CONTROL OF TOBACCO WILT IN THE FLUE-CURED DISTRICT. 5 



the spread of the disease has been rather rapid, so that now but few 

 farms are free from it. The disease has not spread so rapidly out- 

 side of this section, although it has long since crossed the above- 

 mentioned rivers. It has reached the adjoining counties of Vance, 

 Durham, Wake, and Franklin and also has been found in Ashe, 

 Guilford, Greene, Chatham, Davidson, and Yadkin Counties. It is 

 quite possible that tobacco wilt also exists in other sections of the 

 flue-cured district. Although the outward spread of this wilt is not 

 particularly rapid, its progress is none the less certain, and ome 

 established it is exceedingly persistent and exceptionally destructive. 



SUSCEPTIBILITY OF SPECIES AND VARIETIES OF TOBACCO 



TO THE WILT. 



In dealing with the problem of control the first line of attack was 

 the search for resistant varieties of tobacco. The simplest solution, 

 of course, would be the discovery of a resistant type in the standard 

 native varieties used in growing flue-cured tobacco. Failing in this, 

 the next step would be to find a resistant type among the numerous 

 varieties used in growing other classes or kinds of tobacco which are 

 produced in this and foreign countries. If such a resistant type 

 could be found, it could be crossed with the native flue-cured varieties 

 with a fair prospect of obtaining a new variety combining the re- 

 sistant properties of the foreign with the commercial qualities of the 

 native varieties. For several years past extensive tests have been 

 made with nearly all available varieties, including many from foreign 

 countries, but while some varieties have been found to be less sus- 

 ceptible than others the resistance was not sufficient to meet practical 

 requirements. Although the final results were negative, it seems 

 desirable to summarize briefly the work along these lines. In making 

 the tests the general plan has been to grow the different varieties in 

 rows side by side on soil known to be badly diseased, including occa- 

 sional rows of a standard native variety, so as to measure the rela- 

 tive degree to which the different parts of the field were diseased. 

 Records of the number of healthy plants and the number dead or 

 wilted were made at intervals during the growing period, the last 

 records being taken when the plants had reached maturity. 



In the first tests, made in 1904, 62 varieties or types known by 

 distinctive varietal names were used. 1 These included some 25 

 subvarieties or strains of Oronoco, several of the Pryors, White 

 Burley, Maryland, the Broadleaf, or Seedleaf, and Havana Seed 

 types of the northern cigar-leaf districts and domestic and imported 



1 For further details of the tests, see Stevens, F L. (9). 



