|Authors: ||H. Suheri, T.V. Price|
|Keywords: ||Alternaria porri, Stemphylium vesicarium, purple leaf blotch, epidemiology, leaf wetness, temperature|
Infection of onion leaves by Alternaria porri at 5°C, required 16 h or more of leaf wetness duration but only 8 h at 10-25°C. The number of lesions increased with increase of temperature and leaf wetness duration.
Under field conditions, disease incidence was higher during spring and autumn than during summer.
Longer leaf wetness periods occurred during autumn than during summer.
Spore trapping revealed that both A. porri and S. vesicarium spores were present in the air, indicating that both were responsible for increased disease incidence during the growing seasons.
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