ANNUAL REPORT, 1942 21 



all six selections of Lycopersicon peruvianum (L.) Mill, showed a similar type of 

 immunity. Bulletin 393 embodies the progress and results of several years' work 

 in the development of resistance in tomatoes to Cladosporium. The Bay State 

 variety is showing susceptibility to the new strain of Cladosporium in an increas- 

 ing number of greenhouses. Nevertheless, many growers have accepted the new 

 variety as a choice forcing tomato. Now that resistance to the new or Bay State 

 strain of Cladosporium has been found, it is being utilized in an effort to combine 

 resistance with desirable commercial type. 



Resistance to Tomato Alternaria Early Blight. (E. F. Guba and R. E. Young, 

 Waltham.) Seed of some 37 elementary types of tomatoes offered as possessing 

 significant resistance to Alternaria solani (E. & M.) Jones & Grout were secured 

 for trials at Waltham. These tests were purely exploratory, and if suitable re- 

 sistance appeared, it was the intention to utilize it for breeding purposes in the 

 development of a blight-resistant tomato. Since a large volume of copper fungi- 

 cides is employed in the control of tomato early blight, this stud}- would appear 

 to represent a worthy contribution to the war effort. 



Weather conditions were ideal for the development of early blight, but in spite 

 of repeated artificial inoculations the disease rather consistently became epi- 

 demic only in correlation with a heavy load of fruit and maturity of the fruit. 

 Thus many types remained relatively free of the disease until late m the season 

 and then showed it in severe proportions. The largest and heaviest fruited and 

 earliest maturing types consistently showed a high degree of susceptibility, and 

 only nine types showed resistance. 



Interrelation of Wettable Sulfur, Lead Arsenate, and Lime in Apple Spraying. 



(Departments of Botany, Chemistry, Entomology, and Pomology cooperating.) 

 This project is intended to add to our knowledge of insect and disease control and 

 to assist in making improvements in the apple spraying schedule. On this basis 

 special consideration was given to tenacity of sulfur, scab control, spray injury, 

 and insect control. 



Disease Resistance and Heredity of Carnations. (E. F. Guba cooperating 

 with H. E. White, Waltham.) Eighteen varieties of carnations were scrutinized 

 for their susceptibility to various important fungus diseases. As was to be ex- 

 pected, in view of the wide host range of Rhizoctonia solani, no resistance to this 

 fungus was found. 



Twenty-two varieties were studied for their reaction to Alternaria dianthi 

 (blight). Virginia, New Deal Ward, Minna Brenner, and Hazel Draper 

 showed a moderate to high degree of susceptibility, but not until long after the 

 benching season. The disease has become increasingly insignificant in recent 

 years. 



A high degree of susceptibility to Uromyces rust was shown by Woburn, Oli- 

 vette, New Deal Ward, Hazel Draper, Paragon, Pink Treasure, Johnson's Crim- 

 son, Spectrum Supreme and King Cardinal. 



Tests with the branch rot organism, Fusarium dianthi, and the root rot or- 

 ganisms, F. avenaceum and F. culmoriim, yielded no results. 



Effect of Soil Temperature on Timothy (Phleum pratense L.). (L. H. Jones.) 

 Seedling plants of timothy were transplanted to containers of soil at a high level 

 of fertility. The plants were allowed to establish themselves at a soil temperature 

 of 65° F., after which the apparatus was adjusted to a range of soil temperatures 

 from 50° to 90° at 10-degree intervals. Tiller counts at 50 days showed that soil 

 temperature affected stooling, the number being greater at 70° and tapering off 

 to the extremes of 50° and 90°. At 50° there was a marked tendency for the shoots 

 to be prostrate in habit. This prostrate habit was also noted in a cool greenhouse 



