A winemaker in Languedoc, Jeff Coutelou at Mas Coutelou, has his own recipe to avoid diseases in the vineyard. He has a lot of different varieties planted in the same vineyard. It protects the vines from viruses, he says, and makes them less susceptible to other diseases.
Read about Jeff Coutelou on Drinks Business.
In the past, wine producers often had many grape varieties planted in the same vineyard (“en foule” (**) it is called in French). Now this is considered as inconvenient but who knows, old habits may return.
(**) Update: We have picked up the term “en foule” from vine growers we have met that have applied it to vineyards planted with different grape varieties mixed together in one vineyard. It seems that a more correct application of that word is to designate a vineyard that is planted, normally with a single variety, without trellising on wires and where the propagation is done by rooting branches. The vineyard thus becomes “disorganised” like a “crowd” after some time. This is also a method that is not much in use any longer.