DISEASES OF CULTIVATED PLANTS 647 



mental importance to the future of chestnut nut culture. Al- 

 though the nuts are distinctly inferior in flavor to the European vari- 

 eties, such as Paragon, the Japanese chestnut is already grown on a 

 large scale as a nut-producing tree. There are, however, many trade 

 varieties of dubious origin. Some of these may prove later to be sub- 

 ject to the disease. Immunity tests of all known varieties of chest- 

 nuts have been undertaken. 



Attempts will also be made to hybridize the Japanese with 

 American and European varieties, with the hope of combining the 

 immunity of the former with the desirable qualities of the latter. 



However excellent as a nut and ornamental tree, the value of 

 the Japanese chestnut as a forest tree is doubtful. It can be recom- 

 mended only experimentally at present for forest planting. It cer- 

 tainly will not take the place of the American chestnut. The tree is 

 said to attain a height of 50 or 60 feet in Japan. As seen in this 

 country it is a handsome tree, dwarfish and compact in habit, and 

 rather slow growing. It has hardly had time to show how large it 

 can grow. (B. P. I. B. 121, Part VI.) 



The immunity of the Japanese chestnut, together with the fact 

 that it was first introduced and cultivated on Long Island and in the 

 very locality from which the disease appears to have spread, suggests 

 the interesting hypothesis that the disease was introduced from 

 Japan. So far, however, no facts have been adduced to substantiate 

 this view. 



WALNUT. 



Blight. Causes a black spotting on the surface of the young 

 nuts, many of which drop prematurely. Affected nuts which reach 

 full size have the contents blackened and spoiled. The shoots are 

 also affected with the production of black, canker-like areas, most of 

 which heal out as the wood hardens, leaving wounds and cankers of 

 considerable size. Many of the small fruit spurs and twigs are en- 

 tirely killed, but the disease does not kill large limbs or whole trees. 

 The leaves are also affected in black spots. The disease varies in 

 abundance from year to year, being most prevalent in seasons with 

 much fog and moisture late in the spring. 



No practical remedy has been found for this disease, but the 

 problem has been largely solved by the development of immune 

 varieties. Such trees are now available to a limited extent and must 

 soon supplant the present plantings of seedlings or susceptible kinds. 



Some control may possibly be obtained by spraying with Bor- 

 deaux mixture or sulphur sprays just before the buds open. The 

 expense of spraying walnut trees thoroughly is so great, and so much 

 time is required to thoroughly cover trees of this size, that we have 

 no faith in a satisfactory solution of the walnut blight problem along 

 this line. (Cal. E. S. B. 218.) 



On old groves liberal fertilization with nitrogenous fertilizers, 

 together with the use of green manure crops, will go far towards 

 making up for the losses caused by the disease. Most walnut proves 

 would be benefited by more irrigation than they receive at present, 



