PEACH YELLOWS. ^ 379 



appear first in bottoms and rich places. This coincides with my observa- 

 tions. 



The effect of moist spots, as well as of excessive rains, has been ascribed to 

 the dilution of mineral constituents in the earth fluids, whereby the tree 

 starves in the midst of plenty. Another explanation is that root-fungi and 

 various micro-organisms thrive better in such situations I have at present no 

 theory to offer. 



NEGLECT Of CULTIVATION. 



This was once a favorite explanation of the disease, particularly with writers 

 who never went abroad, but evolved truth from their inner consciousness. In 

 recent years, however, I have heard it asserted that trees left in sod and other- 

 wise maltreated where the only ones free from disease. There is no truth in 

 either assertion, or rather each is only a half truth. Many orchards in Mary- 

 land and Delaware are kept entirely free from grass and weeds and are cul- 

 tivated more thoroughly than the corn fields; but cultivation from early 

 spring to middle summer, or even all the year round, has not been able to 

 prevent the appearance of yellows, or to hold it in check. Many orchards 

 which have received the utmost attention have become badly diseased. On 

 the other hand, neglected orchards are by no means free from the disease. I 

 have seen it in a number of such orchards; e. g.y in 1887, at Still Pond, Md., 

 in a small old orchard owned by J. Frank Wilson. This had been in sod and 

 used for a sheep pasture four years, but contained quite a number of recently 

 diseased trees. Again, in 1888, on the farm of G. M. Eldridge, near Cecilton, 

 Md., I saw many diseased trees in an old orchard used as a pasture. This 

 orchard has been plowed only once in six years, and that was some time ago. 

 The diseased also occurs frequently on lawns and grass plots never plowed or 

 otherwise disturbed, and I have moreover seen it in trees on soil entirely free 

 from vegetation and packed hard by the daily tread of many feet. 



NEGLECT OF PRUNING. • 



This was a favorite theory with A. J. Downing. He advised the shorten- 

 ing in of the bearing wood one-half every spring. If the trees came from an 

 originally healthy stock he believed this would keep them healthy. There is, 

 however, no good reason for believing it would. S. H. Wilson, of Baltimore 

 county, Md., claims to have tried it faithfully with no success. I can not 

 from my own observation furnish any testimony on this point. 



EXCESSIVE USE OF NITROGENOUS MANURES. 



The belief that the spread of yellows is favored by the use of animal 

 manures is quite prevalent, and appears to have some basis in fact. One of 

 Dr. Henry Kidgely's orchards which blighted most rapidly with yellows was 

 very highly manured. The McDaniel orchard was also twice very heavily 

 manured soon after being set. The Price orchards Nos. 2 and 3 of this 

 report, have also been freely and repeatedly manured. In particular a nar- 

 row strip, of perhaps one-half acre, on the northeast side of No. 2, which 

 contains some stones and was believed to be less fertile, received great quan- 

 tities of dung, and there I found nearly every tree diseased by yellows. 



