PEAR DISEASES 



1639 



The Result of Growing a Tree with the Cen- 

 tral Leader. Blight infection made it neces- 

 sary to remove practically the entire bear- 

 in-g area of the tree. The limbs left are too 

 long and weak, (Original.) 



would be better to shorten to six inches 

 than to lengthen to 18 inches. Now that 

 pear blight has come this method of 

 pruning or forming the tree by main- 

 taining a central leader will have to be 

 altered. I know of perhaps five or six 

 hundred trees that have been wholly lost 

 on account of this style of growth; that 

 is to say, practically the entire bearing 

 portion of the trees had to be taken out 

 on account of blight girdling the leader. 

 In many young orchards which have 

 been planted within the past two or three 

 years, the growers are changing them 

 into the vase or open-head form, recog- 

 nizing the great difficulty in saving the 

 other type of tree should blight become 

 serious. In the larger trees it is a rather 

 difficult thing to change them over into 

 the vase form, but in every case where 

 blight has seriously damaged such trees 

 the resultant tree, of necessity, becomes 

 vase-formed when the blight is cut out. 



Severe pruning, though in most cases, 

 of course, giving good results in stimu- 

 lating vigorous twig growth and fruit 



production, tends also to result in more 

 serious attacks of the blight. Everyone 

 knows that the more vigorous the winter 

 pruning the more luxuriant the twig 

 growth during the following season. The 

 result always is that every dormant bud 

 tends to push, and, being very tender 

 and sappy, easily becomes infected and 

 blights badly. On the other hand, as 

 soon as the trees come into bearing, sum- 

 mer pruning, if practiced in the proper 

 way, will result in a more normal vege- 

 tative condition, and the tendency to set 

 fruit will also be correspondingly great- 

 er. A heavy set of fruit, other factors 

 being equal, will always tend to keep 

 down excessive vigor; and this is usually 

 a good thing under Pacific coast condi- 

 tions, where the growing season is quite 

 long as compared with conditions in the 

 eastern sections of the United States. 



Ciiltiyatioii, Fertilization and Irrigation 



Cultivation, fertilization and irrigation 

 are three very important factors to be 

 considered in connection with the control 

 of pear blight. I shall take these up sep- 

 arately, with only as much detail as will 

 make the text plain. Thorough cultiva- 

 tion is more essential, especially from 

 Southern Oregon southward on the Pa- 

 cific coast, than in the East, for the rea- 

 son that rainfall is not only much les'=«. 

 but from the spring of the year until 

 autumn the season is practically without 

 precipitation. In districts where irriga- 

 tion is practiced, cultivation is just as 

 necessary. In the East it is not an un- 

 common practice to permit pear and 

 apple orchards to grow in sod when it 

 is evident that the blight is getting be- 

 yond control. Everyone knows that lack 

 of cultivation induces surface evapora- 

 tion from the soil, and trees are thus 

 made to grow more slowly because of 

 lack of moisture, and hence, even very 

 susceptible varieties of pears and apples 

 do not blight badly, because the vegeta- 

 tive vigor is lacking. The necessity for 

 cultivation, as well as the method to be 

 used, varies so greatly in the Pacific 

 coast orchards that it is impossible to 

 make any general rule. Each soil type 

 requires different treatment, to the end 



