MANUAL OF GENERAL AGRICULTURE. 87 



are usually overlooked. Make drawing of a blighted blos- 

 som spur. 



7. Fruit Blight. Frequently only one blossom on a 

 spur is infected and by the time the bacteria have killed 

 it and worked their way down the pedicle to the spur 

 itself, the uninfected blossoms have developed fruit of a 

 considerable size. From the spur the bacteria now work 

 into the base of these fruit pedicles and by way of 

 them to the growing fruit. Study Fig. 6, Cornell Bui. 272. 

 The curculio and aphids frequently introduce the bacteria 

 into the fruit through their punctures. The disease does 

 not always enter the fruit by the pedicle. Note that the 

 leaves of the spur are also dead and shriveling. In rainy, 

 muggy weather the bacteria ooze from these blighted 

 fruits and blossoms in sticky drops as they do from the 

 hold-over cankers. 



8. Twig Blight. The bacteria from the diseased 

 blossoms and fruits are carried by sucking insects to the 

 tips of the growing shoots and waterspouts and are there 

 introduced through the wounds or punctures made by the 

 insects into the tender, succulent tissues. Here they mul- 

 tiply rapidly, killing the shoot, causing the form of the 

 disease commonly known as "Twig Blight." Blighted 

 twigs have been taken from the tree in summer and 

 pressed. Examine the specimen provided and observe : 



9. The contrast between the diseased and healthy 

 portions of the twig in both the twig and leaves. You may 

 be able to find the dried ooze. Draw the blighted twig. 



10. In some of the specimens note that the dormant 

 buds in the axils of the leaves just below the blighted por- 

 tion have been prematurely forced. Explain this. 



The organism that causes this disease is Bacillus amy- 

 lovorus. See Fig. 6, Cornell Bui. 272. 



11. Control of the Disease. No method of protecting 

 the trees by means of sprays is effective because it is im- 

 possible to reach the bacteria. The disease can be effect- 



