58 



SCIENTIFIC AGRICULTURE 



October 



Stem-Rot of Sunflowers in Manitoba 



By U. R. BIJSBY, 



Professor of Botany, Manitoba Agri- 

 cultural College. 



The cultivated sunflower (Jleliuitlhus 

 a nil Hits) is coming to hold a very impor- 

 tant place as a silage crop in Western 

 Canada and in ether regions where corn 

 does not thrive. Rust sometimes defoliates 

 sunflowers to some extent, and other leaf 

 diseases may cau.se .slight reduction in the 

 forage value of tiie crop ; but in general, 

 tlie plant is considered fairly free from 

 disease. During 1920 and 1921, however, 

 the disea.se mentioned below assumed con- 

 siderable importance in Manitoba. 



This disease may be called "stem-rot"' 

 or "wilt'", as eitlier name expresses a 

 conspicuous symptom. "Crown-rot" would 

 be very appropriate for the most common 



Figure 1. — Shows willing of the plants in the 

 field, August 10th. 1921. 



early appearance of the disea.se ; but often, 

 much more than the crown is affected and 

 sometimes the crown itself may be normal 

 while some upper portion of the plant is 

 attacked. Since the name "wilt" as ap- 

 plied to plant diseases so commonly im- 

 plies a clogging of the vascular tissue with- 

 out external rot, it would seem that "stem- 

 rot" is as applicable as any common name 

 for this disease. 



The same or a similar disease of cul- 

 tivated sunflowers was reported in 1912 

 by Lawrence (6) from the state of Wash- 

 ington, and attributed by him to a new 

 species of Sclerotinia, S. perplexa. The 

 disease apparently received little atten- 

 tion subsequently until 1920, when it was 

 reported as common in Montana (7). 

 Manitoba (1), Ontario (4), Oregon and 

 Washington (8). It was also found in 

 Minnesota for the first time (8). Mpi'ris 

 and Swingle (7) consider the fungus to 

 correspond closely to Sclerotinia lihertiavn 

 Fcl., which is known to attack a large num- 

 ber of hosts, particularly vegetables. Bro- 

 drick found 8. Ubertiana in 1919 on pars- 

 nips in Manitoba (2), specimens being sent 

 to Dr. G. H. Coons who made the deter- 

 mination. It has also been reported on 

 carrots (3, 9). The writer found Sclero- 

 tinia on both parsnips (see fig. 2) and 

 carrots at Winnipeg in the fall of 1920, re- 

 sembling the fimgus found on sunflower, 

 and inocidations showed that the fungus 

 isolated from sunflower would attack car- 

 rots and parsnips. Jagger (5) has i-c- 

 cently described a new species of Sclero- 

 tinia which is characterized by smaller 

 sclerotia than are produced by 8. librrfin- 

 va. The writer has not definitely detei- 

 mined the species of Sclerotinia causing the 

 sunflower disease in Manitoba, but caji at 

 least agree with Morris and Swingle as to 

 its resemblance to -S^. iihertiava. Conidia 

 such as Lawrence described were not found 

 in cultures of the fungus, although mi- 

 croconidia are to be found. 



The disease has been found in Manitol>« 



