The White stuff is named “bloom” and it’s really generally engineered into the rubber to guard the rubber from dry rot. Dry rot is basically simply injury brought on by ozone, UV, Cosmic ray and whatnot. Dry rot makes the rubber craze, flip brittle, crack and shrink. It could additionally simply be poor rubber formulation the place some part has reached its solubility restrict.
You possibly can clear it off with any good detergent cleanser, however it should ultimately come again. When you use the controller with any regularity, it should naturally rub off and you’ll not even discover. Nevertheless, in case you retailer the controller for some time it could construct up once more to seen ranges.