122 EXPERIMENTAL FARMS 



7-8 EDWARD VII., A. 1908 



affected that tliey are mucli disfigured by the disease and it will take some time before 

 they have regained a symmetrical shape. The Pear Blight is a bacterial disease and 

 is one of the most diificult to control. The only sure way of controlling it is to 

 remove every diseased tree or branch from the orchard, and if the trunk is affected 

 to remove all diseased parts. It will be readily seen that unless the work is done in 

 a very thorough and systematic manner it is practically impossible to cope with the 

 disease. As a general rule trees which are growing rapidly are worse affected, 

 the sappy wood being very susceptible to the disease; • hence any system of 

 culture that will cause a healthy but not strong growth is to be preferred. 

 It is rather difficult to grow good pears in sod in the pear districts, otherwise 

 the orchards might be let grow in grass, which would check the growth and 

 render the tree more immune. A better plan might be to loosen the ground in the 

 spring by harrowing or cultivating and then seed it down to some cover crop, as by* 

 this plan sufficient growth might be made to ensure good sized fruit and the growth 

 of the tree would be checked by the exhaustion of moisture by the growing covei* 

 crop. This disease has been known to injure fruit trees for more than one hundred 

 years and it is likely to continue to do so, hence some method of growing the trees 

 should be adopted which will as far as possible lessen the injury in addition to the 

 method just pointed out. By training pear trees so that the top will be made up of 

 several large branches in what is known as the vase form the chances of serious in- 

 jury is lessened as one branch may be affected and not the others and if the diseased 

 branch is removed the tree may be saved. If, however, the tree is of pyramirlnl 

 shape and infection takes place in the leader the disease may run dovm the main 

 trunk and the tree be destroyed. In addition to having a tree with a vase shaped or 

 branching top it is important to keep suckers or water sprouts removed as these may 

 carry infection to the main trunlj and the tree be destroyed. Fruit spurs should not 

 he left near the junction of the branches with the main trunk as if these are affected' 

 the disease may get to the main trunk. 



Some varieties of pears are less subject to blight than others, among these arc 

 Anjou, Kieffer, Seckel, Duchess, Winter Nelis, and Tyson, while the Bartlett and 

 Clapp are two of those which are most subject to it. It may then be desirable to plant 

 the varieties which are least subject to this disease. Another plan would be to top 

 graft the more susceptible varieties on the more resistant kinds as the chances of ihe 

 whole tree being destroyed would be considerably lessened. The Fire Blight which 

 affects apple trees, is the same as this disease. 



Spraying with Bordeaux mixture has no apparent effect upon it, but it is believed 

 that the lime and sulphur wash forming a coating over the bark prevents to some ex- 

 tent the entrance of the blight germ. 



The bacillus or germ of the Pear or Fire Blight finds its way into the tree at the 

 tenderest and least protected points and it is believed by those who have made a care- 

 ful study of it that practically all the infection is done by insects or birds and thaf 

 the disease is not carried to any extent by wind. Insects carrying infection travel 

 to the tips of succulent shoots and the germs find entrance through the buds at the 

 axils of leaves, and at any point where the bark is broken. The chief sources of in- 

 fection of bearing trees are through the flowers to which come insects bearing the 

 genns. 



The blight is usually first noticed in the spring on bearing trees when flowers and 

 flower clusters which have been blighted wither and do not set fruit. Soon the fruit 

 spurs are noticeably affected and also the new wood. The disease starting at the tip 

 of the shoots usually runs dovsm, although it will run in every direction, sometimes 

 passing on to the main branches and to the trunk of the tree. The disease varies in 

 the way it spreads. Sometimes only the flowers are affected or the fruit spurs or 

 smaller twigs, or patches about a place on the branches or trunk that have some 

 physiological injury. The germs are found in a gummy substance or exudation and 

 this is carried by the insects from one flower or tree to another. These bacteria in- 



