According to your description of the situation, and picture analysis, most likely is the tea mite, the picture is like "if the mite" damage caused by the problem, the damage is serious can lead to leaf albino drying and shedding, can be used to avidin or carbofuran or thiabendazole or spirodiclofen or butaflumicarb or efenpyroxam or ethacryzole spraying prevention and control, be sure to play evenly and penetrate, you can add the Organic silicon additives spraying effect is good.