CONTROL OF BACTERIAL WILT 1d 
TaBLeE 7.—Control of wilt by chloropicrin treatment of the soil 
Tobacco plants wilted on— 
Rate per square foot (cubic centimeters) | Plot = |——— 
July 1 July 15 | Aug.1 | Aug.15 | Sept. 1 
Percent | Percent | Percent | Percent | Percent 
fi 1 58 | 98 100 100 | 100 
ee 2 73 | 92 94 100 100 
fl 07 2 10 21 | 77 
Teenie ete \2 0 | 0 10 10 75 
3 Bl 0 0 0 4 | 46 
mea ig eT ee TS \2 0 0 0 4 30 
{i 0 0 0 2 | 31 
er ee 2 0 0 4 7 | 22 
SA SL ee ee ne 1 0 0 4 4 | 19 
| | 
1 Approximately 48 plants per plot. 
Tests With ComMPLEX ORGANIC COMPOUNDS 
The results obtained on several plant and animal pathogens with biologically 
synthesized materials (8) suggested that some of the more complex organic 
compounds might be of value as soil treatments. Fifty-three compounds, some 
of which are synthesized by micro-organisms in culture, were tested in the green- 
house or in the field as soil treatments at rates of 12.5, 25, or 50 pounds an acre. 
Some of the compounds were highly toxic for tobacco at the lower rate, but none 
of them reduced wilt severity. 
MODIFICATIONS OF CULTURAL PRACTICES 
Several modifications of the usual cultural practices were made, to observe 
their effect on wilt development. Tobacco was transplanted through mulch 
paper and grown without further root injury from cultivation. Many plants 
remained apparently healthy until midsummer, but all were finally killed by the 
wilt disease. In a date-of-planting experiment, tobacco was set April 26 and 
May 25, 1939. The disease developed first on the early planting, but both plant- 
ings were uniformly and badly diseased on July 1. Tobacco and corn were 
grown in alternate hills, spaced 12 and 30 inches apart in the same row, but all 
tobacco was killed by the disease. Many farmers believe that opening the 
tobacco rows with two furrows of a large moldboard plow after harvesting is com- 
pleted helps control wilt. ‘This is a good practice for several reasons, but it did 
not modify wilt severity. In another test the soil was turned with spades to 
depths of 5, 7, 9, and 13 inches. The tobacco plants on all plots were killed by 
the disease, which developed most rapidly on the plot spaded 13 inches deep. It 
was concluded that such variations in cultural methods do not lessen the severity 
of the disease. 
ERERATURE CIIED 
(1) Crayton, E. E., and Smiru, T. E. 
1942. RESISTANCE OF TOBACCO TO BACTERIAL WILT (BACTERIUM SOLANA- 
CEARUM). Jour. Agr. Res. 65: 547-554, illus. 
(2) Crarton, W. W., and WELLs, B. W. 
1934. THE OLD FIELD PRISERE: AN ECOLOGICAL sTuDY. Elisha Mitchell 
Sci. Soc. Jour. 49: 225-246, illus. 
(3) GarRNneER, W. W., Wo tr, F. A., and Moss, E. G. 
1917. THE CONTROL OF TOBACCO WILT IN THE FLUE-CURED DISTRICT. 
U.S. Dept. Agr. Bul. 562, 20 pp., illus. 
(4) NortH CaroLiIna AGRICULTURAL EXPERIMENT STATION. 
1930-88. [SoIL TREATMENTS FOR GRANVILLE OR BACTERIAL WILT CONTROL| 
N: C. Agr. Expt. Sta. Ann. Rpt. (1930) 53: 104; (1931) 54:-80; 
(1932) 55: 36; (1933) 56: 24; (1934) 57: 35; (1935) 58: 29; (1936) 
59: 34; (1987) 60: 35; (1938) 61: 24. 
