Damping-off and root rot are the most troublesome and common fungi diseases attack avocado (Persea americana Miller) which affecting seedling production and causing serious losses in the number of seedlings in nurseries and transplants in new orchards. Nursery and greenhouse experiments on pre- and post-emergence damping-off of avocado were conducted at El-Qanater El-Khairia Horticulture Research Station, Agricultural Research Center throughout 2016 and 2017 growing seasons. Hass, Eitinger and Fuerte were the most susceptible cultivars to damping-off and root rot diseases, followed by Duke. Whereas, the lowest percentage of pre- and post-emergence damping-off and the highest percentage of survival plants were recorded on Reed, Benkerton and Bekon. Pathogenicity tests on avocado seeds and seedlings under greenhouse conditions showed that F. solani, F. moniliforme, F. semitectum and L. theobromae which isolated from roots of either seedlings in nursery or transplants in new orchards were pathogenic but varied at different degrees in their pathogenicity. Fusarium solani was the most pathogenic fungi causing the highest percentage of pre- and post-emergence root-rot followed by F. moniliforme. On the other hand, the least pathogenic ones were F. semitectum and L. theobromae. To overcome this problem, single treatment of nine compounds i.e. Topsin M70WP, DithaneM-45 80%WP, Kema-Z 50% WP, Rizolex–T 50% WP, Salicylic acid, Bio Zeid 2.5%, Bio Arc 6.0 %, Lemongrass and Thyme oil were used as seed dressing and soil drenching to investigate their effect in reducing damping-off and root rot disease incidence under greenhouse conditions. All compounds reduced the avocado damping-off and root rot disease incidence and increased the percentage of survival plants comparing with untreated seeds or untreated soil. Seed dressing and soil drenching with fungicides (Topsin M70, Kema-Z, Rizolex–T and Dithane M-45) showed a superior effect which produced the highest level of the disease control with the highest number of survived plants. Treatments with biofungicides (Bio Zied and Bio Arc) gave moderate effect. Essential oils (Thyme and Lemongrass) and Salicylic acid reduced the disease and increased mean survival plants of avocado transplants. Best results were obtained when the compounds were applied as seed dressing