DISEASES OF PLANTS 93 



the shoot apices and the youngest leaves become browned and 

 finally die back. 



Anderssen makes no reference to the surface eruptions on the 

 shoot which are so characteristic of copper-deficient Citrus trees 

 as to give the name exanthema to the disease, and which are 

 recorded both by Thomas and his collaborators and by Pittman 

 as occurring in deciduous fruit trees. 



Analyses of leaves of affected and normal plum trees showed 

 that of the mineral constituents determined (CI, N, S0 4 , P0 4 , 

 Ca, Mg, K, Fe, Mn, Cu) the only ones which were present in 

 lower amount in chlorotic than in normal plants were manganese 

 and copper. Some of Anderssen's determinations are shown in 

 Table VI. No effect was, however, produced by applying 

 manganese to the chlorotic trees, but dipping chlorotic leaves 

 in a solution of copper sulphate (0-3 p. p.m.) cured the chlorosis, 

 and treatment of the soil with copper sulphate to the extent of 

 0-25-2 lb. of copper sulphate per tree brought about recovery 

 from the diseased condition. Isaac (1934) also reported the cure 

 of chlorosis in young peach trees in South Africa by the applica- 

 tion of copper sulphate to the soil, while manganese sulphate 

 effected no improvement. 



Table VI. Ash, manganese and copper content of leaves from 

 chlorotic and normal Kelsey plum trees. (Data from 

 Anderssen) 



Die-back of apple trees ('wither tip' or 'summer die-back') as 

 a result of copper deficiency has also been reported as occurring 

 in Western Australia by Dunne (1938), but the earlier sympt^ „ 

 of the disease do not seem to be quite the same as those described 

 by Anderssen. Thus Dunne makes no reference to rosetting, but 

 states that first brown spots and then small necrotic areas appear 

 on the terminal leaves. Eventually the leaves wither and fall, 

 and then follows the dying back of the shoot. Application of 



