Man, I kinda wish I got to this thread sooner.
I feel bad for ya, there was a lot of bad information brought forward.
My experience with broad and russet mites is extensive and I have done enough research on them for a lifetime.
First off. The photo that I quoted above, are NOT russet mites.
Hemp russet mites appear like microscopic maggots, as shown.
View attachment 847702
They are absolutely vile creatures. The damage is very obvious and specific if you know what you are looking for. They eat the freshest youngest most vigorous growth from the growing tips, and absolutely swarm pistils. They are so small and reproduce so quickly that (get ready for this) the areas they are concentrated turn yellow and sticky, as shown. The yellow is a pile of russet mites hundreds of thousands high. Absolutely disgusting and at this point, beating russets in a large scale grow is nearly impossible without losses.
View attachment 847705
View attachment 847704
Now, as for the suggestion of using neem to combat the broad mites you may or may not have.
Unfortunately I will strongly disagree with that one. Broad mites (as well as hemp russet mites, and cyclamen mites) find neem relatively benign. You may knock down populations slightly.
However, along with
pyrethrins, without having a translaminar effect (able to travel through the leaf tissue, not to be confused with systemic) they are simply not effective against broads/HRM/cylamen. These mites are simply too small, and repeatedly hitting the colony with a mild pesticide which only kills a small portion of the adults, and NONE of the eggs, is FAR from ideal.
[
https://www.ncbi.nlm.nih.gov/pubmed/26084090]
And unfortunately, as you have already sprayed neem, you will not be able to spray micronized sulfur, which has been recognized by many (large body of anecdotal references) to be THE treatment for broad/HRM. In the future, I recommend Safer brand wettable sulfur, 2tbsp/gal sprayed weekly for IPM, or every other day for 2 weeks if an outbreak occurs.
In a commercial setting where it is impossible to simply eliminate all biomatter and sanitize, I highly recommend doing a short rotation of spiromesifen (
Forbid 4F) and abamectin (
Avid) before starting sulfur, on vegetative plants only.
As for the predator mites, they lose effectiveness as soon as the resin begins to build. Around week 4 they are no longer financially viable.
A much better option for broad/russet mite treatment in flower is Nuke Em and
Green Cleaner, rotated, being sprayed every other day to catch subsequent egg hatchings.
Anyways, onto your situation. I wouldn't rule out broad mites yet. You've come forward with some pretty classical signs of broad mites. I would keep scoping, primarily your tops. Can we see some close up photos of your tops? They seem a bit yellow. Also, do you spray your
neem oil while the lights are on?
If you've got mites, your pistils will be constantly being eaten, and your new growth will be deformed.
Another observation I'm going to make is that all of your tops generally seem lighter, with purple stems. Have you checked your runoff to ensure that
A) you are not underfeeding
B) your plants are not locked out from the pH being off, or salt build up?