Does anybody knows of a systematic monitoring methodology which is indipendet on the skill and the eyes of the observer i.e. any one that monitors will end with same result
I am not familiar with agro and bio-tech, but if you could resolve and identify a unique chemical composition/spectroscopy signature of the mites, then you might be able to devise a detector to detect it, and then apply to statistically powerful number of some random sample of plants.
As I said, this is outside my field, but it can maybe get your problem solving creativity flowing!
I hope you would find a solution using organic permaculture, so I would also suggest to see if you can find any organic farmers of citrus and see how they are managing the problem. :)