Relationship between plant growth stage and disease severity in stem and root rot of hydrangeas

Abstract

In this study, we examined the relationships between plant growth stage and disease severity in hydrangeas infected with stem and root rot. Hydrangeas were inoculated with four oomycete pathogens (Pythium myriotylum, Globisporangium splendens, Globisporangium spinosum, and Globisporangium sp.) at 0, 1, 2, 3, and 4 months post-transplantation. Plants inoculated with all four pathogens showed disease symptoms until at least 1 month after transplanting; however, the damage caused to plants was found to become less severe with a lengthening of the post-transplantation period prior to pathogen inoculation. Only one of the four oomycete pathogens (Globisporangium sp.) caused significant damage to hydrangeas when inoculated at 4 months after transplanting.