FORTY-FIRST ANNUAL REPORT. 87 



FIRE r.UGHT AND ITS CONTROL. 



A. W. EIDSON. 



This disease is caused by the bacteria bacillus ainylovorons. It was 

 first observed about 1780 by William Deuniug. It probably occurred as 

 a disease of the Avild fruits of North America before cultivated varieties 

 were introduced. For a long time it was confined to the regions east 

 of the Rocky Mountains, but in 1903 it ap])eared in California. 



Fire blight is the most destructive disease of the pear, and is also 

 a serious disease of the ajjple. Not only is the crop lost, but also parts 

 or even the whole tree is destroyed. When you stop to think what a 

 bearing tree is worth, you get some idea as to the loss from this disease. 



The pear blight is most commonly noticed during the early part of 

 the season, throughout the blossoming period of both the pears and 

 apples. From two Aveeks to one month from the period of pollination 

 the blossoms and tips begin to wilt and show signs of blackening and 

 the death of the si)urs and branches upon which fiower clusters were 

 born. Upon the pear the blight may continue down the spur or branch 

 entirely killing it as the disease progresses. If the spur which is affected 

 is on a large branch, or on the body of the tree, the disease will work 

 down the spur into the branch or body and cause a deadened portion, 

 but not killing the branch, this is .called a canker. This may, however, 

 extend entirely around the affected part thus girdling it. Many of 

 these cankers live over winter and in the spring a sweetish liquor oozes 

 forth which is filled with the bacteria. This liquid attracts bees and 

 they get completely covered with the bacteria ; then they light on the 

 blossoms and leave some of the bacteria. This accounts for the disease 

 starting from the blossoms. 



The disease being caused by bacteria, thus being entirely inside the 

 tree, makes it impossible to control it by means of a spray. The only 

 means of control are to avoid a succulent growth, this being favorable 

 for the growth of the disease. Destroy all sources of infection, clean 

 out all cankers, make a regular inspection of every tree in the orchard 

 at least once a week throughout the growing season; beginning as soon 

 as the ])etals begin to fall. It is sometimes necessary to inspect every 

 day, cutting out all affected twigs and rubbing off all affected spurs 

 and water sprouts as fast as they start. 



In cutting out ahvays cut about twelve inches below the affected 

 portion and disinfect well with a corrosive sublimate solution (1 to 

 1000). The corrosive sublimate is sold in tablet form, and to make 

 up this solution dissolve one tablet in one pint of water. 



All varieties of jsears are susce])tible to the disease, however the Bart- 

 lett, Seckel, and LeCont are much more susceptible, and the Kieffer is 

 the least susceptible. 



