I have also observed these little soil mites, or whatever the hell they are, within the last two months. I was confused because they aren't on the plants, so they can't be spider mites, and there aren't any flying insects present, so they can't be immature gnats or root aphids. They seem to be doing no harm to the plants, and the minor gnat problem I've had for over a year now is gone, leading me to believe these could be some sort of beneficial. During the last few months I've been recycling soil straight from harvested plant containers for vegging plants, so maybe as mentioned in an above post, decomposing roots have attracted them. I currently don't mind their presence, but keep their population in check by using a diluted Dr. Bronners peppermint soap spray on top of my soil weekly. I actually use some preventative methods on the regular to prevent spider mites and other insects from living off of my girls, which is why their presence intrigues me. It seems like a few of you have mite problems, so below I'll post a writeup of the methods which have helped me combat/prevent mites and other pests for just about a year now:
I have had spider mites once out of the blue. I found a boiled down habanero concoction to be extremely effective, cheap, organic, and the plants loved the shit (human lungs, skin, and eyes.... not so much). I made one (1/2 gallon?) pump sprayer of this stuff and applied it on the top and bottom of all leaves, a few days in a row, basically until it was used up, then continued to use plain water for a week or two just to be safe.
However, upon further research I found the key to successfully keeping them out of your garden is interrupting the breeding process, so really it's not about 'what to use' but instead 'frequency of use'. Since then, I spray down all plants every few days (aside from those late in flowering), and have not had mites since. Many overlook the benefits of foliar feeding, so if you're one of those people, this serves a dual purpose.
Here's more or less my routine/spray mixes:
-I usually spray on watering days for convenience.
-I brew an AACT once a week, I'll use some in a hand sprayer and dilute about 50/50 with water (sometimes more/less, doesn't seem to make much of a difference), and foliar feed (again, top and underside of leaves).
-All other non-aact waterings are accompanied by a silica and water (or plain water) spray.
-I spray all solutions pretty liberally, everyone has a different environment so I can't speak for every situation, but I've never observed leaf burn, regardless of time sprayed.
Tips:
-I do this as a personal med/hobbyist grower that can't spend all day in the garden, so if you grab a bunch of cheap hand sprayers from a local home depot, walmart, etc., and premake your solutions (with the exception of AACT and other solutions that won't keep), even the laziest of growers can do this on the reg. Even plain water alone would benefit foliage and prevent insects from inhabiting and breeding on the plants.
-Some of my sativa doms get deficient in Cal/Mag, so I always have an epsom salt/water spray on deck when that deficiency is noticed.
-I personally avoid neem, and that is true with many others around here. Only leaf burn I've ever had came as a result of using neem. In my opinion, it works due to its consistency which causes a stickiness on foliage, preventing insect breeding. I'm sure that film also caused the leaf burn. So basically, neem will work without much effort, but foliage will suffer. If you have the time and wish not to effect foliage, diligently spraying leaves with water daily will do the trick. As previously mentioned, my preference for peace of mind is the habanero which will kill everything on contact, followed by water which will prevent the remaining survivors from breeding.
-I use a very diluted Dr. Bronners Peppermint/Water mix as a soil spray every week or so. I've heard this creates a film on top of the medium which messes with the wings of flying insects, so when they mature and emerge from the soil they can't fly/mate.. But the reason I use this is because peppermint oil is one of the few organic treatments that will kill many types of insects on contact.
-Obviously don't foliar feed nutrients too frequently or they'll certainly burn. I generally spray the tea solution once a week, and plain water or silica water for the rest of the week. This also helps to wash off the residues that will build up from tea and epsom salt sprays.