That can be a sign of the fuel not burning properly. I don’t want to say not burning because that is usually black smoke.
You may have an injector that is not spraying correctly. I noticed my 7040 doing it last year and the weather was rather cold when it happened. The fuel will not burn properly in an engine that is not hot enough. With mine, I just happened to catch it in the sun just right to see a grey haze as the engine came under heavy load. I needed to fuel up so fueled and I added some Power Service and went back to work. Within a couple of hours, the white.grey haze was gone. So, was the original fuel the problem or a sticky injector the culprit. Whatever it was, it has gone away.
Also, I keep an eye on the oil level to make sure I wasn’t gaining or losing oil. Also, the white haze smelled like diesel, not burned oil. If an injector had some buildup on it and had a bad spray pattern, that was probably the culprit.
Finally, as it gets cooler, if you make sure you warm up at increased throttle and increase the throttle if you leave the tractor. if not, you can get carbon buildup and cylinder wash down due to low engine temps.