RELATION OF WEATHER CONDITIONS TO ONION BLAST

During the recenit period ineluding the years of 1925 to 1940 there have been seven years in which the crops from onion seed suffered a serious leaf injury resulting in low yields. The disease is apparently physiological, for there has not been a single instance in either past or recent investigations that showed the presence of a pathogen when the plants exhibited the first signs of injury. The hypothesis that the causal agent is a certain combination of weather conditions has been substantiated by observation and also by laboratory experiments simulating the environmental factors that approximate the weather conditions prevalent preceding and during the appearance of the injury. Onion blast symptoms