CULTURAL DIRECTIONS 225 



times. It is controlled in practically the same manner 

 as the common asparagus beetle. The Asparagus miner 

 (Agromyza simplex) sometimes causes damage. The 

 adult is a small black fly, but the stalks are injured by 

 the maggot, which mines under the skin in the lower 

 part of the stalk. The eggs may be destroyed on lure or 

 trap plants, which are burned in late June or early July. 



287. Rust is practically the only disease that has 

 caused any damage to asparagus. It made its appear- 

 ance in this country in 1896, and has since caused heavy 

 losses in almost all important asparagus-growing dis- 

 tricts. Hexamer ("Asparagus," p. 138) describes this 

 fungous disease as follows: "When an asparagus field is 

 badly infested with the rust the general appearance is 

 that of an unusually early maturing of the plants. In- 

 stead of the healthy green color there is a brown hue, as 

 if insects had sapped the plants or frost destroyed their 

 vitality. Rusted plants, when viewed closely, are found 

 to have the skin of the plants lifted, as if blistered, and 

 within the ruptures of the epidermis the color is brown. 

 The brown color is due to multitudes of spores borne 

 upon the tips of fine threads of the fungus, which aggre- 

 gate at certain points and cause the spots. The threads 

 from which the spores are produced are exceedingly small 

 and grow through the substance of the asparagus stem, 

 taking up nourishment and causing an enfeebled condi- 

 tion of the victim, which results in loss of the green 

 color and the final rustiness of the plant, due to the mul- 

 titude of spores formed upon the surface. These spores 

 are carried by the wind to other plants, where new dis- 

 eased spots are produced; but as the autumn advances 

 a final form of spore appears in the ruptures that is quite 

 different in shape and color from the first ones produced 

 through the summer. The spores of late autumn, from their 

 dark color, give an almost black appearance to the spots." 



Mowing and burning the tops every fall, after they 



