DISEASES OF CULTIVATED PLANTS 531 



DISEASES OF VEGETABLES. 



ASPARAGUS DISEASES. 



Asparagus Rust (Puccinia Asparagi). This is caused by a 

 fungus of the above name which is one of the true rusts or Ure- 

 dineae. Like many other rusts, it appears in three different stages 

 or forms of development. The first of these forms, called the aecidial 

 or cluster cup shape, appears in early spring, but, since at that 

 time the .asparagus is being cut for market, the fungus is able to de- 

 velop only upon such scattering stalks as are allowed to remain and 

 grow up, and consequently is not at all noticeable at this season. In 

 this stage the fungus produces little eruptions on the surface of the 

 affected plants, each of which is a minute cavity in which numerous 

 spores are developed in the form of long chains, which break up into 

 separate roundish spores at maturity. These spores are carried by 

 the wind to other plants and produce on them the second form of 

 the rust. 



Summer or Red Rust Stage. The rust is by far the most de- 

 structive in the red rust stage which appears in July and August. 

 The plants in the main bed have been allowed to grow up by this 

 time and if badly affected soon appear as if scorched by fire, having 

 a dry and withered appearance and being of a reddish brown color. 

 The fungus consists as usual of numerous fine filaments which grow 

 through the tissue of the plant just beneath the surface, robbing it 

 of its nourishment and thus interfering with its vital processes. 

 Upon the surface appear numerous little blisters which soon burst 

 open and discharge a reddish brown powdery substance, consisting 

 of the red or uredospores of the fungus. These spores fly off as a 

 cloud of fine dust when badly rusted plants are disturbed. They are 

 carried in enormous quantities to all neighboring plants where they 

 germinate and spread the disease. 



The Fall or Black Rust Stage. The third form of the rust ap- 

 pears in September and October on plants which have survived thus 

 far. It is characterized by the appearance of small black excres- 

 censes upon the surface of the affected plants, which are clusters of 

 the spores of this stage. These spores are very thick walled and thus 

 suited to their function of surviving over winter. They remain dor- 

 mant until spring when they proceed to germinate and reproduce 

 the disease, now in the spring stage. 



The best means of controlling the rust is by thorough cultiva- 

 tion in order to secure vigorous plants, and in seasons of extreme 

 dryness plants growing on very dry soil with little water-retaining 

 properties should if possible receive irrigation. (Mass. E. S. B. 01.) 



BEAN DISEASES. 



Bean Anthracnose. The anthracnose is at present the most 

 common and destructive disease of be'ans. It is very probably the 

 disease that is destroying your crop. Its most apparent injury is on 

 the pods, where it forms large dark rusty brown or black spots. It is 

 on this account frequently known as pod spot. The disease may and 

 usually does occur, however, on all parts of the plant except the 

 roots. It is caused by a fungus known to botanists as Colletotri- 



