The effect of the two bio-control agents (Trichoderma harzianum and Bacillus subtilis), two agricultural chemicals (sulfur-M and Ca(OH)2) and the fungicide (Topsin-M 70%) as seedling treatments for the control of Sclerotinia sclerotiorum on Centaurea cyanus (blue bottle, “ornamental plant- Compositae Family”) plants during 1999/2000 and 2000/2001 seasons were studied. Results proved that blue bottle plants were susceptible to the Sclerotinia disease. Also, the disease incidence increased more after 3 - 4 months from seedling than 2 months. On the other hand using T. harzianum, sulfur-M and Topsin-M 70% were the most effective against the disease during the first season. Meanwhile, T. harzianum and Topsin-M 70% were effective in the second season. As Topsin and T. harzianum were more effective as it revealed the least length of part disease, number and weight of sclerotia in phloem of diseased plant than other treatments during the two seasons. Concerning the formation of sclerotia (number and weight/plant) which formed on the surface of blue bottle plants, Topsin and Trichoderma significantly reduced the yield of sclerotia. Meanwhile, no significant differences were found between the two agricultural chemicals (sulfur-M and Ca(OH)2) in number of sclerotia/plant and weight of sclerotia/plant.
Regarding the characteristics of vegetative, flowering and root growth, all treatments were effective for improving all these parameters in blue bottle. On the other hand, the bio-control agent T. harzianum and sulfur-M showed to be more effect in controlling S. sclerotiorum than fungicide Topsin during the two seasons.
Also, T. harzianum and sulfur-M increased significantly chlorophyll a and b, as well as total carbohydrates and total phenols (free and conjugated) than Topsin-M 70% in the blue bottle during the two seasons. These study has been important for two reasons: firstly, to control Sclerotinia disease and reducing number of sclerotia which caused the disease on more other crops. The second reason, using some treatments that more safely on the healthy and environments, than fungicides in controlling S. sclerotiorum.
Key Words: Sclerotinia, Centaurea cyanus , bio-control, agricultural chemicals, chemical composition and fungicides
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