like donuts or flat tires under magnification.

Hi,
I am going to tentatively confirm that the white dots are residue left by aphids. I have had this problem on my (unheated) greenhouse spinach all winter and I couldn't figure out what it was. At first, I assumed these were some kind of egg, since they are appear to be tiny spheres when viewed under a magnifying glass.
Now, having read this and other threads and carefully observing the plants for months, I am deducing that it is the aphid residue.
For a while, I didn't think I had aphids but just yesterday I noticed clusters of them way at the base of the plant.

the curious thing is that the small white dots do not appear on the neighboring arugula and parsley plants, nor the collard greens or the rosemary, only on the spinach... Not sure why that would be.

I was thinking the same thing. My spinach is covered in these perfect tiny white dots underneath. not my lettuce, not my basil, just my spinach. I finally saw a few aphids at the very base of a couple plants. I hate them :( Anyone know if it is safe to eat if I wash off the spinach?

Ditto for me, and that picture was spot on (not sure what anyone was complaing about).
Same tiny white dots on the underside of the leaves only. No aphids to find. And lettuce completely spared. But... I'm on the other side of the globe in Australia.
Not convinced or reassured by guttation, as it's clearly not water. Whilst we wait for a convincing answer my spinach has been pulled out and will not be gracing my compost pile. There's plenty of other greens to enjoy.

Mariann_gardener,

What did these spots turn out to be?? I have the exact same things over ALL my overwintered spinach. I don't want to rip them out but I don't want bugs either. HELP

The answer hasn't changed since this thread was first posted three years ago. These little crystals are the result of calcium oxalate and other naturally occurring chemical compounds in the spinach. Most of the stomata (pores) are located on the underside of plants....when the plants respire and transpire, water vapor exits from those pores. The salt/sugar -like crystals form when those exudates evaporate around the stomata.

The hard little deposits fall to the ground as they dislodge. The spinach continues to produce the chemicals, which continue to collect on the outside of the stomata, which will continue to evaporate....forming more and more "dots ".

Spinach, by the way, produces a lot more calcium oxalate than most other plants.

Edited to remove double post.

This post was edited by rhizo_1 on Mon, Mar 18, 13 at 6:14

I looked at it with a microscope. What I see is what looks like a small sphere connected to a tube coming out of the leaf in some spots. In other places I see little crystals, which I'm guessing is what remains after the little sphere's pop or collapse. There seems to be information about this at the link I'll provide.

Here is a link that might be useful: Spinach: the gritty truth

Thanks for the info from rhizo, and the link from tim. This put my mind at ease, as I've been having the same issue with my spinach.

Thanks for this

I had same issue which I have concluded to be oxalate crystals

http://www.helpinggardenersgrow.com/2013/01/spinach-gritty-truth.html

This is my lady's finger plant.It appears to have small crystal bubbles forming on it.I don't know what it is?Is it dangerous?

suhayla, okra (lady's finger plant) is another plant that produces high levels of calcium oxalate. Please read the old information in this thread to learn about it and you'll understand that it's perfectly normal and nothing to worry about.

Thank you

From unh.edu website:

These are not spores, insects, or eggs, as many people believe. They are trichomes. Trichomes are hair-like outgrowths from the epidermis of the leaf, and many plants (including spinach) produce them. Trichomes come in all sorts of shapes and sizes, and have different purposes. In the case of spinach, if you look closely with a microscope, you can see that there is a little hair that comes from the leaf surface, and a big glob at the end.

https://extension.unh.edu/blog/what-are-these-little-white-spheres-spinach-leaves#:~:text=These%20are%20not%20spores%2C%20insects,(including%20spinach)%20produce%20them.

Noone freak out. They are trichomes - spinach hairs and yes they have a glob on the end under magnification