Phylloxera

[Kcwhippet]

Soil type plays a role also. The vines planted in the delta region of Contra Costa county are in sandy soil and that is an inhospitable environment for the nasty little buggers. So, you'll find the Zins, Mourvedres and others, mostly from Cline and Rosenblum, are from self rooted vines. From all the replanting the Napa Valley wineries have had to do as a result of using the recommended rootstock, it looks like some of the folks from UC Davis aren't as infallible as once believed.