DISEASES OF CULTIVATED PLANTS 589 



Ions. This stock solution is preserved in tightly corked jugs and 

 must be shaken well before being used. 



The seed wheat is treated with sar solution as follows: either 

 1 quart of the solution is diluted with 50 gallons of water and the 

 grain soaked therein for about twelve hours, or else a strong solu- 

 tion (1 gallon of the stock to 50 gallons of water) is used and the 

 grain soaked only two hours. In either case the grain must be stirred 

 several times during the treatment and spread out to dry after- 

 wards. If the grain contains much smut it should first be washed 

 with water in order to skim off the smut balls before it is put in the 

 sar solution to soak. 



The Loose Smuts of Wheat and Barley. The loose smuts of 

 wheat and barley are similar to each other and consequently require 

 similar treatments. They destroy practically the entire head, chang- 

 ing kernels and glumes to a mass of odorless black spores. These are 

 blown about by the wind at the flowering time 01 these crops and 

 infect the young sound kernels. In this way these diseases are car- 

 ried over from one year to the next. 



The formalin treatment as recommended in this circular for 

 other smuts of wheat and oats can not be used with success to pre- 

 vent the loose smuts of wheat and barley ; nor is the copper sulphate 

 method, or the Jensen hot water treatment successful. A modified 

 hot water treatment has been tried with some success and is recom- 

 mended in a recent bulletin of the U. S. Department of Agriculture, 

 Bureau of Plant Industry (Bulletin No. 152). This method deserves 

 a fair trial, especially since these smuts are sources of heavy losses 

 with these crops and very difficult otherwise to prevent. It is hoped 

 that this modified hot water treatment will prove efficient and prac- 

 ticable. Briefly the treatment recommended, as given in the sum- 

 mary of the above cited publication, is as follows: For barley, a 

 soaking in cold water for five hours, followed by a soaking in hot 

 water for fifteen minutes at a temperature of 52 C. (125.6 F.) ; 

 for wheat, a soaking in cold water for five hours, followed by a soak- 

 ing in hot water for ten minutes at a temperature of 54 C. (129.2 

 F.). (See that bulletin for further details of the process.) (Ind. 

 E. S. Cir. 22.) 



Powdery Mildew of Wheat. The powdery mildew of wheat 

 may be recognized by the white or greyish mould which appears on 

 the surface of the leaves or among the glumes of the fruiting head. 

 It is found to be most serious in damp spots in the field, or in pro- 

 tected or shaded localities. In a field bounded on the east side by 

 timber land it was very abundant, particularly along the edge of the 

 woods. It was also found abundant wherever the wheat is of 

 particularly rank growth. 



This disease is caused by a parasitic fungus, the mycelium of 

 which grows on the surface of the wheat plant, sending feeding 

 branches into the surface cells of the host and absorbing its juices. 

 It reproduces itself during the summer by the production of chains 

 of colorless spores which are cut off successively from upright threads 

 of the surface mycelium. These spores serve to spread the fungus 



