Phytophthora and Pythium species associated with root rot of young apple trees and their control

Abstract

Six species of Phytophthora, two species of Pythium and five species of Fusarium were tested for pathogenicity to McIntosh apple seedlings under greenhouse conditions. Phytophthora cactorum. P. cambivora and Pythium ultimum were pathogenic, causing root rot of McIntosh apple seedlings grown in artificially-infested potting soil in greenhouse tests. Captafol inhibited the growth of most of the species of Phytophthora, Pythium and Fusarium examined in laboratory tests. Metalaxyl inhibited the growth of species of Phytophthora and Pythium but not of species of Fusarium, whereas fosetyl-Al was effective in inhibiting the growth of the three genera tested. Metalaxyl was fungicidal to Pythium ultimum and fungistatic to P. cactorum and P. cambivora, whereas fosetyl-Al was fungicidal to all Phytophthora species and fungistatic to Pythium ultimum. Enterobacter aerogenes was fungicidal to P. cactorum and fungistatic to P. cambivora and Pythium ultimum. Metalaxyl alone or in combination with thiabendazole, as well as E. aerogenes alone controlled root rot on McIntosh apple seedlings caused by P. cactorum, P. cambivora and Pythium ultimum under greenhouse conditions.