MANAGEMENT OF ROOT ROT DISEASE IN ORNAMENTAL NURSERIES

Abstract

Kirolos Magdy Adolf Saied: Management of Root Rot Disease in Ornamental Nurseries. Unpublished M.Sc. Thesis, Department of Plant Pathology, Faculty of Agriculture, Ain Shams University, 2016. Root rot disease affects a wide range of ornamentals in home and commercial landscapes, nurseries, and greenhouses. The present study identified major fungal pathogens causing root rot disease in six ornamental plants, i.e. Carnation, Geranium, Hollyhock, Hopbush, Orange Jessamine, and Pothos, collected from nurseries in five different locations in Egypt during 2012-2013. The most frequently isolated fungi were identified as Fusarium spp. (94%). These include: F. semitectum, F. solani, F. equiseti, F. chlamydosporum, F. subglutinans, F. scirpi, F. oxysporum, F. anthophilum, F. verticiloides and F. proliferatum. In addition, three isolates of Phytophthora spp. and an isolate of Pythium ultiumum were also isolated. Variation in pathogenicity of these isolates on Geranium and African marigold plants were established. In vitro assays, 16 bacterial and fungal isolates, have shown antagonistic activity against five tested fungal pathogens isolates. The most antagonistic were Pseudomonas fluorescens (strain3339) and Trichoderma harzianum (TCNu 1) which greatly reduced pathogens mycelial growth. In greenhouse experiments with Geranium and marigold, P. fluorescens (strain3339) was superior to T. harzianum (TCNu 1) in reducing root rot severity and improving plant growth characters. Solarization of pathogen-infested potting soil and the addition of bio-agent or organic amendments had positive effects on plant growth of marigold plants and significantly suppressed root rot severity. Growth and infection of marigold plants by root rot disease. No significant effect of soil solarization on total chlorophyll content of marigold plants. However, plants grown in soil amended with garlic powder or compost showed high chlorophyll content. Activity of polyphenol oxidase enzyme of marigold plants were high in plants grown in un-solarized soil, while there was no significant effect between treatments or solarization on activity of peroxidase enzyme. In conclusion, solarization of potting soil for 8-10 weeks, during summer in Egypt, in plastic bag, has prove high potential to be considered as a useful soil disinfectant, and is an inexpensive, fast, and effective technique for recycling pathogen infested soil. Combining solarization with either bio-agents or compost or vermicompost for ornamental nurseries and greenhouses production will have higher horticultural value besides being an environmentally safe and an inexpensive alternative for soil disinfestations.