CHAPTER XL 

 DISEASES OF TREES AND VINES 



A few suggestions concerning pathological conditions which arise 

 in trees and vines and prescription of treatment and remedies may be 

 helpful: First, diseases demonstrated to be caused by fungi and bac- 

 teria ; second, abnormal conditions, of which the causes are not yet clear. 



Powdery Mildews. Fungi which bring upon the leaf surface the 

 appearance of a whitish powder and afterwards cause the leaf to curl 

 and dry without producing marked swelling, perforation or discolora- 

 tion, can be checked by the use of sulphur. The chief of these is the 

 mildew of the grape, the mildew of the apple, appearing chiefly on 

 the young growth, etc. The way to use sulphur for vine mildew is to 

 freely apply finely ground or sublimed sulphur on the young foliage at 

 the first sign of the trouble, or before it appears in regions where it 

 may always be expected, either by hand or with suitable machinery 

 which is fully discussed in Bulletin 186 of the California Experiment 

 Station. Apple mildew is treated by spraying with iron sulphide added 

 to the poison used for the codlin moth, as described in the preceding 

 chapter. 



Leaf-Spotting, Puncturing or Deforming Fungi. These classes 

 are usually distinguishable by the results they produce. The mildew 

 of the peach produces dense, whitish patches on the leaves and grow- 

 ing fruit; the curl-leaf fungus of the peach produces swellings and 

 contortions of the leaf; the scab of the apple and pear produces first 

 a smoky appearance on the leaf and afterwards causes black scabby 

 patches on the fruit and on the young twigs ; the slot-hole fungus of 

 the apricot, plum, cherry, and almond cuts roundish holes in the leaves 

 as though a shotgun had been discharged through the foliage, and 

 then, in the case of the apricot, produces roundish, dark red pustules 

 on the fruit ; the brown rot which attacks both twigs and fruit of apri- 

 cots, prune, blackberry, etc., produced eruptions on plums and peaches ; 

 the rust fungi of the under sides of the leaves, first of a yellowish or 

 orange color, changing to dark brown or black, and causing the leaf 

 to fall. These fungi are only slightly, if at all, checked by the dry 

 sulphur treatment, and are best subdued by the use of copper solutions : 



The Bordeaux Mixture. Lime, four pounds; bluestone (sulphate of copper), 

 four pounds ; water, forty gallons. Use part of the water to slake the lime and 

 dissolve the bluestone, which should be done in separate vessels. The bluestone 

 should not be put in a metal vessel. If put into a bag and suspended near the 

 surface of the water, it will dissolve more readily, or hot water may be used 

 in making the solution. Both should be cold when mixed, and the resultant 

 mixture will be a beautiful blue wash. If mixed hot, a black compound (copper 

 oxide) is produced, which reduces the value of the wash. After thorough 

 mixing of the solution, water should be added to bring the bulk up to forty 

 gallons. 



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