I've kept a garden since I was a kid.
The very best way to
ruin cucumber plants (among others) is to chew snuff and spit it in the garden. Tobacco Mosaic Virus can be (and in my case, usually is) transmitted laterally and screw up everything.
For that same reason, I never touch plants if I've dipped snuff or smoked a cigar, and I don't smoke while I'm working in the garden.
I wouldn't sweat it if it weren't for the fact that I couldn't grow cucumbers to save my ass until I identified the disease and figured out how I was getting it in my garden.
So far as tobacco ashes go,
I wouldn't even consider putting them near my garden.
If the ash weren't to
touch anything else and were kept out of the ashtray so they couldn't get flecks of tobacco mixed in, I still wouldn't do it.
It's just not worth the risk.
Since identifying the problem I mentioned, and correcting my habits, I'm a
world class cucumber grower. I have
rafts of cucumbers before anyone in the area, and they're perfect and gorgeous.
Here's a link to
TMV.
Hope this helps!!!
Scott