INSECT CONTROL IN" FLOUR MILLS. 29 



Kansas, Ohio, Nebraska, Illinois, Indiana, Iowa, southern Canada, 

 Virginia, and elsewhere are equipped for and are using the heat 

 method. The result of all this work is that to-day the heat method is 

 recognized as the most effective, practical, and inexpensive of all 

 treatments, and has the added advantage of being absolutely safe. 

 The greatest expense is the original installation of radiating surface. 

 Yet this expense is offset by the greater cheapness of the heat method 

 as compared with any other effective control measure. Goodwin, 4 an 

 experimenter in Ohio, claimed in 1912 that for a mill of average size, 

 forced to apply remedial measures, the cost of steam piping necessary 

 to obtain killing temperatures was offset within five years by the 

 saving due to the cheapness of the heat method. 



Heat Applied Most Effectively in Summer. 



It is advised that heat be applied during the summer months in 

 order that the normally high temperatures then obtaining may be 

 turned to the advantage of the miller. It is much easier to raise the 

 temperature of a mill to the killing point when the outdoor tem- 

 perature is 85° F. or above. It takes less fuel and less radiation sur- 

 face and saves time. Take advantage of summer heat. Heat only 

 in quiet weather ; it is impossible to get uniformly good results dur- 

 ing windy weather. 



Degree of Heat Necessary. 



A temperature of 118° F. to 125° F. in all parts of the mill is suffi- 

 cient to kill mill pests. To obtain these killing temperatures in the 

 least exposed parts, it is necessary to heat other portions to a still 

 higher temperature unless greater care than usual is taken to dis- 

 tribute radiation surfaces according to the situation. For tempera- 

 tures secured in various parts of mills heated experimentally with 

 equipments already installed, see data in Tables I to XII. 



Use of Steam Heat. 



Steam heat is the most satisfactory heat for raising mill tempera- 

 tures to the killing point. A pressure of 25 to 50 pounds is recom- 

 mended. 



Amount of Radiation Required. 



The number of square feet of radiation required to heat a given 

 number of cubic feet of space depends upon the number of doors and 

 windows in a building and upon the general tightness of the structure. 

 Because these factors vary so greatly in mills, a definite recommen- 

 dation for amount of radiation surface can not be given. The engi- 



* Goodwin, W. H., flour mill fumigation. Bui. Ohio Agr. Exp. Sta., no. 234, p. 184, 

 January, 1912. 



