What they look like
Size
about 0.02 inch (0.4 mm), usually needing a magnifier to see clearly
Body
four pairs of legs, one body segment, colors from red and brown to yellow or green
Home
mostly undersides of leaves, also around buds, moving on silvery webbing
Damage
tiny brown punctures with a yellow ring where they pierce and suck sap
Why they explode indoors
Ratio: new hatches run about three females to one male, and a female can lay up to 200 eggs.
Speed: the cycle can repeat about every eight days in a warm, dry grow room.
Webbing: as numbers rise they bridge branches and plants, and they can carry disease.
Mothers: infected stock sends mites to every clone cut from it.
Keep them out
Quarantine
isolate every new plant before it enters a clean room
Air
run a fine dust filter on intake so mites are not blown in
Clothes
do not walk in wearing gear that was just outdoors or in another garden
Scout
act at the first webbing or yellow-brown stipple, especially in a mother room
Slow and reduce a population
Humidity
Aromamites like dry air
Soap
Aromainsecticidal soap smothers many mites but rarely wipes the colony, even twice a week
Pyrethrum
Aromaworks on some populations
Oils
Predators
Aromarelease predator mites at the first sign