592 Journal of Agriculture, Victoria. [10 Oct., 1918. 



COPPER FUNGICIDES FOR VINE DISEASES. 



By F. de Castella, Government Viticulturist. 



Fungicides are either preventive or curative. The latter can onlj' 

 be used with success for the control of fungi, the mycelium of which is 

 external to the tissues of the plant, such as Oidium, or Powdery Mildew 

 of the vine {Uncinula spiralis), against w^liich sulphur dustings are the 

 standard remedy, whilst spraying with weak solutions of potash per- 

 manganate, liver of sulphur, &c., give good results in colder weather. In 

 the case of most fungi, and more particularly Downy Mildew and Black 

 Spot of the vine, the mycelium develops in the interior of the tissues 

 of the plant. These can only be controlled by preventive treatment; 

 the entry of tlhe fungus into the tissue of the plant must be rendered Im- 

 possible by spraying with some fungus poison in such quantity that 

 every rain or dew drop may dissolve sufficient of it to prevent the ger- 

 mination of any fungus spore which may fall into it. In other words, 

 prevention of spore germination protects the tissues of the vine from 

 infection. 



Many fungus poisons have been suggested, among which silver, mer- 

 cury, cadmium, and alkaline polysulphides (lime-sulphur, &c.) naay be 

 mentioned; but copper has so far proved the most efficacious, and is 

 to-day by far the most widely used of preventive fungicides. Copper 

 may be employed for this purpose in various forms, each of which has 

 its advocates; the oldest copper fungicide is undoubtedly Bordeaux Mix- 

 ture or Copper-Lime, which is still the best known and most widely used. 

 It is, therefore, the form which must first be considered; subsequently, 

 some of the substitutes which from time to time have been proposed, and 

 more or less extensively used, will be described. The most important 

 of these is copper-soda or Burgundy Mixture, which is well known to 

 most of our orchardists and potato-growers. Though an excellent fungi- 

 cide, present-day difficulties in the way of procuring the carbonate of 

 soda necessary for its preparation deprive it of much of its importance. 

 In spite of its undoubted qualities, it is in no wise superior to Bordeaux 

 Mixture; there are, indeed, sound reasons for preferring the latter, as 

 will be shown subsequently.* 



Bordeaux Mixture. 



The origin of this standard fungicide may be briefly stated. In 

 many vineyards in the Bordeaux district of France, where fences or 

 walls are often absent, it has long been customary to sprinkle the outer 

 rows fringing the roads with a mixture of lime and bluestone, in order 

 to protect the fruit from marauders. The resultant pale blue markings 

 of the foliage serving the same purpose as a notice " Poison laid here." 

 When Downy Mildew first ravaged the vineyards of France in the early 

 eighties of last century, it was soon noticed that these outer rows suffered 

 far less from the disease than vines which were not so treated. Thus 

 was discovered, quite accidentally, the efficacy of copper for the control 

 of Mildew and otlher fungi. 



• The main reasons for preferring ' ' Bordeaux " are that it adheres better, is less depressing on 

 vegetation and burns the foliage less. It also deteriorates much less rapidly after a;>ixing. In warm 

 VI eather the precipitate of copper-soda soon becomes granular an d loses its power of adherence. 



