Some Aspects of the Effect of Relative Humidity on Growth of Celery Leaf Spot

Abstract

The effects of relative humidity on the germination of spores of Septoria apiicola Speg. and on the infection of Celery plants variety Utah 52-70 by this fungus were studied. Germination occurred at humidities between 100% and 92% R.H. and infection between 100% and 95% R.H. The minimum period of high humidity needed for infection to occur was 24 hours for both young and old plants. This 24 hour period could be broken into 2 or 3 shorter periods separated by up to 8 hours of 80% R.H. Storage affects viability of spores and also infection of Celery plants by this fungus.