First record of Phytophthora cinnamomi on cork and holm oaks in France and evidence of pathogenicity

In 1995 and 1996, a survey for the presence of Phytophthora cinnamomi in cork and holm oak sites in southeastern France was carried out. Twenty-four sites were chosen. Tree decline severity and other characteristics were assessed. Subplots of four trees were more fully investigated: relative soil water content was assessed and Phytophthora isolation was attempted from soil samples. When cortical lesions were observed, isolations were carried out from infected tissues. In six cork oak and one holm oak sites, P. cinnamomi was isolated from soil or trunks. All the different isolates obtained in 1995 were aggressive on cork and holm oaks. However, these species were less susceptible than Castanea sativa and more susceptible than Q. rubra. These results confirm the pathogenicity of P. cinnamomi towards Mediterranean oaks and its possible involvement in the decline process of these species.