DISEASES OF CULTIVATED PLANTS 497 



outer ones still retain their leaves. In nearly all such instances, 

 however, the leaves of the living parts show indications of disease. 

 Sometimes the plants die before the leaves unfold, so that the un- 

 opened flower and leaf buds may be seen upon the dead branches. 

 In the worst cases, where all the canes are dead, the roots also die. 

 Occasional instances were noted where fresh sprouts had been sent 

 up around the base of the diseased canes. 



The only positive remedy that can be suggested is the removal 

 of the whole plant as soon as the disease begins to be manifested in 

 the yellow foliage and prematurely colored fruits. The diseased 

 plants should be burned, as the spores and conidia may be produced 

 in abundance on dead plants and the trouble communicated to 

 living bushes. (N. Y. [Ithaca] E. S. B. 125.) 



Mildew (See page 491). 



DISEASES OP GRAPES. 



Black Rot. This is the most generally distributed and de- 

 structive fungous disease of the grape in the region east of the Rocky 

 Mountains. It is caused by a parasitic fungus known as Guignardia 

 bidwellii. It gains entrance to the plant by means of minute germs 

 called spores. These are borne in small black spore cases, and can 

 not bo seen with the naked eye. They are distributed chiefly by the 

 wind and rain. When these spores come in contact with the young 

 and tender parts of the vine, under favorable conditions, they germ- 

 inate and produce a slender tube, which penetrates the tissue and 

 may destroy it. 



This disease attacks the leaves and shoots, as well as the fruit. 

 It usually makes its first appearance on the leaves and young 

 shoots, producing reddish-brown dead spots. The fruit may be at- 

 tacked when young, but usually the disease does not attract attention 

 until the berries are half grown or more. Brown or blackish spots 

 first appear ; these spread and soon affect the whole berry, which be- 

 comes black and shriveled. These diseased berries remain attached 

 to the vine, and their surfaces become covered with minute black 

 pustules, which contain the summer spores of the fungus. During 

 the winter and spring another form, called the winter, or resting 

 spore, is produced upon these old, shriveled berries. These spores 

 help to carry the disease over from one season to another. This fact 

 would indicate the desirability of destroying, by burning, all dis- 

 eased fruit, as well as leaves and prunings, as early in the spring as 

 possible. 



This disease can be effectually controlled by thorough spraying 

 with Bordeaux mixture. Five or six applications are usually neces- 

 sary during the season, the first being made just before the buds 

 open. For the last one or two applications, some fungicide which 

 does not stain the fruit should be used. Burgundy mixture is rec- 

 ommended for this purpose. Full directions regarding the prepara- 

 tion of the fungicides and the times of application will be found 

 later. 



Covering the bunches of grapes with paper bags soon after the 

 Blossoms fall is a means of preventing black-rot and most other 



