Bugs on Vanda roots

[craigherb]

I have a couple of mature Vanda's that are in small baskets supported over vases with gravel in.

I've noticed recently lots of pin head sized dark brown/black, hard shelled bugs that seem to feed on or draw moisture from the roots of the plants. Never seen them on the foliage.

I mist once or twice a day with rain water. I have used Provado ultimate bug killer aerosol into the vase once, it clears most of them but they have multiplied again.
Theres no webbing so don't think it's red spider mite.

Would anyone know what they could be?
Would it be safe for the roots to use Prov UBK that you mix with water, to drench the roots properly instead?

Don't want to damage the plants but would like to clear them before they harm the plants.

Any ideas or advice gratefully received

Craig