Too true about nipping the diseases before they spread. There is a daily cycle apparently and iirc common to release spores in the evening when temperature drops, but it may be different depending on the organism
yup I have forgotten whatever I read, I know I was doing the rounds to remove and bag every bit of mildew before sundown at one point. But I think late blight was different and spored in the early afternoon... suffice to say they have a built in plan for getting the spores out there.
One thing about grey mold, which we also get here with a vengeance, is that the spent blossoms or flowers that drop are patient zero for the mold. I have found a few varieties less prone to that but in general the floral parts of tomato produce substances which are the ideal substrate for the mold. As soon as they drop unseen onto a leaf or worse yet, a stem, there it spreads and grows.
So a key part of sanitation routine for us is to shake off or pick off and dispose those petal or flower drops whenever doing the pruning and tying. If that is done on a regular basis, mold is much less of a risk. The year I looked after the tomatoes at my friend's farm, I found that once a week was just right for those pruning jobs, and kept them pretty much mold free.
Some varieties are extra susceptible to mold or other diseases though - I honestly have culled quite a few from my 'want to grow again' list if I find they are high maintenance.
