Dry Spraying of Charlock. 



141 



for ten days or a fortnight after the application, and for that 

 reason only the notes made on the second examination on 

 June 30th are given here. These were as follows: — 



Plot 1. Sulphate of Copper — 40 lb. per acre ) 



o . , r The whole of the Charlock 



»i ™« n »»• jj » h n " 



plants bad been destroyed. Even the large seed pods were 



dead and shrivelled, and the plants looked like dead sticks. 

 „ 3. Sulphate of Copper — 20 lb. per acre. All the leaves and flowere 



were dead, and the great majority of the seed pods were too 



badly shrivelled to ripen seed. 

 „ 4. Sulphate of Copper — 10 lb. per acre. 75 per cent, of leaves and 



flowers were dead, and much damage had been done to the 



seed pods. 



„ 5. Sulphate of Iron — 50 lb. per acre. 50 per cent, of leaves and 

 flowers were dead, but the seed pods were very little injured. 



A week later, bunches of the Charlock plants pulled at random 

 from the respective plots were photographed, and those from 

 Plots 1, 3 and 5 together with a bunch from the untreated 

 part of the field are shown in the illustration. The flowers at 

 this time had disappeared, but seed pods on the specimens 

 gathered from the untreated part of the field and from Plot 5 

 may be easily seen. As regards the crop, the Rye, although 

 slightly yellowed at first, showed no permanent injury on any 

 of the plots, but the Vetches were rather badly damaged, 

 particularly on Plots 1, '2, and 3. 



It should be mentioned that in dry spraying with a Knapsack 

 machine it was found necessary for the operators to wear 

 respirators, since the fine dust of the sulphate of copper spray 

 tended to produce nausea. A simple respirator made of two or 

 three thicknesses of gauze was found to give complete protection. 

 It is very possible, however, that this precaution would be un- 

 necessary in the case of a horse-drawn machine, where the 

 operator is seated at some distance from the spraying nozzles. 



Conclusions. — (1) The success in dry spraying for Charlock 

 lies in the choice of a suitable day for the operation. The weather 

 should be fairly settled, and there should be a heavy dew and 

 no wind at the time of application. Provided these conditions 

 prevail, we may say confidently that dry spraying is quite as 

 effective as wet spraying. 



(2) Of the substances tested, nitrolim was found to be of no 

 value, sulphate of iron was effective only in quantities, which, 

 on the ground of cost, make it impracticable, but sulphate of 

 copper gave excellent results. 



