72 Diseases of Truck Crops 



ing here, or wobbling there, to the great danger of its 

 stability. For we must recognize at the outset that 

 disease is but variation in directions dangerous to the 

 life of the plants. That the passage from health to 

 disease is gradual and ill-defined in many cases 

 will be readily seen." Excluding the injury from 

 insect pests, the diseases of truck crops may be con- 

 sidered as follows: 



A. DISEASES OF A MECHANICAL NATURE 



Diseases brought about by mechanical injuries are 

 very numerous and varied. Truck crops such as 

 spinach, lettuce, etc., are cultivated for their edible 

 tender parts. It is not strange that such crops should 

 be susceptible to injuries of a mechanical nature. 



WIND STORMS 



Wind storms are often the cause of great losses to 

 the trucker. This is especially the case in soil dis- 

 tricts of a sandy nature. Strong winds cause the 

 sand to be thrown about in the field with consider- 

 able force and velocity. The small sand particles 

 blown violently on plants cut the foliage and not 

 infrequently the fruit too. Tomatoes, watermelons, 

 eggplants, in fact, all the tender crops, suffer greatly 

 from sand or dust storms. Besides this form of 

 injury, dust or sand storms carry off large quantities 

 of fertilizer. Moreover, sick particles of soils may 

 be carried by the wind from farm to farm, and in this 



