A high nitrogen level in the soil stimulated vegetative development of tomato plants and decreased the incidence of infection byB. cinerea. Negative correlations were found between the nitrogen level in the soil on the one hand, and, on the other, the number of stem lesions and the proportion of fruits falling prematurely because of infection byB. cinerea at the stalk. In some experiments, similar negative correlations were found between soil nitrogen and the incidence of infected petioles and trusses. Except for two experiments, no correlation was found between the nitrogen level in the soil and the proportion of infected leaves.
Deleafing by breaking off the petiole close to the stem resulted in the lowest incidence of stem lesions as compared with that resulting when the petiole was cut either about 3 cm or about 5 cm from the stem.