I've picked some in "commercial orchards" but have never been asked or required to consider orchard sanitation while picking. Most trees are of the same variety, and susceptibility, and I'd suspect - either infected or not... Our local grape vineyards are quite the opposite: most require stepping into a bleach-tray before interring the vineyard! Regarding the tree-fruit growers: perhaps they figure the amount of "spraying" they do will control the spread of virus & bacterial agents. I always notice a coating of "white powder" spray residue on the stems, fruit, and leaves in such an orchard.
(Q a) Smart people do it! Once, while grafting at our Spring Event, someone "half-jokingly" suggested we call it the, "HOS virus exchange" - vs. scion exchange
~ I had my spay-bottle of alcohol, and my neighbor had his trusty can of Lysol
(Disinfectant); but the "joke" had validity. I doubt most people sterilize their equipment between pruning or harvesting. Pruning remains my fear of spreading disease; but to sanitize saws (& chainsaw), hand pruners and loppers between each tree is beyond my level of commitment. But with an orchard full of Arial Crown-gall, Anthracnose, and everything in-between - maybe I should have?
Having given this thought, I'd concluded years ago that a Sapsucker (live-wood-pecking bird) moving from tree to tree, or any insect puncturing a leaf, then moving to another tree could spread most anything. When I prune I do make an effort to "alternate species" - pruning an apple tree, then a fig, then an apple, then a persimmon, then onto a pear... I figure the sawing and slicing will "rub clean" the tools, and notice most of these diseases are species specific.
(Q b) As mentioned, I've used a plastic spray bottle of alcohol to sanitize my pruners between grafts. That neighboring grafter said his large aerosol can of Lysol
should last for years! He gives a small spray & wipe between his work as well. But my plastic
spray bottle seems to have "melted" internally from the alcohol - so I best be shopping for some Lysol!
As always; I'd be happy to hear the techniques of another Orchardist - but without holding my breath - I thought I'd best give you my take