37 



As a result of considerable experience in summer pruning of the 

 pear blight, we are able to say that the common fault is that the limbs 

 are usuall}^ cut off too near the part which is diseased. It is best to 

 make the cut at least a foot below the lowest blackening visible. In 

 certain cases the disease may even have spread farther down than this 

 without showing on the surface. 



Fall or winter pruning. — This is, after all, the most important method 

 of combating the disease. Examination of pear trees in the early 

 winter will disclose the fact that most of the blighted limbs still have 

 the dead leaves clinging to them, while the health}^ limbs are bare. 

 Careful search will also reveal the fact that in most of the limbs the 

 disease has run its course and a sharp boundary line exists between 

 the dead dr}^ bark and the living green bark*. It is of no importance 

 whatever whether these dead blighted limbs be removed or not. In 

 them the blight germ has perished and from them there can be no 

 further spreading of the disease. In a ver}^ few cases, however, 

 especially in young water shoots, it will be found that the bark is black 

 and juic}', not dry, and that the disease- darkened bark fades gradually 

 into the healthy bark. In these the blight germ is living, and it is in 

 such branches that it survives the winter. If every branch containing 

 living germs could be cut off in winter well below the lowest trace of 

 the disease, pear blight could be exterminated. But a single limb of 

 this kind may infect a whole orchard the following season. It is 

 preferable to burn such branches; but if the pruning is done before 

 February it is not necessary. It is very important, however, to take 

 care that new inoculations of the disease are not made with the prun- 

 ing knife or pruning shears. Merely cutting into diseased branches 

 and then health}^ ones frequently starts new infections; therefore, 

 extreme care must be taken to keep the tool used free from the living 

 germs. 



To avoid the danger of losing the whole tree or larger branches the 

 trunk should be kept free of water shoots and the fruiting spurs should 

 be removed from the lower parts of the larger branches as suggested 

 by Waite. If this is not done the blight may run down the short fruit 

 spur and thus destroy a large branch. It is safe to say that 90 per 

 cent of the infections which take place in the flowerless sprouts are 

 probably caused by the punctures of insects which have just visited 

 diseased parts. Experiments indicate that in no case can the blight 

 enter an uninjured leaf or twig. 



Virulence of the disease in the Northwest. — The above recommenda- 

 tions are based on the records of Eastern experience with the disease. 

 It must be confessed the three years' experience with the disease in 

 the inland fruit-growing districts of the Northwest have been dis- 

 couraging. Intelligent use of the knife both in summer and fall will 

 enable one to save his trees, more or less mutilated, however. 



