8o Diseases of Truck Crops 



interference with the normal transpiration, and the 

 reduction of leaf surface. 



It seems that not all truck crops are equally sub- 

 ject to smoke injury. Potatoes seem to be very sen- 

 sitive to its effect, while peas are the most resistant. 



Methods of Control. There is as yet no definite 

 method of control known. All that the trucker can 

 do is to avoid the smoke belts. The greatest in- 

 jury occurs in the line of the general direction of the 

 winds. These areas therefore should be avoided. 

 As far as possible, irrigation should be postponed 

 during windy days. The injury from the smoke is 

 greatest when the soil is wet. Truckers have a 

 right to expect reimbursement in case of loss from 

 smoke injury, when the offending factory is set up 

 subsequent to the trucker's settlement in that place. 



B. DISEASES DUE TO PHYSIOLOGICAL CAUSES 



In this class are included disturbances which are 

 due to unfavorable conditions of nutrition. There 

 are numerous diseases of plants which are brought 

 about by lack of, or by an excess of, certain food 

 elements in the soil. The effect is an interference 

 with the proper life functions of plants. 



MALNUTRITION 



Caused by improper food supply. 

 Symptoms. The symptoms of malnutrition are 

 not always the same. They differ somewhat with 



