20 



Eradication of Charlock. 



horse distributor; and generally it will be found that more 

 than this quantity is required ; but if it is put on with a hand- 

 spraying machine a larger quantity is required, and it is safer 

 to spray at the rate of 40 or 50 gallons per acre, even if the 

 strength of the solution is slightly decreased. Horse dis- 

 tributors spray more evenly and regularly than hand 

 sprayers. 



The solution should be applied in fine weather, when there 

 is no prospect of early rain, and it is important to spray before 

 the charlock and the plants among which it is growing are 

 high. The best period to kill charlock is when it is in 

 " rough leaf." When the corn is high the spray cannot 

 reach all the charlock growing among the plants ; and a 

 much larger quantity of a stronger solution is required when 

 the charlock is high and in flower than when it is two or 

 three inches high. Two applications of the dressing are 

 recommended, at short intervals. 



In experiments made on the 8th of June last, upon char- 

 lock in full flower among oats 18 inches high, it was found 

 that a four per cent, solution, that is four pounds of sulphate 

 of copper to every ten gallons of water, applied at the rate 

 of slightly over 50 gallons per acre, did not kill all the flowers. 

 The leaves, being protected to a great extent by the corn 

 plants, were also not sufficiently injured to affect the charlock 

 materially ; at the same time the corn plants showed no sign 

 of injury. A six per cent, solution did not quite kill all the 

 flowers, and hurt the blades of the corn plants in some degree. 



The greatest care must be taken as to the purity of the 

 sulphate of copper used. It should be accurately weighed, 

 and the solution must be kept well stirred. 



Sulphate of copper acts upon charlock because the leaves 

 of this plant are rough, and consequently the solution 

 remains upon them and burns them. The leaves of corn 

 plants are smooth and stand erect so that the solution runs 

 off them. The texture of their leaves is much closer than 

 those of charlock ; the leaves of tares and mangels are also 

 smoother than those of charlock. Again, the leaves of the 

 latter plant have comparatively deep furrows by the sides 

 of their midribs and veins in which the solutions settle, 



