74 TRACE ELEMENT DEFICIENCY 



contained no measurable amount of zinc, and in all cases rosette 

 was severe or common in the districts supplied. In the sixth 

 case the water contained a measurable amount of zinc (0-14 

 p. p.m.) and the district was essentially free from rosette. 



The evidence presented by Finch and Kinnison thus supports 

 the view that zinc is an essential element for the growth of the 

 pecan, and that when there is a deficiency of it the condition 

 known as rosette results. The favourable effect of zinc in con- 

 trolling pecan rosette was also recorded by Demaree, Fowler 

 and Crane (1933) working in Georgia. 



Another member of the Juglandaceae, the walnut, may also 

 exhibit the effects of zinc deficiency, but according to Chandler 

 (1937) these do not include rosetting, although the leaves are 

 mottled, crinkled and rather small. 



Little Leaf or Rosette of Deciduous Fruit Trees. Similar 

 to pecan rosette is the disease of deciduous fruit trees known in 

 California as little leaf. The most characteristic symptom is the 

 development in the spring of rosettes of very small leaves 

 which, according to Chandler, Hoagland and Hibbard (1932), 

 who have made a special study of the disease, generally possess 

 less than 5 per cent of the area of normal leaves. The affected 

 leaves generally exhibit a chlorotic mottling. Shoots bearing 

 normal leaves may develop later in the season below the little - 

 leaf rosettes, but as the season proceeds the new leaves are pro- 

 gressively smaller and mottled and may be abnormal in shape. 

 Sometimes after one or two years, in other trees after a much 

 longer period, the branches begin to die back. Fruit generally 

 fails to set on badly affected branches and any which does is 

 small and malformed. Stone fruits tend to have brown areas in 

 the flesh (Chandler, 1937). Chandler, Hoagland and Hibbard 

 mention apple, pear, plum, cherry, peach, apricot, almond and 

 grape as all liable to the affection. 



Concluding that little leaf was not the result of attack by 

 micro-organisms, Chandler, Hoagland and Hibbard sought for 

 its cause in the soil. As a result of various fertilizer trials they 

 found that affected trees responded to the application of ferrous 

 sulphate, but only when this contained zinc as an impurity. 

 Further trials showed that it was the zinc that was actually 

 responsible for the improvement. Solid injection of zinc sulphate 



