288 STATE HORTICULTURAL SOCIETY. 



Of probability that a germ or anything of kindred nature should remain dor- 

 mant in a tree fifteen or twenty years, that tree meanwhile being taxed to its 

 utmost in the production of fruit, and often exhausted and injured by over 

 production. 



There can be no reasonable doubt that in orchards over five years old the 

 disease is due to some unknown local influence, and not to anything on or in 

 the trees when procured from the nursery. I am the more inclined to this 

 view from the fact that when symptoms of yellows are once manifest in any 

 branch the whole tree becomes involved in a comparatively short time ; i. e. 

 within one or two years. In other words, the disease is virulent, and does 

 not remain dormant in one branch very long after it has appeard in another. 



INJURIES BY MEN OR QUADRUPEDS. 



A belief, current in some parts of the country, attributes yellows to any 

 severe injury of trunk or roots, such as might be made by careless cultivation, 

 or by rabbits, mic^, etc. This belief arose, no doubt, from confounding a 

 yellow appearance of the foliage with genuine yellows. These injuries are 

 all on a par with those inflicted by the peach tree borer, and what I shall say 

 about the latter will apply to these also. 



INJURY BY BORERS. 



Tho larva? of ^Egeria devour the inner bark of the peach, usually at or just 

 beneath the earth's surface, often entirely girdling the tree. This insect is 

 much more common than Scolytus, which I have not observed upon healthy 

 trees, and is the only one worth mentioning in this connection. 



Borers are so common and so destructive to the peach tree, and have so 

 frequently been aecueed of causing yellows, that, while I had no faith what- 

 ever, I nevertheless gave particular attention to this theory both in 1887 and 

 1888. My observations show clearly that while they kill or seriously injure 

 many trees, especially on sandy soil, they have nothing whatever to do with 

 the yellows. Some of my reasons for this conclusion are as follows: 



1. Borers have been prevalent for many years, and often very destructive 

 in localities where yellows has never appeared; e.g., Washtenaw county, 

 Mich. ; Accomac county, Ya. ; Sussex county, Del. 



2. Borers are much more prevalent on sandy soil than on heavy loam or 

 clay. But yellows is equally destructive on the latter. I observed this fact 

 repeatedly in Maryland and Delaware. Those owning orchards on sand are 

 obliged to search for borers once or twice each year. Those whose orchards 

 are on clay often neglect to " worm" their trees for several years together 

 without evil results. 



3. In 1887, in orchard No. 6 of this report, T found the collars and crowns 

 of many trees had never been injured in the least either by borers OT by 

 bruises of any sort ; yet these trees were suffering from yellows. The earth 

 had beeu dug away from about one thousand trunks on the east side of the 

 orchard, preparatory to the annual search for borers, but so few were found, 

 that it was not thought worth while to examine further. Almost the only 

 injuries I saw were small hacks made in removing the earth. Moreover, the 

 foliage of the orchard nowhere gave any evidence of borers, and I was in- 

 formed that this insect had never been troublesome. Notwithstanding this 



