Nematodes are almost always invisible. I doubt you have nematode damage. They live in the soil after introduced and are a beneficial introduction.
Discussion
Wrong word but talking about those little guys you can see crawling on the stem.
Spider mites?
Just regular decomposers
Gotcha. Its hard to tell what I am looking at on the stem. Without a microscope picture I just don't know.
You can use a cotton ball soaked in rubbing alcohol and use that on your stalks. That will kill what you have going on there on contact and not harm your stalks. Nematodes watered into your soil 1 x per week for 3 weeks in a row will boost your beneficials while feeding on bad microorganisms and get rid of these things on your stalks that are likely living in the soil.
https://www.naturesgoodguys.com/collections/beneficial-nematodes
They go away completely if i just dont water on the stalks
I use triple threat predator spider mites. You can order them from Natures Wonders (see below). You need to apply before flowering otherwise you will get the holding substrate (grinded corn husks I believe) on the flowers and you can’t get it off. Best if used on clones and in early veg. This way you get control early on but also it takes a lot less containers to sprinkle on because your total square footage is much less. I use 3 times, 5 days apart. That way you cover the full life spectrum of the mites you are trying to get rid of. If you are already in flower you can use Neem oil up to 10 days before harvest to maintain control. See link below for Einstein Neem Oil product. Since you’re indoors, always apply the Neem oil about an hour after lights go off.
This is the best Neem oil you can get:
Nice i used beneficial insects for thrips and it really fixed things up
I dont have any spider mites tho