I would hate to steer you wrong, but I have never heard this, experienced
it, read it any literature, nor heard it related in any of the vineyard
management classes i've attended over the years.

In my experiene, the bigger issues;
1. Removing previous vines. Vines develope very deep, strong root systems.
After even a few years, getting the roots out is all but impossible. I
pulles some self-rooted 3 year old Syrah a couple years beack. and we had to
work terribly hard to get them out.
2. If the ivnes are 5 or more years old, might you consider grating rather
than pulling and replacing? Given the years before you get significant
production, this might be a more effective strategy. As I said above, I
pulled and replanted some Syrah a couple years back. I replanted with
Cabernet Sauvignon. I would like to move some more Syrah to CS next year -
but am planning on grafting so that I don;t lose 3 years of production.

Good luck!

R

>I am thinking of pulling some Chambourcin and planting Cabernet Sauvignon
>in their place. Someone said that unless you get all the roots, the
>remaining roots, as they die, will secrete a substance that is toxic to the
>new plants. Anyone have any experience in this?
>