10 MASS. EXPERIMENT STATION BULLETIN 441 



The most desirable plants within the existing strains are being selected and 

 propagated to improve habits of growth in general and type and quality in par- 

 ticular. Still other strains are being produced by crossing plants that embody 

 the desirable properties of the different strains in highest degree. 



Potato Seed Treatments. (C. V. Kightlinger and H. M. Yegian.) Seven vari- 

 eties of potatoes (Green Mountain, Irish Cobbler, Russet Rural, Katahdin, 

 Chippewa, Sebago, and Earlaine) and eight seed treatments were used to ascer- 

 tain the comparative tolerance of common varieties of potatoes to the treatments 

 and also their effectiveness in controlling rhizoctoniose and scab. The materials 

 used were corrosive sublimate, corrosive sublimate plus acid, cold formaldehyde 

 plus acid, Semesan Bel, Sanoseed, Spergon, Fermate, and Thiosan, all prepared 

 and used according to recommendations. The potatoes were dormant or only 

 slightly sprouted at the time of treatment. 



The inorganic materials caused little if any noticeable injury to tubers or re- 

 duction in stands of Green Mountain, Irish Cobbler, and Russet Rural; slight 

 injury to tubers and moderate reduction in stands of Katahdin, Sebago, and 

 Earlaine; moderate injury to tubers and heavy reduction in stand of Chippewa. 

 The organic materials caused no noticeable injury to tubers of any variety and 

 no reduction in stands of Green Mountain, Irish Cobbler, and Russet Rural; 

 little reduction in stands of Katahdin, Sebago, t nd Earlaine; and moderate re- 

 duction in stand of Chippewa. Injury to tubers consisted not only of injury to 

 eyes and sprouts but also of pitting of the tubers. The treated and untreated 

 potatoes of each variety were taken from the same lot; therefore, it seems rea- 

 sonable to conclude that the reductions in stand were caused by the treatments 

 and not by rhizoctoniose on the sprouts before they emerged from the ground. 



None of the seed treatments seemed to increase the vigor of the plants. On 

 the contrary, there seemed to be some retardation in the emergence of plants 

 from the treated seed of some of the varieties. There were no consistent differ- 

 ences in the amounts of infection of rhizoctoniose, either on the growing plants 

 when about a foot tall or on the tubers grown from treated and untreated seed. 

 Although these experiments yielded no specific information on the effectiveness 

 of disinfecting treatments to prevent injury by Rhizoctonia to the 3'oung sprouts 

 before they emerge from the ground; nevertheless, on the basis of the results 

 obtained, it seems reasonable to conclude that the use of disinfecting seed treat- 

 ments is of doubtful value in preventing the development of rhizoctoniose on 

 the stems and tubers of potatoes. 



Little or no scab developed on any of the potatoes at any time in these ex- 

 periments, so they yielded no information regarding the effectiveness of these 

 disinfecting seed treatments for controlling scab. However, owing to the wide- 

 spread occurrence of the scab-causing organism (like the rhizoctoniose-causing 

 organism) in most cultivated land, and the fact that the scab disease develops 

 late in the growth of potatoes, the use of disinfecting seed treatments would seem 

 to be of doubtful value for controlling scab. Satisfactory control of both rhi- 

 zoctoniose and scab of potatoes must be sought by other means than the use of 

 disinfecting seed treatments. 



Fertilizer Placement for Potatoes. (C. V. Kightlinger and H. M. Yegian.) 

 Green Mountain potatoes were grown on one-twentieth acre plots, replicated 

 four times. Approximately one ton per acre of 5-8-7 fertilizer was applied in 

 four different ways: all banded, two-thirds banded and one-third broadcast, 

 one-third banded and two-thirds broadcast, and all broadcast. The bro£.dcast 

 fertilizer was applied and harrowed into the soil before the potatoes were planted. 

 The potatoes were planted on May 20; sprayed with Bordeaux mixture at weekly 



