BULLETIN 231] WALNUT CULTURE IN CALIFORNIA. 367 



eially adapted to walnut culture, and where the maintenance of the 

 present groves is of as much or perhaps more importance than the possi- 

 bilities of planting new ones. The chief problem in walnut blight 

 control by spraying lies, in our opinion, not so much in the discovery of 

 a specific for the disease, since there is no reason why any good fungicide 

 should not be as good as any other for this purpose, but rather in the 

 development of means of spraying these large trees rapidly and econom- 

 ically and at the same time thoroughly. Investigations are still being 

 continued along this line, particularly in cooperation with Mr. C. W. 

 Beers, horticultural commissioner of Santa Barbara County, and a 

 renewal of spray work along new lines and upon a considerable scale is 

 being prepared for. 



Blight Control by Means of Applications to the Soil. Various sug- 

 gestions and experiments have been made along the line of applying 

 various substances to the soil with the idea of controlling walnut blight 

 by this means. Especially prominent has been the application of lime, 

 mostly beet factory refuse. It is impossible to state definitely just 

 what may have been accomplished by such methods as these, but it is 

 very certain that nothing of this sort has resulted in blight control to an 

 extent at all significant or important. In trees which are suffering for 

 plant food the growth may be stimulated and increased by heavy appli- 

 cations of stable manure or nitrogenous fertilizers, and as a result of 

 this the crop may be increased and the loss by blight lessened. This we 

 believe to be the extent of any good results which may be obtained by 

 the application of any substance to the soil. 



Resistant Varieties. It has been noted ever since walnut blight first 

 became prevalent in California that there is a great difference in indi- 

 vidual trees as to the extent to which they are affected by the disease. 

 Some trees regularly lose almost all their nuts by blight, others are no- 

 ticeably free from it, while others vary from year to year, being badly 

 blighted one year and comparatively free from the disease the next. As 

 a result of such observations the possibility of selecting or producing 

 blight immune varieties was suggested several years ago. Pierce in his 

 work considered this phase of the matter, and brought together a collec- 

 tion of walnut species and varieties from various parts of the world, as 

 well as local selections, with this object. On account, however, of the 

 discontinuance of his walnut work no definite results along this line have 

 ever been announced by Professor Pierce. Various nurserymen have 

 also worked to some extent along the same line, endeavoring to pick 

 out and propagate from individual trees of uniformly large production 

 of nuts. The fact was early established that the extent to which indi- 

 vidual trees blight depends with much regularity upon the season at 

 which the trees develop in the spring, trees late in coming out being 



