ANNUAL REPORT, 1943-44 23 



Control of Greenhouse Vegetable Diseases. (E. F. Guba, Waltham.) With 

 the objective of developing a tomato of desirable commercial type, immune to 

 leaf mold and yielding fruit weighing 3^/^ to 5 ounces each, the Bay State tomato 

 has been hj'bridized with various types which are immune to leaf mold. In the 

 Fa generation, segregations appeared for various degrees of susceptibility and for 

 immunity. The population of totally immune plants varied from 72 to 86 per- 

 cent; and two of the crosses produced tomatoes which averaged 2J^ to 3J^ and 

 2 1/3 to 2 3/4 ounces each, indicating that the objective may soon be realized. 



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

 H. E. White, W^altham.) Project has been suspended for the duration of the 

 war, projects on food production being considered more important. 



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 spray injury. On this basis special consideration was given to tenacity of 

 sulfur, particle size of sulfur, scab and plum curculio control and russet injury. 

 As in the past, detailed reports of the work at Amherst and Waltham are com- 

 piled and submitted to the departments involved. 



Miscellaneous Studies. (E. F. Guba and E. V. Seeler, Jr., Waltham.) 



Control of Cabbage Club Root with Chlor pterin. A plot of ground badly contam- 

 inated with cabbage club root fungus was treated with chlorpicrin, 25 pounds to 

 1000 square feet, two weeks before it was planted to clean cabbage plants from 

 steam-sterilized soil. Growth of the plants was generally poor — in the untreated 

 plot because of club root, and in the treated plot because of club root and chlor- 

 picrin gas persisting in the soil long after application. Although root infection was 

 less in the treated plot, more and better heads developed where the soil had not 

 been treated. This is in line with results of previous tests of various chemicals 

 which have been advocated for controlling club root. Our results over the years 

 show nothing significant In favor of chemicals applied to the field in advance of 

 planting; and we are led to accept the use of new or uncontaminated land 

 as the only practical method of controlling the club root disease under our con- 

 ditions. 



Cooperative Vegetable Seed Treatment Dejuonstration. These demonstrations 

 were sponsored by the American Phytopathological Society in cooperation with 

 the states to study the efificacy of various newer chemical seed treatments, and 

 to standardize the pre-treatment of seeds for the control of seed decay and damp- 

 ing-off. The results of the trials in the different states will be summarized and 

 published in the Plant Disease Reporter ^ U. S. Department of Agriculture. The 

 best chemical treatments for each vegetable type considered at Waltham, rep- 

 resenting the mean of five replicates, are as follows: 



Bean (Lima) Spergon, .20 percent b\- weight 



Bean (Snap) Fermate, .20 percent by weight 



Beet Yellow Cuprous Oxide, 2.0 percent by weight 



Carrot U. S. R. n. 604, 1.5 percent by weight 



Corn (Sweet) Arasan, .18 percent by weight 



Spinach Fermate, .25 percent by weight 



Onion Fermate (excess dosage) 



Pea Spergon, .168 percent; Thiosan, .168 and .335 percent 



