THE MONTHLY BULLETIN. 745 



Control in the Greenhouse and Seedbed. 



Steam.— The best known method of controlling root worms and 

 root diseases in the i2^reenhouse and seedbed is by the use of steam. 

 The establishment of a steam plant in the greenhouse is a rather heavy 

 initial expense, but when once established is permanent and may be 

 operated at a nominal cost. 



Pipes are laid at the bottom of the beds. These may be made of 

 either iron or tiles, perforated at regular intervals of a few inches 

 with holes about one sixteenth of an inch in diameter. The pipes, for 

 good results in sterilization, should not be greater than two feet apart ; 

 a lesser distance would of course reduce the time actually needed to 

 kill all of the worms. Before the steam is turned on the beds should 

 be well covered by sacks, straw, old blankets, or the like, which will 

 hold the heat in the top soil, allowing it to reach a temperature suf- 

 ficient to kill any animal life. 



The best plan in laying the pipes is to arrange them lengthwise in 

 the beds, with the steam inlet located at one end in a cross-piece of 

 pipe running across one end of the bed and into which all of the 

 parallel pipes should open. For successful work it is very essential 

 that no open ends be left in the pipe, as no pressure could be main- 

 tained. 



The greater the steam pressure, the more successful the operation, 

 since the work may be accomplished in muc'h le«s time with the high 

 pressure, which reduces the danger of saturating the soil to such a 

 degree that it may become soggy. The reduction of the soil to this 

 condition should always be avoided. Best results have been obtained 

 with a pressure of 80 to 100 pounds to the square inch, and should 

 never be allowed to fall below 40 pounds. High pressure has many 

 advantages in that it is more efficient in its killing power, destroying 

 all living matter with the possible exception of bacterial spores. _ In 

 the case of soil bacteria, which are very essential to good soils, it is 

 well that they are able to withstand this treatment. A simple and 

 satisfactory method of determining the length of time steaming should 

 be continued is obtained by placing potatoes under the covering on top 

 of the soil in the bed being treated. These, placed in different parts 

 of the bed will, when found to be cooked, indicate that the sterilization 

 has been thoroughly accomplished. 



Formaldehyde. — Of the various chemicals which may be applied 

 in the greenhouse or seedbed, formaldehyde seems to be the most suc- 

 cessful and economical agent. Successful treatment has been obtained 

 in using the following formula: 



Commercial (36 per cent to 40 per cent) formaldehyde 1 part 



Water 100 parts 



Application per square yard 1 to 1^ gallons 



In case of very absorbent soils increase the amount to be used a little. 

 After applying the formaldehyde, efficiency will he increased by 

 thoroughly stiri-ing the soil. Plants vr seeds can not be planted 

 innncdiately after application. The formaldehyde should be allowed to 

 evaporate, this requiring a period of ten days before planting should be 

 attempted. Stirring the soil during this time aids in ridding the soil of 



