Evaluation of Penicillium janthinellum as a Biological Control of Phytophthora Root Rot of Azalea

Abstract

Wheat bran inoculum of Penicillium janthinellum (Biourge) [1% w/w added to pine bark (PB) container medium] suppressed “`root rot of azalea (Rhododendron obtusum Planch.) caused by Phytophthora cinnamomi Rands in greenhouse experiments. Shoot fresh weight was increased by 31% to 91% and mortality reduced by 30% to 50% for azaleas planted in natural (nonsterile) PB amended with P. janthinellum compared with the infested control. The population densities of P. janthinellum exceeded 10 5 to 10 6 cfu/g dry PB within 7 days and remained stable over time. Penicillium janthinellum, a natural colonizer of PB container media, shows potential as a biological control of phytophthora root rot of azalea.