DISEASES OF CULTIVATED PLANTS 649 



only remedy for this trouble is to thin out the trees where they are 

 too closely planted and give the soil better care. Most of these old 

 hard shell orchards, even at best, have now become so unprofitable 

 and undesirable as to make it seem better for the owners to cut down 

 the trees and use the land for some other purpose. 



The second form of die-back mentioned, that occurring in young 

 trees which have formerly been thrifty, killing them down to the 

 forks or even to the ground, is a very serious matter at present in 

 some districts. The trouble shows usually to & greater extent in a 

 certain portion of the orchard or in certain orchards worse than in 

 others near by. It developed more extensively in the spring of 1911 

 than ever before, when a great many trees which had seemed healthy 

 and vigorous the previous fall were found to be almost entirely dead 

 in the spring. Affected trees failed to leaf out at the proper time and 

 more or less of the top proved to be either entirely dead or developd 

 very slowly later in the season. Such trees often threw out new 

 growth or suckers toward the base, which made a very vigorous 

 growth, while the tops were dead or very slow in coming out. The 

 leaves which finally developed from the affected limbs had a yellow, 

 sickly appearance. 



This trouble is more or less the same as that described under 

 walnut Yellows, and evidently has been caused by the abnormally 

 dry season of 1910. The disease is practically the same in its nature 

 as that described as the Little Leaf of the peach and shows similar 

 relations. Trees standing over coarse, dry subsoil or those which 

 had for any reason become drier than usual during the fall of 1910 

 showed the trouble the worst. Young trees under ten years of age 

 showed the trouble worse than older ones. It is a common practice 

 in some of the worst affected districts to grow alfalfa between the 

 walnut rows and in groves or portions of groves which for this reason 

 became drier than the average late in 1910 the trouble has been 

 walnut rows and in groves or portions of groves which for this reason 

 on account of several years' irrigation and handling of alfalfa pre- 

 vented the moisture reaching the subsoil and thus the same effect 

 was produced. Frost was also responsible to a greater or less extent 

 for the dying back of trees in dry ground. 



Trees affected in this way should be pruned back to good live 

 wood, if not too far gone, and it is not to be expected that a new top 

 will soon be produced. By popular attention, to irrigation late in the 

 season, especially in dry years, it is not to be expected that the trouble 

 will occur again save in soils most unsuitable for walnuts on account 

 of coarse subsoil near the surface. We may say here that in choosing 

 crops for interplanting walnuts, it is not desirable to let the ground 

 remain in alfalfa too long unless an abundant water supply is -avail- 

 able, and one can be sure by actual examination that the soil is suffi- 

 ciently moist at all times, both for the alfalfa and for the trees. In 

 any event, it is ordinarily best to leave a cultivated strip at least 

 eight feet wide on each side of the tree row, and as the trees grow 

 older it is better to plow out the alfalfa and grow some annual crop 

 which will receive regular cultivation, as well as irrigation. 



