DISEASES OF PLANTS 89 



Australia and New Zealand. According to Dennis (1937) the 

 disease was recorded in Australia as long ago as 1892, when it 

 was, however, confused with bitter-pit. The symptoms of the 

 disease are rather varied, and partly as a result of this a number 

 of names have been given to it including internal cork, drought 

 or drouth spot, corky pit, corky core, brown heart, poverty 

 pit, die -back and rosette. Internal cork refers to lesions which 

 first appear as clear or slightly greenish rounded regions, gener- 

 ally not exceeding 1 cm. in di° .ieter, and which may arise any- 

 where in the flesh of the f«.r t t. The patches become dry and 

 darken, and finally are dark brown in colour and of a corky or 

 spongy consistency according as the lesions appear earlier or later 

 in the developing fruit (Carne and Martin, 1937; Burrell, 1937). 

 In apples affected with drought or drouth spot the lesions are 

 in the form of large superficial patches, while in the case of 

 corky core it is the middle region including the core which is 

 affected. According to Burrell a greater deficiency of boron is 

 required to produce rosetting and die-back than to induce 

 internal cork in the fruit. Many investigators have demon- 

 strated that this disease can be controlled b}^ the application of 

 borax or boric acid to the soil (see, e.g., Askew, Chittenden and 

 Thomson, 1936). Internal cork does not appear so far to have 

 been recorded in Britain. 



There is evidence that boron deficiency may also induce the 

 formation of internal cork in the fruit and die -back of the shoots 

 in pears. 



Brown -spotting of Apricots. On certain light-textured 

 soils in New Zealand apricots tend to develop brown spots in 

 the flesh, especially near the stem end, and a dry, spongy con- 

 dition round the stone. This condition is attributed by Askew 

 and Williams (1939) to boron deficiency. The condition is con- 

 trolled by the application of \ lb. of hydra ted borax per tree to 

 the soil, or as a 0-1 per cent spray. The increase in the boron 

 content of the leaves and fruit resulting from these treatments 

 was accompanied by freedom from brown-spotting. 



