ANNUAL REPORT, 1945-46 11 



Meanwhile, work is being done to effect further improvements: first, by select- 

 ing the most desirable plants within the strains already produced to improve 

 habits of growth as well as type and quality; and second, by breeding entirely 

 new strains. 



Brown Root Rot of Tobacco. (C. V. Kightlinger.) Ordinarily, but not always, 

 tobacco grown immediately following corn, grasses, and a few other crops de- 

 velops brown root rot in some degree, in the Connecticut Valley. It is probable 

 that more than one factor may be responsible for this irregular occurrence of the 

 disease; but it is natural to suppose that soil fertility may be one of the most 

 important. With this in mind, experimental work is now in progress, as follows: 



1. Crops know-n to produce brown root rot promoting soil conditions under 

 usual fertilizing practices are being grown with more than the usual amounts of 

 fertilizer, to determine what effect this will have on the following crop of tobacco. 

 Results are not yet available. 



2. Different amounts of fertilizer are being used on tobacco following crops 

 known to produce brown root rot promoting soil conditions, to determine whether 

 fertilizer can be so used as to prevent the development of the disease following 

 these crops. Results are not yet available. 



3. Tobacco is being grown continuously on the same land, with inadequate 

 fertilization, to ascertain whether the disease will develop under these condi- 

 tions. It has been definitely determined experimentally that brown root rot will 

 develop, in moderate degree at least, on tobacco that is grown continuously on 

 the same land under certain inadequate fertility conditions. This result, in 

 connection with the well-known fact that brown root rot may be overcome, in 

 the Connecticut Valley at least, by growing tobacco continuously on brown root 

 rot promoting land for three or four years under usual tobacco fertilizing practices, 

 suggests that malnutrition may be important in the development of the disease. 

 Further tests are necessary. 



Control Measures for Mildew of Tobacco. (C. V. Kightlinger.) In experi- 

 mental work to test the comparative effectiveness of different materials in the 

 control of mildew of tobacco in seedbeds, Fermate and bismuth subsalicylate used 

 in recommended concentrations gave complete control of the disease in 1946. 

 Mildew developed in moderate severity in the untreated check. The materials 

 were applied at weekly intervals with sprayer at 150 pounds pressure. Eight 

 applications were made throughout the season, beginning May 3, before any 

 cases of mildew in tobacco seedbeds had been reported. 



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

 tatoes of seven varieties grown regularly in the State (Chippewa, Katahdin, 

 Earlaine, Sebago, Irish Cobbler, Green Mountain, and Russet Rural) were treated 

 with cold mercuric chloride plus acid, cold formaldehyde plus acid, Semesan Bel, 

 Sanoseed, Fermate, andSpergon, to ascertain the relative tolerance of the vari- 

 eties to disinfecting treatments and the comparative effectiveness of the treat- 

 ments in the control of scab and rhizoctoniose. 



Mercuric chloride and formaldehyde caused little injury to tubers of the Irish 

 Cobbler, Green Mountain, and Russet Rural varieties; moderate injury to tubers 

 of the Katahdin, Earlaine, and Sebago varieties; and more severe injury to tubers 

 of the Chippewa variety. These treatments caused reductions in stands of po- 

 tatoes in the field ranging from slight, in the case of Irish Cobbler, Green Moun- 

 tain, and Russet Rural; moderate to heavy in case of Katahdin, Earlaine, and 

 Sebago; and severe in the case of Chippewa. Semesan Bel, Sanoseed, Fermate, 

 and Spergon caused no noticeable injury to the tubers of any of the varieties 

 before planting; but Semesan Bel and Sanoseed had some detrimental effects on 



