ANNUAL REPORT, 1940 19 



COOPERATIVE TOBACCO INVESTIGATIONS 



Conducted by the Bureau of Plant Industry, United States Department of 

 Agriculture in Cooperation with the Massachusetts Agricultural Experi- 

 ment Station. 



C. V. Kightiinger, U. S. D. A., in Charge 



Black Root-Rot. (C. V. Kightiinger.) Black root-rot is one of the 

 most important diseases of tobacco in the Connecticut Valley. The project 

 to develop new strains of Havana Seed which are more resistant to black 

 root-rot and acceptable in type, yield and quality in the Connecticut Valley, 

 is consequently being continued. 



Selections from Havana No. 211 have been made to improve the strain. 

 New strains have been produced by crossing strains of Havana Seed that 

 are resistant to black root-rot with strains of common Havana Seed that 

 are highly approved for type and quality. Selections from the progeny of 

 these new strains and tlier back-crosses are being tested. 



Soil Treatments for Tobacco Seedbeds. (C. V. Kightiinger.) Damping- 

 off diseases and weeds in tobacco seedbeds are important in tobacco 

 growing in the Connecticut \'alley. Treatments to control tliese troubles 

 are consequently important. 



Most of the large tobacco growers in the Connecticut Valley steam 

 sterilize their seedbeds in the fall; a few steam treat their seedbeds in 

 the spring. The practice of sterilizing tobacco seedbeds, however, is not 

 so general in the Connecticut Valley as it should be. It is probable that 

 more growers would sterilize their seedbeds if steaming equipment were 

 not so expensive, or if other recommended methods did not cause incon- 

 venience in application and delay in seeding. A method other than steam 

 sterilization which would be effective, cheap, and convenient to use in 

 controlling damping-off diseases and weeds in seedbeds, would mean much 

 to the tobacco growing business in the Connecticut Valley. 



Seedbeds which have been steam sterilized in the fall sometimes develop 

 damping-off troubles because of subsequent contamination. Carelessness 

 on the part of men working around the seedbeds may cause a large part 

 of the contamination; but wind-blown earth, which is fairly common in 

 the Connecticut Valley during the winter and spring of most years, is 

 responsible for a considerable part of the contamination. Supplementary 

 spring treatments for seedbeds steam sterilized in the fall, which would 

 be effective against damping oft', cheap, and convenient, \\'ould be a val- 

 uable aid. 



Experiments were begun in tlie fall of 1940 to test tlie effectiveness of 

 certain other treatments in comparison with steam sterilization, to control 

 damping-off diseases and to kill weeds in tobacco seedbeds. The experi- 

 ments include both fall and spring treatments. Preparation for the test 

 was begun a year earlier by maintaining a seedbed to which earth infested 

 with damping-off organisms obtained from seedbeds in various places in 

 the Connecticut Valley, was applied during the spring and sunmier, to 

 assure the presence of various types of damping-off organisms. Tobacco 

 seedlings were grown from time to time in the seedbed throughout the 

 spring and summer to increase the supply of damping-off organisms. 

 Damping-off of tobacco seedlings was occurring in this seedbed when the 

 soil was worked to prepare it for fall treatments of the experiment. 



