RED SPIDER AND POWDERY MILDEW 



289 



JBBL 



Fig. 1. A satisfactory type of hygrometer. 



the sale of insecticides and fiinaicides. The choice of any of the materials 

 mentioned should be go\erned by the retail cost. 



The proper ciioice of equipment for dusting is important. The duster 

 illustrated in Figure 2 has proved most satisfactory for greenhouse purposes. 

 Its use among the plants is not hindered by wires, posts, trellises, or deep 

 walks as is the use of the heavier dusters strapped to the body and provided 

 with long extension tubes. This duster holds 2 quarts or 4 pounds of dust so 

 that the load carried is very light. The dust is expelled by pushing a plunger 



