A simple and reliable method for evaluating the effectiveness of fungicides for control of powdery mildew (Sphaerotheca macularis) on strawberry [Fragaria ananassa]
1995
Okayama, K. (Nara-ken. Agricultural Experiment Station, Kashihara (Japan)) | Nakano, T. | Matsutani, S. | Sugimura, T.
A simple and reliable method was established for evaluating fungicide efficacy in the control of strawberry powdery mildew. The lower surface of newly developed leaflets of strawberry runner-tip plantlets was the best for assay inoculation, and disease severity could be visually evaluated with ease 7 days after inoculation. The youngest leaflets were more susceptible than the intermediate leaflets, and the oldest leaflets were hardly infected by the fungus. The colonies on the inoculated lower surface of runner-tip plantlets were observed clearly 7 days inoculation and remained alive for 28 days. Disease severity was consistently high when sprayed with conidial suspension containing more than 5.0 x 10(4) conidia/ml. Maximum infection of inoculated leaflets was observed when incubated at near 20 degrees C. Infection frequency at 15 degrees C was greater than at 25 degrees C. No disease development was observed at or above 30 degrees C. When leaflets were sprayed with effective fungicides before inoculation, disease development was remarkably suppressed. The effects of fungicide were more clearly evaluated with leaflets in test tubes than those on whole plant sin the vinyl-covered house. These results indicate the validity of this method for the accurate evaluating of fungicide effectiveness. This method will be adapted to the screening of fungicides for powdery mildew control
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