Strange brown & black dots on petioles! Please help!

[Benhamish]

Hi, we have a number of plants growing outdoors (different strains). Recently some of them have begun developing these dots on their petioles and moving into the leaf. I have attached some pictures. I haven't seen something like this before. We do not know if it is natural, a fungus, or a virus. The dots are confined to the upper epidermal layer of the petiole. If anyone know what this is please post. Thank you

I also want to mention that we recently changed nutrient regime.

These are links to pictures, I don't think I can post pictures yet, they are 1mb

https://pageturner.biz/demos/public_assets/images/petioledots2.JPG
https://pageturner.biz/demos/public_assets/images/petioledots.JPG

 

[Koren55]

Are the dots moving? If moving they could be some sort of mite.

Are they completely flat? If not, if they're a stationary bump, they could be a type of scale (an insect pest).

If they don't appear to be mites or scale, you could be seeing the petiole's stoma. Plants use stoma to breath carbon dioxide and to transpire water. If you're using new nutrients, they could be getting deposited in the stoma as water evaporates. Are the black dots appearing underneath any of the leaves? Each leaf has stoma, especially on its underside.

What's the composition of your new nutrient mix? Perhaps you're adding too much of one mineral, so much that your plant is trying to get rid of the excess - thereby darkening its stoma.

Try the flushing process, adding plain water to its roots, over a few days. The plain water will help flush out the excess minerals the plant didn't need.

Note: Do further research before trying my suggestion. Anything I suggest is based on my past experience and training as a Botanist. But since I cannot see your plants first hand, it's only a guess; if you follow my advice you do it with that understanding, that if something goes wrong, it was your choice, and I in no way can be blamed. Koren

 

[Benhamish]

I will try flushing some with water. I looked at some scale pictures and the dots seem similar to very small scale. I am also going to try and look at some through a microscope. They are mostly confined to the topside of the petiole, the leaves have their stomata on the underside, is this true of the petiole as well?

 

[Benhamish]

Hello, I looked at these dots at 100X magnification. They appear to be some type of mite or armored scale. I am attaching pictures.

This is a picture of a leaf, we noticed little black dots on the upperside of leaves and trails,

This is 100X of the dot on the leaf,

and this is 100x the dot on the petiole, are they eggs or something?

Do i need to go to higher magnification?

 

[AnimaSola]

Leaf miners leave the trails, not sure about the spots. It actually looks more like thrip or spider mite damage.

 

[Koren55]

Wow, interesting photos.

As for petioles having stoma, they're really present all over. On leaves they're on both sides too, but mostly on the underside.

Your one photo of the leaves sort of show that it's above the surface. In that case it could be a type of scale. Can you remove one? I know it will be difficult, but to prove its scale you need to look at its underside.

Have you tried to use a fish oil based insecticide? There's one I use that works as a fungicide, insecticide, and miticide. I'll get you the name tomorrow.

Just be careful of what you use. Only use organic type controls.

You can always get some chives. For my two plants, I placed a lot of chives under each one near the stem. Before I added them my plants had red spider mites. I sprayed once with the fish oil, then added the chives. Since then, no mites.

 

[Suntana]

Looks like thrip shit to me.