ANNUAL REPORT, 1943-44 7 



Black Root Rot of Tobacco. (C. V. Kightlinger.) Several strains of Havana 

 Seed have been produced which are capable of producing high yields of tobacco 

 of superior type and quality in soils infested with the organism that causes black 

 root rot as well as in soils free from diseases. Havana Seed 211 is the best of the 

 strains that have been tested thoroughly, but it is not entirely acceptable to all 

 cigar manufacturers. In spite of this fact, this strain is grown in large acreage 

 in the Connecticut Valley and has been an important factor in increasing the 

 average > ield per acre and in improving the qualit}' of Havana Seed tobacco 

 produced in the Valley' during the last several years. 



New strains of Havana Seed are being produced, some of which seem to 

 possess improvements in type, quality, and habits of growth, especially in leaf 

 conformation and in earlier maturity. Two of these strains are being tested in 

 commercial production, and also in the manufacture of cigars by leaders in the 

 business. 



Brown Root Rot of Tobacco. (C. V. Kightlinger.) Since brown root rot often 

 develops on tobacco following other crops, one phase of this study is concerned 

 with the growing of a number of crops deleterious to succeeding crops of tobacco, 

 to see whether unusually large applications of fertilizer will reduce the occurrence 

 and severity of brown root rot on following crops of tobacco. 



The other phase of the work is a study of tobacco grown continuously, to see 

 whether brown root rot can be produced by a low state of fertility and then to 

 study the possible corrective effect of different fertilizing materials. 



It has taken several years to accomplish the preliminary work of getting the 

 soil into the desired condition for a study of the main objective of the project — 

 how low fertility of soil and inadequate fertilization affect the development not 

 only of brown root rot of tobacco, but also of root ailments of several other farm 

 crops. 



Disinfection of Tobacco Seedbeds. (C. V. Kightlinger.) Fall treatments with 

 chloropicrin and calcium cyanamid used singly and in combination, fall and 

 spring steaming, and fall and spring treatments with formaldehyde were used. 

 No noticeable damping-off, bed-rot, or other rcot diseases of tobacco seedlings 

 occurred in the seedbeds during the season; therefore no definite information 

 could be obtained from this year's experiment about the value of any of the soil 

 treatments as disease control measures. 



The spring steamed and the calcium cyanamid treated areas could not be kept 

 moist enough for satisfactory growth of tobacco seedlings because of a temporary 

 change in physical condition of the soil due to the treatments. A further diffi- 

 culty on the calcium cyanamid treated areas was an accumulation of residual 

 substances on and near the surface of the soil, which seemed to be harmful to 

 tobacco seedlings. 



Tobacco seedlings grew much more vigorously in the fall steamed and the 

 chloropicrin treated areas and somewhat more vigorously in the formaldehyde 

 treated areas than they did in the untreated areas. If this was due entirely, or 

 even in large part, to the control of disease, then very slight infections of root 

 diseases retard the growth of tobacco seedlings much more than is generally 

 recognized. It is reasonable to believe, however, that these treatments had other 

 invigorating effects on plant growth besides the control of diseases. 



Fall steaming and chloropicrin treatments were highly effective in the control 

 of weeds in the seedbeds, the fall steaming being somewhat more effective. 

 Formaldehyde gave only slight control of weeds. No weeds grew in the spring 

 steamed and the calcium c\'anamid treated areas at any time during the season. 



