FIELD EXPERIMKNTS. 43 



to find all of these conditions. The most important thing is to 

 spray the plants when they are of the proper size, before they 

 get too large. 



It is to be hoped that the growers of small grains that are 

 troubled with "charlock" (whether it be wild mmstard, wild 

 radish or wild turnip) will keep this matter in mind and pro- 

 vide a supply of iron sulphate. The materials must be provided 

 amply in advance; a day or two days delay may make all the 

 diiTerence in the world with the results of the application. The 

 materials are applied with an ordinary spray pumip, such as is 

 used in spraying potatoes. A fine nozzle must be used and the 

 pressure to 60 to 80 pounds to the square inch in order to 

 develop a fine mist. Sprinkling the plants will not kill them. 

 The material must fall upon the plants in the form of a fine 

 mist and the spraying should be done after the dew has dried 

 from the plants, and best on a bright day when there is no 

 wind. Application must be m.ade before the plants have de- 

 veloped beyond the fourth leaf. At this stage the plant is 

 so small that it can be covered by an ordinary drinking tumbler. 



Condensed Directions. Dissolve 100 pounds iron sulphate in 

 70 gallons of water, or 70 in 50 gallons, as is most convenient. 

 Apply at the rate of about 70 gallons per acre. Use a power- 

 ful pump and have the pressure at least 60 pounds. Use a fine 

 nozzle. This should develop a fine dust-like mist. A coarse 

 mist will not do. Spray after the dew has dried oft when the 

 plants are in the fourth leaf. Choose if possible a bright, warm 

 day without wind. But ^pray when the plants are the proper 

 size even if the day is not all that could be desired. If the field 

 is badly infested or the conditions of the first spraying were 

 not satisfactor}^ a second spraying three days later is desirable. 

 Later go over the field and- pull by hand any plants that may 

 have escaped. 



Effect of Iron Sulphate Spray Upon Potatoes. 



Because of urging growers to spray for wild mustard in oats, 

 the writer was in the spring of 1913 the recipient of quite a 

 number of letters of inquiry as to w^hether wdld mustard could 

 not be controlled in potatoes by spraying with sulphate of iron 

 solution. The reply was sent that the treatment would kill 



