CHAPTER V. 



INFLUENCE OF SPRAYS ON THE VEGETATION OF THE TREES. 



SAVING or FOLlA(iE FROM INJURY BY CURL. 



(PI. VII.) 



The effectiveness of the winter sprays discussed in the previous chap- 

 ter in saving the foliage of peach trees from injury hy peach leaf curl 

 has been carefully considered. The relative importance of this matter 

 appears from the fact that it is the injury from the loss of foliage which 

 is responsilile for the ultimat(> loss of the fruit. The spray work 

 already mentioned was compii'ted, in 18!>5, about the close of the first 

 week in March. From this time on the flowers opened rapidly, and 

 they were soon followed by the pushing of the leaf buds and the com- 

 plete resumption of the vegetative growth of the year. By the mid- 

 dle of April the trees were well in foliage, while peach leaf curl was 

 nearing the height of its development. By the 22d of the month 

 the contrast between healthy and diseased foliage on the sprayed and 

 unsprayed trees had become so great that a careful estimate was made 

 of the percentage of the diseased leaves upon every tree in the block. 

 The first estimate of the condition of the foliage was made to deter- 

 mine the amount and percentage of disease present on sprayed and 

 unsprayed trees. The estimate of each tree was calculated upon the 

 basis that the foliage present represented 100 per cent, and the amount 

 of badly diseased leaves was taken as a certain per cent of the leaves 

 present at that date. Badly diseased leaves w;ere considered as those 

 seeming to have sufficient curl present to cause their premature fall 

 from the tree. The ultimate comparisons of sprayed with unsprayed 

 rows are not based upon this first estimate of foliage as the disease was 

 still progressing. The parasite was still in the vegetative state, few of 

 the swollen leaves as yet showing the fruit of the fungus, and still fewer 

 having- fallen from the trees. The trees spraved with the stronger 

 sulphur preparations were injured somewhat by the sprays, many of 

 the more tender twigs being killed. This delayed the leafing of these 

 trees, and resulted in their showing rather a smaller percentage of 

 diseased foliage at the time this estimate was made than would have 

 been the case had the leaves pushed earlier. These discrepancies 

 influence only a few of the sprayed rows. In other respects, it is 

 believed the numerous influencing conditions would apply, so far as 



could be told, with equal force to all rows. 



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