2 Department Circular 329, U. S. Dept. of Agriculture 



It is evident that uncontrolled reduction in yield due to the 

 ravages of disease is one thing and a decrease in production due 

 to a purposeful and intelligent limitation of acreage, which when 

 planted is given proper protection, is quite another. In the first 

 case we have uncertainty and waste of labor, land, and expenses 

 incident to growing the crop; in the second case we have economy 

 and some certainty of obtaining normal production. 



Although the effect of some plant diseases is limited to reduc- 

 tion of yield in the field, other troubles not only cut production, 

 but may cause blemishing of the fruit, either making it unmarket- 

 able or throwing it into a low grade. Nail-head spot of tomatoes, 



Fin. 1. — Decreases in yield due to disease may be very serious. Ninety acres of 

 Martinis wheal which had to be plowed under, the field having been ruined by 

 scab. (Reproduced from Farmers' Bulletin 1224.) 



apple scab, and potato scab are examples (fig. 2). Still others, 

 as brown-rot of peaches, potato late-blight, and sweet-potato black- 

 rot, not only prevent the yield of part of the crop, but so affect the 

 harvested product as to cause decay in storage and transit (fig. 3). 

 To the wastage caused by this latter type must be added destruc- 

 tion by still another group of diseases, which, although of little or 

 no importance in the field, may be responsible for extensive losses 

 during the marketing period (fig. -1). For example, Rhizopus rot 

 of sweet potato, though not recognized as a field disease, may be 

 very destructive after harvest. Approximately 11,168,000 bushels 

 of sweet potatoes rotted in storage during 1922 as a result of the 

 action of plant diseases. In that same year the American railways 

 paid claims on losses of fruits and vegetables in transit amounting 

 to approximately $8,830,000. A great part of this sum. with its at- 

 tendant expenditures for payment of the army of clerks and others 

 necessary to handle the adjustments, represents losses in transit which 

 were largely brought about by plant diseases. 



