11 



should not be too moist at night, as this condition may cause 

 mildew (Cladosporium). In greenhouse culture the careful use 

 of water and the proper control of the moisture and light condi- 

 tions, should reduce the blossom end rot to a minimum. For 

 field culture supplying the crops with sufficient water would prove 

 beneficial. The irrigation of field crops will become more gen- 

 eral in the future, and will undoubtedly exert an influence not 

 only on the yield of the crop, but on the susceptibility to certain 

 troubles. 



RELATION OF EXTERNAL CONDITIONS TO 

 BLOSSOM END ROT 



The application of water to soil by sub-irrigation, even in 

 large amounts, is not always successful in preventing the blossom 

 end rot, as there are other factors which play an important part, 

 as already pointed out. While experimenting we had occasion 

 to observe the influence of the various external conditions on 

 the rot and gained some idea of their importance. One of the 

 most important factors which influences plant development is 

 sunshine, and when tomato plants are exposed to bright sunshine 

 conditions may arise which render the plants more susceptible 

 to the rot, as is shown in the following table. 



TABLE II. 



Tarle Showing Effects of Bright Sunshine on Blossom 

 End Rot of Tomatoes. 



Number of fruit, 

 Per cent of rot. 



The results shown in Table II give the differences in the 

 percentage of rot occurring on plants growing in the same house 

 in the same type of soil, but differently exposed. Those in the 

 front rows were exposed to strong sunlight, while those in the 

 back row were more or less shaded. The amount of rot on the 

 plants in bright sunshine was 36%, while in areas partially shaded 

 it was only 1.7 fo. The influence of sunlight on the rot is asso- 

 ciated purely with transpiration, since in the sunlight plants 

 transpire more than when partially shaded, and if transpiration 

 is active, more water is withdrawn from the plant, and some 

 portion of the plant may suffer. If water is withdrawn from 

 the fruit, cracking is more likely to occur, and the blossom end 

 rot will follow. 



Transpiration is more active, of course, in a house where the 



