الفهرس 
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Abstract
Rhizoctonia solaniis considered as an important soil soilborne fungal pathogen which survive in soil for long time due to formation sclerotia on newly formed potato tuber and causing black scurf symptoms. The fungus infect potato sprouts and stems causing death for sprouts and stem canker. This disease is considered as one of the devastating diseases infecting plants and tubers in field. The disease is distributed in all surveyed governorates, The highest percentage of infection recorded in summer plantation season than nili(Autumn) and winter season mainly in El-Kaloubia and El-Minia governorates. Fifteen isolates of R.solani were isolated from naturally infected stems and tubers. Ten of them were belonged to AG-3 anastomosis group, which severely attack potato plants. These ten isolates grew well on different agar media tested. Potato dextrose and potato agar media were the most favorable for fungus growth. Lady-Roseta, Anova and Herms were the most susceptible cultivars whereas Arezona and Areka were least suscetible. The disease incidence and severity decreased when tuber seeds were kept for sprouting for 21 days than 7 or 10 days, and when tuber were sowed in silty soil than sandy-caly which gave the highest percentage of infection. The percentages of infection decreased when tuber seeds were sown at 4 cm from the soil surface, wherase it was maximum when seeds were planted at 20 cm.Trichoderma harzianum suppreased canker and black scurf disease incidence and gave the best control of the disease, followed by T. viride then B subtilis. Pseudomonas florescence which wee the least affected ones. Eucalyptus leaves extract gave the highest percentages of healthy potato and the lowest both stem canker and black scurf disease severity than worm-wood, white mulberry, Castor oil-plant and spearmint extracts. The fungicide Rizolex gave the highest affectivity in reducing the disease severity followed by Monceren-compy and Copro-Antracol.