36 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



(luring sunsliine, under the supposition that it will scald the foliage 

 iuul destroy the plants. 



It is true that the sun is a factor in causing the scalded and scorched 

 ;il>pearance of the leaves of the grape, but it is only where the tissue 

 lia.s been destroyed by mildew that the action of the sun dries up tbe 

 diseased portion, and where mildew is not present, the action of suu- 

 .shine shows no injury whatever, even upon the healthy part of an 

 injured leaf. 



Tbe delay to recognize the true cause of failure with many varieties 

 of grapes in dilierent sections of the country has had a disastrous 

 ciiiecfc upon the general introduction and extension of their culture. It 

 lif'tS also led to heavy losses by individuals who have been induced to 

 })archaso costly varieties which they could not succeed in growing, on 

 account of climatic conditions which they could not control. It is 

 well known that all varieties of grapes which are particularly sensitive 

 to tbe climatic iuflaences which promote the growth of mildew have little 

 or no value for general cultivation, no matter how high the quality of 

 their fruit may rank; but by far too little notice is taken of this par- 

 ticular by those who are introducing new varieties. If a variety is 

 found to be of superior quality in one locality, it is extended under the 

 supposition that it will prove equally valuable in all other localities ; 

 and if failures occur, as they so often do, they are freely attributed to 

 bad or improper treatment on the part of the grower, and he will be 

 blamed for neglect of some non-essential, which in future he secures, 

 with no better result, and the industry is abandoned. The fact is 

 strangely overlooked that, in special favorable grape-growing locali- 

 ties, an abundance of fruit is annually produced, even when all pro- 

 nounced essentials to success are mostly wholly ignored. 



When it was ascertained that the mildew of most frequent occurrence 

 and of the most malignant character on native grapes was caused by 

 an excess of moisture on the foliage, chiefly because of its subjection 

 to continued heavy dews, it soon became evident that such localities as 

 had become renowned for continued successful grape culture, and where 

 all varieties did equally well, were those where hearj' dews were of the 

 least frequent occurrence. 



Microscopical investigations in regard to the diseases of plftnts are of 

 comparatively recent date, and the deductions which have been made 

 from them by microscopists are, to a certain extent, crude, owing to 

 their want of practical knowledge in regard to vegetable poysiology 

 and the varied phenomena relating to cause and effect which are known 

 to the experienced and observant cultivator. 



Several years ago a microscopist assured grape-growers that the 

 destruction of foliage caused by mildew was harmless, if not, indeed, 

 beneficial, inasmuch as it permitted the sunlight more readily to act 

 ti[)on the fruit, and thereby assisted and hastened the ripening process. 

 ."Such a suggestion displayed ignorance of the value of leaves to plants. 

 A slight reflection would have shown that if such results followed mil- 

 dewed grape-vines, complaints from growers would not exist. More 

 1 ecently it has been advised to remove and destroy by burning all the 

 foliage which falls from vines injured by mildew, in order to prevent 

 tlic resting spores of the fungus from attacking future growths, and 

 th^as stamp out the disease. As a matter of fact, the burning of the 

 leaves would certainly destroy any resting spores attached to them, 

 but this would not therefore prevent similar attacks in the future 

 whenever the climatic conditions i)roved conducive to the introduction 

 und growth of the fungus. 



