Experiments on the epidemiology and control of Chrysanthemum White Rust, caused by Puccinia Horiana P. Henn

Abstract

The results of experiments on the epidemiology and control of Chrysanthemum white rust caused by Puccinia Horiana P. Henn. are given in this paper.
1. Teleutospores germinate at wide range of temperature from 6°C to 36°C, and optimum lies between 18°C and 28°C. Sporidia are formed at the temperature range between 6°C and 24°C, and optimum lies between 13°C and 22°C. On the affected leaves, sporidial formation is observed 6 hours after incubation at 24°C in the dark, but is inhibited by the light.
2. Sporidia germinate at wide range of temperature from 6°C to 36°C and optimum lies between some 13°C and 18°C. The light showed no effect on the germination of sporidia.
3. According to the results of the inoculation experiments, incubation period of the disease is about ten days long.
4. Teleutospores on sorus lost their vitality after 20 days in the laboratory condition in May, but at 32% of relative humidity they survive for 30 days long.
5. Sodium pentachlorophenate (PCP-Na), wettable sulfur (Soid) and flower of sulfur showed remarkable effect in retarding the germination of teleutospores on the leaves, but ammonia bordeaux, copper-mercury fungicide, mercury fungicide and lime sulfur showed little effect in retarding the germination of spores.
6. Wettable sulfur (Soid) showed the most remarkable effect in retarding germination of sporidia, and flower of sulfur and Ceresan-lime dust were the next. And yet Phygon, SR-406 and lime sulfur showed also considerable fungitoxicity.
7. Dusting of wettable sulfur seems to be effective in controlling the present disease.