Abstract

Root rots of grapevine in California are caused by several soilborne pathogens. While root rot in vineyards in general has been considered to be a relative minor problem, nearly all root diseases have increased in incidence and severity since the introduction of rootstocks resistant to Phylloxera. Pathogens such as Phytophthora spp. and Armillaria mellea have been known to occur for many years. However, seldom did root rot become a serious problem in vineyards. New diseases such as Petri disease caused by Phaeomoniella chlamydospora, vine decline caused by Phaeoacremonium spp. and black foot caused by Cylindrocarpon destructans have only recently been shown to occur in California. Wilt caused by Verticillium dahliae has become more prevalent in nearly all grape growing regions in California. Though losses due to actual root disease have been minor over the past 10 years, losses due to vineyard reestablishment have been large.