DECLINE SYMPTOMS ON ROOTS OF QUERCUS-ROBUR

A comparative study by light and scanning-electron microscopy of fine and coarse roots from healthy and declining oaks demonstrated a progre ssive deterioration of fine roots and mycorrhizal systems on mature tr ees in decline. Histopathological events such as infection of cortical and vascular root tissues by parasitic fungal hyphae leading to the I mpairment of woody roots are described. Distinct disease documented, s upporting the hypothesis chat Phytophthora spp. are involved in oak de cline.