When visiting vineyards, no matter where in the world, you will here and there come across rose bushes growing at the end of the rows of vines. When you ask why that is, the answers will vary. Some will say it is to prevent disease, while some will say that it is an early warning system to reveal diseases.
Well, those answers are almost true. Back in the days, before we had modern science, rose bushes were in fact a good early warning system against mildew on vines. The same weather conditions that encourage mildew on vines, also encourages mildew on roses. Being different species of mildew though, the risk of cross contamination was non-existent. Furthermore, roses tended to be more sensitive and would show signs of the mildew up to two weeks before it would affect the vines, giving the farmers ample time to put in counter actions against the mildew.
Unfortunately, years of clonal selection, crossbreeding and so on, have made todays roses far stronger. Meaning that the risk of mildew, black-spot and other diseases is more or less eradicated, leaving the rose bushes at the end of the vine rows completely inefficient, even if they are still very decorative.