196 DISEASES OF ECONOMIC PLANTS 



hibernating condition in which the causal fungus must rest 

 until the following spring before it can induce further in- 

 fection. 



During the first two stages spores in enormous quanti- 

 ties are liberated by the least movement of the plants 

 by animals or wind, and the spores, carried to their 

 new prey, produce infection if conditions of moisture are 

 present. 



The effect upon the plant is serious. While the salable 

 part of the plant is not attacked, the green part is largely 

 decreased and its starch-forming power diminished, so that 

 the amount of nutriment that can be stored away in the 

 underground parts is lessened. This must result in dimin- 

 ished vigor and productiveness of such roots the following 

 season. 



The loss may range from 15 to 35 per cent of the crop 

 the year after the first attack, while in three years the 

 more susceptible varieties may be so nearly destroyed that 

 the beds must be abandoned. In some states the invasion 

 of this disease has almost, if not quite, prohibited com- 

 mercial asparagus growing. 



The rust is most injurious in light dry soil ; irrigation is, 

 therefore, beneficial. Dew has been found to favor the 

 rust; therefore shaded, dewy localities should be shunned, 

 as should also rows running at right angles to the prevailing 

 winds. Clean culture methods, cutting and burning all 

 tops in the fall, and destroying all wild asparagus aids in 

 preventing the propagation of the rust. 



The Palmetto varieties are quite resistant and offer a 

 solution of the rust problem in some localities. In dry 

 climates dusting with sulphur 150 to 200 pounds per 



