Wow - this is an eye opener for someone in CA! We have so many vineyards in this state, and they are spreading wildly. However, I have never heard of this problem (probably because the wine, grape, & raisin industries are so strong that they prevent it from happening).

It has happened in my garden, however. Luckily my next door neighbor who hired "gardeners" who mowed & blew & sprayed herbicide everywhere decided he could no longer afford them because of the recession - yay!

Jackie