Study On Disease Development And Chemical Control Of Rhubarb Ring Spot In Qinghai

disease is serious and destructive. In this paper, the development of rhubarb ring rot disease was investigated. Also, the chemical control of disease was carried out. It was preliminary to know the occurrence of rhubarb ring rot disease and control rhubarb ring rot disease with chemicals in Qinghai. Major results were as follows:1. Disease leaf of rhubarb ring rot in field appeared in early June. The disease incidence showed an increasing trend. In the ten days of June rhubarb ring rot was a stage of beginning, and reached a peak form the twenty days of June to the twenty days of July. Then rhubarb ring rot showed very serious in the twenty days of August, dead plants happened in the ten days of September. It was key stage to control Ring rot disease in the ten days of June, and disease condition developed quickly in the twenty days of June. Factor of disease condition was related to rain in June and July.During the August 4 to September 5, the disease condition did not rise any more. 2. Inhibition of mycelium growth with different chemicals in indoor was tested and results indicated that four chemicals, including 50% NA WP, 50% Pyrimethanil WP, 10% ShuangXiaoLing WP and 50% Carbendazim WP, showed significant restraining rate with 90% or so. Other chemicals showed worse restraining rate.3. By controlling effect on rhubarb ring rot disease in field with chemicals, results showed that the controlling effect of 50% NA WP, 50% Pyrimethanil WP, 50% Carbendazim WP were above 80%. The controlling effect of 69% Dimethomorph plus mancozeb WP and 75% Chlorothalonil WP were 66.38% and 50.81% respectively.