DISEASES OF CULTIVATED PLANTS 527 



irregular corky projections coalesce to form a large raised corky 

 scab. In less severe attacks, especially when scab occurs on grape- 

 fruit and on tangerines (or rarely on sweet oranges), the warty irreg- 

 ular projections are wanting, and there will be seen more or less 

 raised platform-like patches variable in shape and extent. The sur- 

 face of the raised portion is finely scabbed or lightly scurfed, as is 

 seen in the case of thrips marks or silver scurf. In this milder form 

 it can usually be distinguished from thrips marks or other forms of 

 scurf, by its being raised, but can be distinguished with certainty only 

 by the use of the compound microscope. 



The scab can be completely controlled by the use of weak Bor- 

 deaux mixture (3-3-50). Since the use or Bordeaux on orange 

 trees, however, kills the friendly fungi and allows a rapid increase of 

 scale insects or whitefly, this spray is not recommended except when 

 it is absolutely necessary. When it must be resorted to, a good insec- 

 ticide should be used as soon as the scale insects begin to increase 

 rapidly. Some of the harm from increase of scale insects may be 

 prevented by spraying the Bordeaux as much as possible only on the 

 fruit, and keeping the spray off of the larger limbs and the inside of 

 the tree where the friendly fungi may be left alive. (Fla. E. S. 

 B. 108.) 



Splits. Splits are fruits in which the skin and rind have broken 

 in a line, exposing the interior of the fruit. They are caused by a 

 development of growth pressure within the fruit accompanied by a 

 lack of expansion of the skin and rind. This lack of expansion is 

 due either to disease markings as in the case of fruit marked by die- 

 back, or to a too early maturity of the skin and rind on account of 

 unfavorable growth conditions. The splitting occurs when some 

 point of weakness develops in the skin and rind that releases the 

 pressure. The conditions that bring on the growth pressure within 

 the fruit are unknown. 



A case of splitting occurred on fruit growing in the greenhouse. 

 The point of weakness in the rind was made by a chemical injury. 

 The tree on which the fruit grew had been watered daily with a 

 given amount during the period of development of the fruit. It is 

 observed that if heavy rains follow a period of drought in the fall, 

 the number of splits will be greatly increased. During the drought 

 the fruit is soft to the feel, indicating a lack of turgidity in the cells. 

 Following the rains, the fruit becomes quite solid, indicating a rapid 

 increase of liquid in the fruit. 



Splitting is commonly associated with disease or drought in the 

 grove. The prevention of disease conditions will Drevent the splits 

 that develop with these conditions. Drought conditions in the grove 

 can be avoided by the use of irrigation and of cultivation to conserve 

 the moisture. 



Creasing. This is a form of splitting in which the peel breaks 

 only partially, the skin remaining whole and covering the break. 

 It is easily recognized by the feel, and can be followed with the eye 

 by the depression of the skin along the line of break. The condi- 

 tions causing creasing are probably closely related to those causing 



