10 July, 1917. J Anthracnose or Black Spot of the Vine. 419 



solution is complete. lu this case the usual precaution of pouring in 

 a thin stream, with constant stirring, must be taken, so as to avoid 

 dangerous splashes, which are not to be feared with the first method 

 of preparation. 



It is well at this stage to warn growers against placing any reliance 

 in copper sulphate solution, Bordeaux mixture, &c., as a winter swab; 

 as shown above, these are quite useless against the fungus in its resting 

 stages. The addition of copper sulphate to the winter swab has also 

 been recommended. It can do no good, and is merely a waste of copper 

 sulphate, which is very expensive at present. 



The same may be said of lime-sulphur solution, used successfully by 

 orchardists to combat other fungi, and sometimes recommended for 

 Black Spot. It may possibly prove of use, as Bordeaux mixture does, 

 for summer treatment, thougli it has not yet been properly tested. As 

 a winter swab it has no value, since it can have no action on the very 

 resistant sclerotia which only yield to a corrosive apjilication. 



When to Swab. 



The best time is as near the bursting of the buds in spring as pos- 

 &ible. Unfortunately, the exact date of this cannot be forecasted 

 exactly; tiie season may be a week or so early or late. If too long 

 delayed, there is danger of being surprised by early sprouting, and once 

 the buds start growth swabbing must be discontinued, as it would cor- 

 rode and destroy any growing tissues. 



The efficacy of a double swab, with a fortnight's interval between 

 each application, has been refen-ed to. A safe method is to swab three 

 or four weeks before sprouting is expected, the apiplication being re- 

 peated on the worst affected patches just before the buds break. 



One effect of the swab is to retard sprouting, sometimes by even as 

 much as a fortnight. In districts liable to spring frosts, this delay 

 may be a distinct advantage; it has sometimes meant the saving of the 

 crop. The appearance of the vines after treatment is curious, and to 

 some extent alarming, a& they are blackened and discoloured; no 

 damage, however, need be feared with the formula given above, pro- 

 vided the buds have not commenced to move. The first growth of 

 treated vines is usuallv apt to cause anxiety ; the young shoots at first 

 appear to be sickly and to make poor growth. This is, however, only 

 tem,poraiy, and development soon becomes normal. After a short time 

 treated vines will be found to' make more vigorous growth than un- 

 treated ones. 



Early swabbing is not recommended ; in midwinter the sclerotia seem 

 more resistant than in very early spring. It is well to swab trellised 

 vines before the rods are tied down, in order to spare the wires as 

 much aa possible from damage by the corrosive solution. 



Late sprouting also favours varieties liable to faulty setting at blos- 

 som, such as Malbeck. A delay of a week may mean striking more 

 favorable weather for this important function. The swab al-o destroys 

 several animal pests such as scale insects, Erinose, &c. ; it is, however, 

 quite useless against the wintering forn s of Oidiuui and DoAny 

 Mildew, notwithstanding opinions sometimes expressed to the contrary. 

 Zacharewicz states that it prevents Crown-gall (Broussin). 



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