360 PEAR GROWING IN CALIFORNIA. 



BRIDGE-GRAFTING AFTER REMOVAL OF LARGE AREAS OF BARK IN 



BLIGHT WORK, 



In cases where it has been neeessary to remove so much bark that the 

 tree is endangered because of the sap not heing able to flow in sufficient 

 quantities from the roots to the branches and vice versa, it becomes 

 necessary to bridge-graft. If a tree is completely girdled, then this is 

 the only means of saving it; if only partially girdled it may live and 

 thrive without such grafts. Not many of the California pear growers 

 who have found it necessary to carry on a campaign against blight in 

 their orchards have resorted to the use of these grafts, but have con- 

 sidered that a tree when girdled by blight was not worth trying to 

 save. There is no question that under certain conditions their use pays. 

 Figs. 155 and 156 illustrate this work as it has been done in one of the 

 leading pear orchards of the Sacramento Valley. Some of the scions 

 used in this orchard are six feet or more in length. The process of 

 grafting is simple, consisting merely in the insertion of one end of a 

 twig in the good bark below the injured portion and the other end in 

 the same manner above. As in all grafting operations it is only neces- 

 sary that the cambium layers of the trunk and scion come in contact at 

 some point where union will take place. The ends of scion can be cut 

 in any convenient way to bring this about. After insertion beneath the 

 bark the ends are carefully waxed over to exclude the air and to prevent 

 drying. Once union takes place they grow very readily. Water 

 sprouts growing from below a girdle or injury may be utilized by cut- 

 ting off and grafting in the upper end in the good bark above the 

 girdle. It may also be practical at times to plant young trees by the 

 side of old ones for the purpose of grafting them into the trunks of the 

 latter when they serve exactly the same purpose as the grafts in the 

 other cases mentioned. 



PREVENTIVE MEASURES. 



Since rapid, succulent conditions of growth are favorable to blight it 

 follows that anything which will prevent such growth will retard the 

 disease. For this reason it is not best to fertilize too heavily when trees 

 are growing under conditions that are very favorable and which are 

 inclined to bring about excessive growth. An abundance of water may 

 have a similar effect in lessening the trees' resistance to blight. There- 

 fore withholding irrigation water in times of serious blight epidemics 

 may render the trees less liable to contract the disease. 



The control of insect pests which serve as carriers, and which inocu- 

 late the trees wnth the blight organism is another important factor in 

 the control of the trouble. One of the most troublesome insect pests is 

 the ant. There are various species which may be found in orchards. 

 They are especially bad when the trees are infested with aphids or 

 scale insects, as the droppings of these insects, known as honeydew, 

 are a favorite food of the ants. These pests are so exceedingly active 

 that they crawl over all parts of a tree and wherever a case of holdover 

 exists, they are almost sure to carry it to the blossoms where infection 

 takes place. The disease may then be readily carried by bees and 

 other blossom visitants among the insects. This illustrates the great 



