CHAPTER XIX. 



FUNGUS DISEASES OF PLANTS. 



HOW TO PREVENT AND CURE THEM. 

 " An ounce of prevention is better than a pound of cure." 



ECENT investigations have acquainted us pretty 

 well with the true nature, modes of propagation, 

 etc., of most of the fungi which attack and 

 damage many of our garden crops, and cause the 

 various rots, blights and mildews. Among them 

 we have the potato rot, the tomato rot, the celery 

 blight, the bean rust, the strawberry rust, the 

 lettuce mildew, the melon vine disease, etc. 

 Heat ancf moisture favor the germination of the spores of these 

 fungi, and consequently the diseases generally develop on hot 

 days after rains, or during damp sultry weather. Unfortunately 

 there is hardly a cure for any of them yet suggested. The only 

 safety for the gardener, in this matter, lies in prevention, and here 

 again, as in the case of insects, we must look to change of loca- 

 tion planting at the greatest possible distance from any ground 

 where the same vegetable was grown before, as to the first 

 feasible preventive measure to be adopted. Even this, as in the 

 analogous case of insects, is not an absolute protection, and the 

 great difficulty here is that we have no means to anticipate an 

 attack of such diseases with any degree of certainty. 



In all localities where diseases of this character are prevail- 

 ing to some extent, we may generally expect them late in July 

 or August, when hot weather is following after warm rains, and 

 here prudence would dictate the use of precautionary measures. 

 The trouble again is that so little definite information on the most 

 effective germicides, and the most convenient mode of application 

 is yet developed, and I will have to content myself with merely 

 making suggestions. 



SULPHATE OF COPPER. This salt (blue vitriol or blue 

 stone), in simple solution or in various compounds, has just been 

 recognized as a preventive of the dreaded mildew and black rot 

 in grapes, and also shown its efficacy in destroying the vitality 

 of other fungus spores. It must be remembered, however, that 

 this kills the germs and prevents their starting into life, but has 

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