SCLEROTINIA MINOR, N. SP., THE CAUSE OF A DECAY 

 OF LETTUCE. CELERY, AND OTHER CROPS 



By Ivan C. Jagger 



Pathologist, Office of Cotton, Truck, and Forage Crop Disease Investigations, Bureau of 

 Plant Industry, United States Department of Agriculture 



Smith 1 (1900) recorded the occurrence of a fungus similar to Sclerotinia 

 libertiana Fuckel, which, however, produced much smaller sclerotia 

 (PI. 59, A) in greenhouses of Massachusetts, where it was causing a 

 destructive rot of lettuce. Duggar 2 (1909) states that a similar fungus 

 occurs on lettuce in the vicinity of both Boston and New York City. 

 In 191 1 the writer 3 obtained what appeared to be the same fungus from 

 decayed lettuce grown in the vicinity of New York. It was collected 

 in 1 91 2 and again in 191 4 at South Lima in western New York, where it 

 seemed to be well established and was causing considerable injury to 

 lettuce grown on muck soil. In 1 914 it was also collected on lettuce in a 

 greenhouse at Rochester, N. Y., but the fungus was not again found in 

 that vicinity, although numerous collections of diseased lettuce were 

 made during the next three years. In the fall of 191 9 Dr. W. S. Beach 

 of the Pennsylvania Agricultural Experiment Station advised that the 

 fungus is frequently found on celery and lettuce in the vicinity of Phila- 

 delphia. During the winter season of 1919-20 the writer observed the 

 fungus in destructive amounts in a single field of lettuce at Sanford, Fla. 

 In numerous inspections of lettuce in that vicinity throughout the 

 season the fungus was observed in no other fields, although 5. libertiana 

 was more or less abundant in all fields. This suggests that the fungus 

 forming small sclerotia may have been recently introduced into that 

 section. 



The fungus causes a very rapid decay and collapse of growing lettuce 

 plants. The disease produced is almost identical with that caused by 

 S. libertiana. A soft, watery decay may begin at any point on the plant 

 but usually on the lower leaves, which rest on the ground, or on the 

 stem near the ground. The rot spreads very rapidly, and usually the 

 main stem and bases of the leaves are soon involved. The result is a 

 rather sudden collapse of the whole plant. The plant is rapidly con- 

 verted to a soft, watery mass. When the decayed mass is pulled apart 

 the spaces between and around the decayed leaves and stem are found to 



1 Smith, Ralph E. botrytis and sclerotinia: their relation to certain plant diseases and to 

 Each other. In Bot. Gaz., v. 29, no. 6, p. 369-407, pi. 25-27. 1900. 



2 Duggar, Benjamin Minge. fungous diseases of plants ... p. 198. Boston, [1909]. 



3 Jagger, Ivan C the small LETTUCE sclerotinia, an undescribed species. (Abstract.) In Phyto- 

 pathology, v. 3, no. 1, p. 74. 1913. 



Journal of Agricultural Research, Vol. XX, No. 4 



Washington, D. C Nov. 15, 1920 



vt Key No. G-211 



(33 1 ) 



