312 Diseases of Truck Crops 



Hollow Heakt 



Cause Uneven Growth. 



When potatoes are overgrown or when quick growth 

 results from dry spells followed by moist weather, 

 the heart of the tuber tears and a hoUow center is 

 formed (fig. 58 f). The trouble does not injure the 

 edible quality of the tuber. Varieties such as Rural 

 New Yorker and King are especially susceptible to 

 hoUow heart. So far as possible these should be 

 avoided on heavy soils. 



Tip Burn 



Caused by Unfavorable Soil and Weather. 



This trouble is prevalent in dry weather in mid- 

 summer, when the leaves transpire water more 

 rapidly than the roots can take it in from the soil. 

 As a result the tips and margins of the leaves dry 

 up and die (fig. 58 h). The uprolling of the margins 

 of the leaflets is a characteristic of tip bum, also 

 distinguishing it from late blight. The trouble may 

 be considerably reduced by frequent shallow culti- 

 vation, making a shallow surface mulch which will 

 prevent excessive evaporation. Spraying will also 

 protect the foliage from tip bum. 



Mosaic 



Cause Unknown. 



Mosaic is a disease which is not confined to the 

 tubers, but which also affects the parts of the plant 



