Fungal infections of grapevine roots in phylloxera-infested vineyards

J Granett, A Ümer, P Pessereau, M Walker
1998 Vitis   unpublished
S u m m a r y : Wounds caused by feeding of grape phylloxera on grape roots can become infected with a variety offungi. Fusarium roseum, F. oxysporum and Pythium ultimum are important in Vitis vinifora Chardonnay wounds whereas F oxysporum and Cephalosporium sp. are important for the moderately tolerant rootstock AXR#l. Proportion of root lengths infected in the phloem parenchyma were measured in two vineyards through the 1996 growing season and into the winter. lnfection rates were
more » ... es were highestinspring (as measured in May) but decreased to a low Ievel by the end of summer. There was a second infection peak in fall. We suggest that the decline in fungal infections was due to death ofhighly infected roots and their removal from the sampled pool ofroots. Loss ofroots is a logical cause of vine decline and explains why there have been poor correlations between phylloxera populations and vine darnage syrnptoms. K e y w o r d s :