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Poster: Biology & Disease Mgmt: Biological Control


Effect of biopestisides on Phytophthora Root Rot Disease of Oakleaf Hydrangea
M. KABIR (1), P. Liyanapathiranage (1), T. Simmons (1), F. Baysal-Gurel (1) (1) Tennessee State University, U.S.A.

Phytophthora root rot, caused by Phytophthora nicotianae, has been reported to infect almost all hydrangeas especially container-grown oakleaf hydrangea (Hydrangea quercifolia). The pathogen can be introduced into the nursery via Phytophthora-contaminated container stock or cuttings. Experiments were performed in a greenhouse to determine the efficacy of biopesticides and fungicide against Phytophthora root rot in oak leaf hydrangea cvs. Queen of Hearts and Munchkin. Treatments applied were the biopesticides RootShield WP (Trichoderma harzianum Rifai strain KRL-AG2) and RootShield Plus (T. harzianum Rifai strain T-22 and T. virens strain G-41) and fungicide Subdue Maxx (Mefenoxam). All the treatments reduced root rot disease severity compared to the inoculated, non-treated controls in both cultivars. There were no significant differences between the treatments. Root rot disease severity was significantly higher in the cultivar Queen of Hearts than cultivar Munchkin. There was no significant effect of treatment and cultivar on root biomass. This study shows that biopesticides, RootShield WP and RootShield Plus, should be considered to reduce the risk of Phytophthora root rot on container-grown oakleaf hydrangeas in the nursery.