What Troad is thinking of is fungal leaf disease, which
benefits from a moist environment. Here in N. America,
we are often struggling to keep the leaves dry enough
to inhibit the onset of Early Blight or Late Blight, and
we go to great lengths to avoid splashing spores from
the soil up onto the leaves and stem of the plant.
(That is why you see a lot of mention of Daconil in threads
here and there. It contains an anti-fungal compound that
seals off sites that fungi bind to on a leaf or stem.)
If we spray tomato plants (anti-fungal, pyrethrums,
garlic-and-cayenne, foliar feeding, whatever), it is
done early in the morning on a hot day, so that the plant
dries off quickly, and hopefully not on a windy day.
Brief BER fact sheet:
http://ohioline.osu.edu/hyg-fact/3000/3117.html
(Note that the "inches of water per week" in that page
probably varies in the real world with the exact kind of soil
and weather that you have.)
Some other calcium sources besides lime: gypsum (that
is what drywall is made from; used when you have near
neutral soil already and don't want to shift the pH upward);
crushed (ground if possible) eggshells; chipped oyster shell;
bone meal; fish bone meal; crushed crab shells; synthetic
calcium carbonates like SuperSweet (fast breakdown);
wood ash (fast breakdown, can radically shift pH upward); comfrey leaf; vitamins (this is a fairly expensive calcium
source).