WALNUT 



growth the first year, many of them not more than 6 

 inches. After this the growth is rapid. The trees are 

 tied to stakes with strips of cloth, since they are very 

 tender when growing, and the swaying of the tree by 

 the wind quickly causes any other tie to cut through 

 the bark. Walnut trees are pruned very little. At first 

 small limbs are allowed to start about 

 the trunk, but later these are pruned off 

 to a height of i feet. Some of the longer 

 growths are shortened back while the 

 trees are young; and after they are older 

 tin- low limbs which bend down in the way 

 of cultivating are removed. 



The Santa Barbara Softshell begins to 

 bear the third year from planting, but 

 does not produce profitable crops before 

 the fifth or sixth year. Precocity in bear- 

 ing is not a desirable quality in Walnuts, 

 since no Walnut tree will produce a prof- 

 itable crop until it attains sufficient size 

 to support it. Hardshell trees do not 

 bear as young, and they are not regular 

 bearers. 



Walnut orchards in California receive 

 thorough tillage. They are heavily irri- 

 gated in winter, and plowed about 8 in. 

 deep in the spring. After this they are 

 irrigated and cultivated until the nuts be- 

 gin to fall, — about the 1st of September. 

 Late irrigation fills out the nuts and 

 causes the hull to open readily. Heavy 

 fogs are also desirable during harvesting. 

 The nuts are shaken down and picked up. 

 They are then spread in trays about 5 

 in. deep until dry, when they are bleached 

 and shipped to market. Walnuts were 

 formerly bleached with fumes of sulfur, 

 but this was found injurious to the nut. 

 They are now usually (lipped in a solution 

 of chloride of lime (chlorinated lime) and 

 sal-soda, to which a sufficient amount of 

 sulfuric acid has been added to set free the chlorine. 



The majority of Walnut-growers are organized into 

 local associations. Representatives of these associa- 

 tions form the executive committee of the Southern 

 California Walnut-Growers' Association. This execu- 

 tive committee provides the form of contract which 

 the local associations may enter into with brokers, 

 and fixes the price. The local associations are man- 

 aged in several ways. In some the growers bleach 

 their own crop, while in 

 others the association performs 

 this work at its own packing 

 house. 



The Walnut tree has very few 

 pests. The red spider some- 

 times attacks the trees, but it is 

 SJ'-l^^.i^'.'^fyfl not considered a serious pest. 

 V*Slfr '.*^OT'K ° f late y ears a bacterial growth 

 ' has developed to a considerable 

 extent which is more serious. 

 This attacks and destroys the 

 immature nut and the small 

 limbs of the tree. 



Arthur Staley. 

 The Walnut in Central 

 California. Walnut -growing 

 is quite rapidly extending in 

 both the coast and interior val- 

 ley regions of Central California 

 and is also successfully accom- 

 plished in favorable situations 

 in the foothills up to an eleva- 

 tion of 2,000 ft. There are also 

 many instances of thrifty and 

 prolific trees in northern Cali- 

 fornia and southern Oregon. 

 This northward extension of 

 successful Walnut growing is 

 conditioned upon the use of the 

 best French varieties and the 

 rejection of the varieties popu- 

 lar to the chief commercial dis- 



WALNUT 



1961 



tricts in southern California, viz., Prffiparturiens, May- 

 ette, Chaberte, Parisienne, Frauquette, etc. These va- 

 rieties are hardier in resistance of frost and leaf-burn 

 from summer heat. They are largely root-grafted upon 

 the seedlings of the California Black Walnut in the nur- 

 sery and are also being top-grafted upon old native trees. 

 E. J. Wickson. 



J -VTj 



2711. Juelans cinerea of 

 the eastern states. 

 (X %.) 



The California Wild Wal 



Walnut Bacteriosis. — Chief among the more serious 

 diseases of Jitglans regia m the United States is a bac- 

 terial blight of the nut, branch and leaf of that tree. 

 This blight now has its greatest development along the 

 Pacific coast, especially in Orange and Los Angeles 

 counties, California. The germ which causes this dis- 

 ease is a newly described species of Pseudomonas (P. 

 juglandis). Different effects of the disease are shown 

 in Fig. 2714. 



The organism of Walnut bacteriosis winters in the 

 fallen nuts, in the diseased tissues of affected branches, 

 and especially in the pith cavity of the latter. New in- 

 fections occur as soon as spring growth begins, taking 

 place near the growing point of branches, in the open- 

 ing leaves, and upon the young and tender nuts. The 

 finer lateral veins of the leaves and the adjoining par- 

 enchyma are destroyed, and the midrib is often af- 

 fected. The injury resulting from infection of the branch 

 will largely depend on the tenderness of the latter at 

 the time and point of infection. If the tissue is tender 

 a canker-like spot will be eaten through to the pith, or 

 the entire end of the shoot may be destroyed. If the nut 

 is infected while small, its complete destruction usually 

 follows, the digestive action of the germ involving hull, 

 shell and kernel. Nuts infected early in the season 

 mostly fall when small, while later infections frequently 

 result only in the destruction of the hull and the black- 

 ening of the outer layers of the shell, the tissues hav- 

 ing become too hard for the further progress of the dis- 

 ease. As in the case of pear blight, rapidly growing 

 trees are more subject to injury than those making a 

 slower and hardier growth. The spread of the micro- 

 organism through infected branches is generally only 

 local — it rarely extends more than a few inches from 

 the point of infection. A marked blackening of the in- 

 jured parts results from the rapid oxidation of the tan- 

 nic acid they contain, though this is not distinctive 

 of injury from this disease. Pseudotnonas juglandis 

 is actively motile; hence fogs, rain or dew aid in its 

 spread and increase the number of infections. The 

 water of irrigation mny carry the germ for miles. 



The destruction of the tissues of the Walnut is effected 



