DISEASES OF CULTIVATED PLANTS 451 



may wilt and die when the real and actual trouble is in the roots, 



4. Look first for the simplest effects, such as those of animals, 

 frost or other climatic influences, simple injuries or other obvious 

 causes of trouble. 



5. Look for indications of alkali, salt, poor drainage, too light 

 or too heavy soil or other injurious soil conditions, as shown by sur- 

 face incrustations, the occurrence of native vegetation peculiar to cer- 

 tain conditions or any peculiarity in the appearance of the soil in, 

 the region of the affected plants. 



6. Look for the presence of fungi, insects or other parasites, so 

 far as one's ability extends in this direction. Endeavor to observe 

 accurately and judge intelligently whether the organisms found are 

 the cause of the trouble or simply secondary. 



7. If nothing is found above ground to indicate the cause of 

 the trouble, dig or bore a hole to the depth reached by the lowest 

 roots. During the digging notice the condition of the roots, the con- 

 sistency of the layers of soil, the amount of moisture which they 

 contain, and their relation to the development of the roots. Look 

 carefully for any peculiar or suspicious condition, either in the roots 

 or soil, and continue the examination out to the smallest roots and 

 down to an ample depth. 



8. Ascertain as closely as possible all that can be found out about 

 the previous history and treatment of the soil and plants, all infor- 

 mation of possible value as to irrigation practice, fertilization, cul- 

 tural methods and previous climatic conditions; also the nature of 

 the trouble from its very first appearance. 



9. If necessary, examine healthy groves, trees or plants of the 

 same kind, making the same examinations and inquiries, and en- 

 deavor to ascertain wherein conditions differ from those where the 

 trees or plants are diseased. 



After this examination, if more information is desired, endeavor 

 to select the most characteristic samples, either of parts of the plant 

 or soil, and send them to the proper authority with complete infor- 

 mation as to the nature and occurrence of the trouble. In sending 

 parts of plants, pack them so that they will remain as fresh as pos- 

 sible. In obtaining soil samples take a fair sample from each foot 

 down to a depth of four feet. (Cal. E. S. Bui. 218.) 



APPLE, PEAR AND QUINCE DISEASES. APPLE. 



Crown-gall, Hairy-Root or Tumors. On the apple tree this 

 disease appears most often on the trunk and larger limbs, but in a 

 number of instances it has been found affecting the twigs and smaller 

 limbs. The tumors on this tree are exceptionally large at the be- 

 ginning, and frequently appear in the form of a smooth swelling 

 surrounding the base of a dormant bud, quite often the terminal bud 

 of a twig, and may be noted at the end of the growing season. In 

 the form usually occurring on many other trees, the swellings appear 

 on twigs and limbs indiscriminately, apparently having no connec- 

 tion with the formation of buds. The tumors vary greatly in size 

 on the same and on different trees ; some are as small as a pea; others 

 attain a size of 2 to 3 inches in diameter. This variation in size is 



