CHAPTER XLIII. 



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 bacteria ; 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 dis- 

 coloration, 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. For vine mildew freely apply 

 finely ground or sublimed sulphur on the young foliage at the first 

 sign of the trouble. Apple mildew is treated by removing all dis- 

 torted twigs at pruning. 



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 apricots, prune, blackberry, etc., produces 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 the Bordeaux mixture as follows : 



Bluestone, 16 pounds; quicklime, 20 pounds; water, 200 gallons. 

 Dissolve the bluestone and slake the lime in separate vats. Thoroughly 

 e dissolved bluestone with one-half the water, and the slaked lime 

 with the other half. Run the two mixtures together in a single stream 

 ito the spray tank through a fine screen. For convenience the mixing 

 vats may be placed on an elevated platform, and the two parts mixed as 

 r are flowing into the spray tank. The milk of lime should be con- 

 tinuously stirred during the mixing. 



This is safe to use on foliage. In the case of the peach blight, 

 ch is an invasion of the young bark by the shot-hole fungus, an 



!^ P ubli <f tion on P lant diseases, reviewing comprehensively existing 

 ^^ treatment Circular 227 of the University 



