You have probably been to vineyards in Australia or around the world and wondered; why do so many vineyards plant rose bushes at the end of a row of vines?
No, this isn't a silly question and yes, there is a good reason.
The best analogy for the use of rose bushes is the canary in the mine shaft. When miners travelled below the surface they used to carry a canary, because noxious fumes would kill the canary before the miners and give them warning to get away (which probably provided little solace for the poor canary).
Similarly, vignerons plant a rose bush at the end of the vine row because they are much more susceptible to a range of similar diseases, including mildew & black spot (fungal leaf infections) than grape vines. The presence of sick rose bushes alert viticulturists to spray the vineyard, eliminating the disease before it can affect the vines.
We have much more robust spraying systems in modern viticulture that virtually eliminate the presence of such diseases, but for us (and a vast majority of growers) there is still function to the roses. The rose bush is still a useful indicator to ensure that spraying programs are successful and that the grape vine leaves are healthy overall. Added to this, they are a traditional vineyard feature that encourages a richer vineyard ecosystem by attracting bees and ladybugs, deterring insects and micro organisms potentially harmful to the vine.
So, next time you enter a vineyard remember that every rose has it's thorn.. and practical viticultural purpose.