26 THE PRODUCTION OF TOBACCO UNDER SHADE. 
Taste IV.—Record of three years’ breeding in Type 13-2-3. 
Total. | 
| ! 
| Year. | Selection. | Wrappers. | Seconds. ‘yield. 
Pounds. | Pounds. Pounds. | 
| -aaO05. ce amet 13-2-3 859 | 304 | 1,163. | 
POG ee 13-2-3 | 970 184} 1,154 | 
1907 Bes eee 13-2-3 1,153 
(S740 340. | 
Table IV shows that for the three years specified the number of 
pounds of wrappers was increased and that the seed plants selected 
in 1906 gave a substantial increase in yield and quality over the 1906 
crop. 
THE STERILIZING OF SEED BEDS. 
The sterilizing of seed beds is a new and very important feature in 
the production of tobacco seedlings. This practice was brought about 
by the general prevalence of a disease known as Thielavia basicola, 
which attacked the roots of the young plants and completely destroyed 
them. This disease made its appearance in 1905 and seemed to spring 
up spontaneously in several sections of the Connecticut Valley. It 
was of so serious a nature that experiments were made at once with a 
view to checking its growth. 
In the spring of 1907 the writer conducted a series of experiments 
on a very badly diseased bed. Sections of the bed were sterilized 
with steam; with formalin, 1 to 200 parts of water, applied at the 
rate of 1 gallon to the square foot of seed bed, and with surface fire. 
The steam sterilization proved to give the best satisfaction, this 
method ¢ not only killing the fungi, but destroying all weed seeds. The 
results were so satisfactory that this practice was recommended to the 
farmers, and a number of them used it in the season of 1908 with 
excellent results. 
The beds are sterilized after they have been prepared for the seed 
and just before the seed is sown. A galvanized pan 10 by 6 feet 
and 6 inches deep (see Pl. IV, fig. 2) is inverted and the edges are 
pushed down into the soil 1 or 2 inches. The pan is connected with 
a steam boiler by means of a steam hose, and live steam is run into 
the pan for about forty minutes under a pressure of from 100 pounds 
up. The higher the pressure the more thoroughly the soil will be 
sterilized. 
To get the results and ascertain the effectiveness of steam sterili- 
zation of seed beds, the following circular was sent out on June 17, 
1908, to all growers who sterilized their beds: 
In order that we may get an idea of the value of steam sterilizing of seed beds for 
the production of tobacco plants, will you kindly answer the following questions and 
return this sheet in the inclosed envelope? 
« Devised by Mr. A. D. Shamel, of the Bureau of Plant Industry. 
138 
