My little elm is attacked again by red spider mite. I already misted my bonsai whit some kind of solution but it seems that it doesn't kill the spiders, i washed the lives with warm water (i searched on the net and i found that this spider hates water and humidity).I will try with other solutions if the water doesn't work.
You are correct and it is less likely that an infection will occur if plants are frequently misted and grown in a humid atmosphere - but this is not always convenient. Apart from using a proprietary brand of chemical or importing biological control I think you are doing all you can by spraying and gently wiping the underside of the leaves.
It will take time but if you persevere I think you will succeed. You need to be sure that you are dealing with all plants in the vicinity that might be infected and not just those that are evidently so.