30 



BULLETIN 1045, TJ, S. DEPAETMENT OF AGRICULTURE. 



DISEASES OF SUNFLOWERS. 



Rust*' is the most destructive disease of sunflowers. (Fig. 8.) 

 It is common in southern Eussia and has been reported at several 

 points in the United States. Rust was prevalent on these plants 

 at Hays, Kans., in 1920, and has done considerable injury to sun- 

 flowers in experiments at both the Michigan and Wisconsin stations. 

 It decreases very decidedly the yield and also results in a poor 

 quality of silage. 



The best method of preventing rust injury appears to lie in the 

 development of a rust-resistant variety. Frank Spragg and E. E. 

 Down, in reporting on a variety test of sunflowers at the Michigan 



Fig. 8. — Mammoth Iwu.ssiu.ii yunllowcra wilU the lo\;er Icavx's killrd ljy iiisi ai the Hays 

 Branch Station, Hays, Kans., 1920. 



station in 1918 (see Mich. Agr. Quar. BuL, v. 2, no. 3, p. 128-129, 

 1920), claim for the South American variety Kaeurpher a certain 

 measure of rust resistance. It may be, therefore, that a resistant 

 variety will soon be found. 



Some work in breeding a rust-resistant sunflower has been done in 

 Russia. It was found by the investigator, F. A. Sazyperov, that 

 the ornamental sunflower {Tlelianthus agyrophyUus) is resistant 

 to the rust. None of the ordinary commercial varieties are known 

 to be rust resistant. Hybrids w^ere therefore made between one of 

 the commercial varieties and the ornamental sunflower. In the 

 second generation one-fourth of the hybrid plants were found re- 

 sistant to the rust, although the season was exceptionally favorable 

 to the spread of the disease. Among these resistant plants were 



"Rust (Puccinia helianthi Schw.), the damping-off fungus (Ptjthhim dehari/aniim 

 Hesse), downy mildew {Plasmopara luilstedii Far!),, powdery mildew {Eri/fflphe ei- 

 choraeearum) , and wilt (ffclcrothii-a sp.), in addition to the parasitic plants Orobanche 

 cumana Wall, and Homeosonia nehulella Hb. are all said to attack sunflower plants. 



