280 Appendix. 



HISTORICAL. 



Though this trouble has been known as working havoc in orchards for a 

 century or more, it is only in comparatively recent times that its true nature has 

 been well understood. For a long period of years the discussions of this trouble 

 were of such a theoretic nature, that many horticultural societies forbade its 

 being brought up in their meetings, unless some one had something of absolute 

 knowledge to offer about it. Various causes were ascribed for its presence, such 

 as "sour sap," "atmospheric conditions," "soil conditions," and "effects of various 

 fungi." In 1878, however, Prof. Burrill, of Illinois, discovered the true cause and 

 announced his discovery to the world. This was found to be a bacterial disease, due 

 to the presence of myriads of little germs in the inner bark and cambium. The germ 

 was called by Prof. Burrill Micrococcus amylovoriis from the eagerness with which 

 studies of Arthur at the Geneva Statoin in New York, and of Waite in the United 

 States Department of Agriculture, we know how this germ or bacterium lives, re- 

 produces itself and is carried from tree to tree. 



APPEARANCE OF BLIGHT. 



Luckily the disease is a very conspicuous one, which renders its presence 

 in an orchard the more inexcusable when well known. It affects twigs, leaves, 

 young fruit, and even the branches or trunks. From the experiments of Waite, 

 it has been found that it cannot attack the plant through the uninjured bark or 

 leaf. It can, however, gain entrance througla any injured place on trunk, limb 

 or even leaf. Its most common points of entrance are natural ones. These are 

 the young growing tips of the branch, the stigma of the flower, or the glands 

 which secrete nectar. Therefore the "flower-blight," the "twig-blight," and the 

 "branch or trunk-blight" are all forms of this disease. 



In the first, the young twig, especially if it be growing rapidly, turns black 

 in both leaf and stem, and whenever tlie leaves are blighted, they remain 

 black and dead through the ensuing winter. This black, piratical flag is the surest 

 evidence of its presence. 



In the "flower-blight" a whole bunch of flow^ers, or frequently every bunch 

 upon the tree will be affected, and dying back to the beginning of the spur, hold 

 the blackened flowers and young fruit also through the entire year. This is the 

 most common form on the apple. 



Frequently an entire limb or even the trunk will be affected for only a 

 short distance, while the top w^lll still be entirely free from the disease, and 

 this can only be understood when we speak of how the disease is spread. 



More frequently upon the pear several limbs and even the whole trunk will 

 be affected, and when this is the case the tree should be cut out root and branch. 



MEANS OF DISSEMINATION. 



If the young shoots of a tree affected with blight be examined, small drops 

 of sticliy. thick fluid will be found exuding from the edge of the diseased area. 

 If one of these drops be examined with a higli power of a microscope, myriads 

 of little oblong bodies will be seen, some separate, some in short chains. These 

 are bacteria. Arthur proved that these bodies, innoculated into a sound tree by 

 a needle, would produce the disease ; Waits proved to us beyond dispute that in- 

 sects, especially bees are the main instruments in their dissemination They are 

 Jittacted by the viscid sap. such up part or all of the drop, and then carry thou- 

 sands of tliese germs with them to innoculate flowers, shoots, or wounded 

 places in the bark. Undoubtedly heavy currents of wind assist in spreading the 

 disease and probably account for the commonness of "twig-blight." The question 

 comes right here : Sliall I keep bees if I have an orchard ? Certainly, and for 

 two reasons. First, the honey, and the revenue derived from it, are often no 

 small object to the farmer. Second, the bees are absolutely needed to assist in 

 proper cross-fertilization or pollination of the flowers. This leads us to the sub- 

 ject of remedies, for preventives there are none. 



