Vegetable and Field Crops 151 



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. 



While the salable part of the plant is not attacked, the 

 green part is largely decreased, so that the amount of nutri- 

 ment that can l)e stored away in the underground parts is 

 lessened. This results in diminished vigor and productive- 

 ness 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 as to necessitate the abandon- 

 ment of the beds. 



Rust is most injurious in light, dry soil; irrigation is, there- 

 fore, beneficial. Dew has been found to favor rust; there- 

 fore 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 the prevention of rust. 



The Palmetto varieties are quite resistant and offer a 

 solution of the rust problem in some localities. Careful 

 breeding has given rise to several strains known as " Washing- 

 ton asparagus" that are highly resistant. In dry climates 

 dusting with sulfur 150 to 200 pounds per acre, about three 

 weeks after cutting is finished and l^efore the rust appears, 

 is beneficial. It is best to sulfur early, and only when dew is 

 present. 



In regions subject to rain, where the sulfur treatment is 

 not applicable, three sprayings with sulfur-soda soap are 

 recommended: first in July, other applications at intervals of 

 three weeks. In New York three sprayings with Bordeaux 

 mixture with rosin added as an adhesive gave a gain of 

 S132.75 per acre. 



Minor diseases 



Anthracnose (CoUetotrichum sp.) is known by its numerous 

 black acervuli borne in a blanched background upon the 



