Interesting story, thanks for sharing it. I love to read old gardening books and I've read about Vapam, always wondered wistfully how well it really worked. Are you able to plant tomatoes in the same place repeatedly with the Vapam? Do you just treat once a season -- before you plant the tomatoes?
I try to be green and organic and poison-free, but sometimes I wonder what's the point when you learn things like plastic water bottles can cause cancer. I've completely moved my garden this year so I'm hoping for stellar results. Everything - not just tomatoes - was declining in the old garden. And yes, I put in lots of organic material and would solarize every summer for at least two months. I always grow tomatoes in pots with fresh store-bought (expensive) good potting soil. Oh well, wish they'd invent a new "green" kind of Vapam.

Though it is short lived in the soil, it sounds like some pretty nasty stuff(for me anyway). Seems like it is still available at least for commercial growers.

When you Google methylisothiocyanate, you get a bunch of results. This website lists manufacturers of it.

Interesting couple of tidbits on Wikipedia about it.
"MITC forms naturally upon the enzymatic degradation of glucocapparin, a modified sugar found in capers."

"MITC is a building block for the synthesis of 1,3,4-thiadiazoles, which are heterocyclic compounds used as herbicides. Commercial products include "Spike", "Ustilan," and "Erbotan." Well known pharmaceuticals prepared using MITC include Zantac and Tagamet."

Wonder if you feed the plants antacids.............

I think most of the laws about pesticides were made to protect stupid people from themselves. Diazinon was also taken off the market because of people using it in their houses, in fact, spraying it on their carpets to kill fleas. Dursban was taken off because of people putting it in their dog pens, although it CLEARLY said not to use anywhere pets might get it on their feet for a certain number of days.

Luckily, not much can be poisoned with Sevin, but somebody will find a way to get that taken off too.

And what's this I hear about some pesticide used in orchards now being blamed for the bee problems? I keep wanting to say Image?

Idiots kill good things for the rest of us.

That was really more than I wanted to know about Vapam. I do
not beleive even the commercial guys use a fumigant anymore
they just use root knot resistant varities and that is why
in Fla at least the store bought and even the road side
stand tomatoes are virtually tasteless. I consider myself a
kinda enviro friendly guy and I just use the Vapam once a year and it is in the same spot. It kills everything in the soil but I do introduce my own cured compost after the fumigant has evaporated. This year I am trying some seeds
from Peru' S.America. My wife is from there and her sister
says that my new seeds come from and old woman that says they have been passed down from her family for several generations.This is GREAT. It took alot of years to get some
response from the relatives. They do not speak Spanish they speak Quechuea which is the language of the Andes Mtns. of
Peru',Bolivia and Ecuador plus many more dialects. Whew !
Growing stuff is so much fun. If my new seeds planted in
my newly sterlized soil with Vapam are a success I think I
shall name them "BLOOD OF THE INCA" :)

From the link posted below :

" No single, equivalent replacement (chemical or nonchemical) currently exists which exactly matches the broadspectrum efficacy of methyl bromide.

Nematode control measures can be divided into 2 major categories including cultural and chemical control measures. None of these measures should be relied upon exclusively for nematode management. Rather, when practical , each management procedure should be considered for use . "

Read this link for a ton of info .

Here is a link that might be useful: Nematode Management in Tomatoes