panhead is correct about air flow. I have heard this from another grower from the San Diego area, they got a bad mite problem there I hear. Get a green bamboo shoot and stand it up next to your plant so it is touching the leaves. Put a fan directly on the plant so it is moving around all the leaves. The spidermites should go to the bamboo since it is sturdy, just wipe them off.
Whats amazing to me is that spidermites cause so much devastation in such a short time yet the bugs are sooooo easy to eleminate from all grows using all natural methods,all natural methods that work 1,0000 times better than any chemical or lady bug.
Growers are plagued by these pests & try all kinds of bombs,sprays,traps,lady bugs ect yet the one method assured to stop them cold they act as if you never even told them about it & keep searching for another method.
The answer is right before everybodys eyes,as with any animal or insect they all require a fairly specific habitat,animals & insects around the world are becomming extinct because of loss of habitat.
Animals & insects can overcome predators,they can overcome poisons & pesticicides by building up a tolerance,the one thing no animal or insect can overcome is loss of habitat,the habitat becomes even more linked to the insects survival when there is a weather condition which its impossible for them to adapt to.
Spidermites need a steady climate to thrive in,they seek out conditions of stale non moving air currents,the less air current the more they thrive,spidermites need the underside of the leaves to be a non moving enviroment to thrive.
When the enviroment is not suitable for a random spidermite to thrive in it cant breed,if it can breed it dies off.
All that has to be done in any grow is to seperate the plants far enough where fresh moving air currents can flow over every leaf surface,if this is accomplished then the random spidermites we bring into our grows on our clothing or infected clones & mothers will never gain a foothold & establish a colony or group & the room will never be infested with mites.
For rooms that are allready infested heavily its still the same philosophy used to rid the room of them,take away their specific habit,seperate plants so all leaves can flutter at medium rate,place a sacrificial plant in the room that is not being affected by wind,with the calm conditions its natural for the mites to relenquish their foothold on the affected plants & move to a more suitable location,which just so happens to be the sacrificial plants in the room.
Take the sacrificial plants outside after carefully covering them with a garbage bag,once outside spray the hell out of the plant with RAID bug killer & replace with a fresh plant,repeat several times until all mites are gone.
Once the room is mite free just be sure to keep lots of fresh air moving thru the canopy & lower areas of the plants,in thick dense grows such as most hydroponic grows air penetration can be accomplished using a 4 inch centrifugal fan,or squirell cage fan.
Take 4 inch wide pvc plumbing pipe & drill holes in a straight line about 1 inch apart,lay 2 or 3 of the pipes long way across the table with all holes facing upwards,now connect all the pipes together using 45 degree elbows on one end,the other end leave the center pipe open & connect the pipe to the output side of the centrifugal fan.
This takes up zero grow space & gives a steady flowing never ending air current applied directly at the main areas where spidermites live,under the leaf.
Spidermies arent shit to eleminate permanently if you use the approach of destroying their habitat.