26 PEACH LEAF CUKL: ITS W^ATURE AKD TREATMENT. 



the curl leaf in the peach and nectarine trees was worse than it had 

 ever been before, the Malta being- the only variety that was entirely 

 healthy on level land. The varieties received from England and 

 planted on the level land were just as badly affected as the others. 

 The first and second l)ench orchards suffered alike with those on the 

 level ground, ])ut the orchard highest up, at an elevation of 800 feet, 

 had no curl in any case, and the trees appeared to have suffered less 

 from cold than those lower down (1. c, p. 342). Mr. Sharpe says 

 that in 1890, "as heretofore, the trees on the upper Ijenches, both 

 nectarine and peach, escaped the curl leaf entirely" (1. c, p. 449). 

 Again, it is said that "the peach crop on the level land this 3^ear [in 

 1898] was almost an entire failure. The curl leaf was very prevalent, 

 nearly every tree being seriously affected by it." Kelating to the 

 orchard on the bench lands, it is stated that "curl leaf did not affect 

 the foliage there; in fact, it has never injured the foliage on either 

 peach or nectarine trees on the benches over 300 feet above the 

 valley" (1. c, p. 403). These facts have an especial interest and 

 value in that they were recorded by a single observer on one farm 

 and during successive years and epidemics of curl, and they are in 

 perfect harmony with the experience of a majority of the growers 

 whose views are presented above. 



The soil may exert its influence l)y abundantly or feebly supplying 

 the transpiration stream, in accordance with the degree of accessibility 

 of the moisture it contains, to the root hairs of the tree. It may be 

 said, however, that as leaf curl commonly develops at the beginning 

 of spring growth or at the close of the winter's rains, the soil will 

 rarely be found so deficient in moisture as to greatl}^ retard the devel- 

 opment of the disease where other conditions are f aA'orable. It is prob- 

 ably equally true that the excess of water usually found in the soil 

 in the spring is favorable to the special development of the disease at 

 that season in its worst form. 



Besides the influence of temporary excessive humidity of the atmos- 

 phere upon leaf curl, which has already been considered, there are 

 other atmospheric influences and relations of importance, which depend 

 upon the local or general geographic, topographic, and climatic fea- 

 tures of country. Some of these more prominent atmospheric 

 influences may here be briefly considered, together with their most 

 probable causes. 



Proximity to large bodies of water, whether salt or fresh, greatly 

 favors the development of curl. The cause for this clearly rests in the 

 resulting greater humidity and lower temperature of the atmosphere. 

 Plants growing in a constantly humid atmosphere have normally more 

 succulent and tender tissues than those growing in a drier region. The 

 reasons for this have already been alluded to for special cases of 

 extreme atmospheric humidity and lowered temperature. Near large 



