DISEASES OF CULTIVATED PLANTS 605 



symptoms the tap root of a wilted plant is shorter, and the lateral 

 roots less abundant. 



This disease is due to a microscopic plant, a fungus which goes 

 by the name of Neocosmospora Vasinfecta. It is found in an 

 actively growing state in the soil existing on decaying organic mat- 

 ter. The soil then is its original home or habitat and in this place 

 its existence is that of a saprophyte. But when it enters the root 

 and stem of a cotton plant it changes its nature and becomes 

 parasitic. 



Cotton wilt cannot be controlled by spraying with fungicides 

 for the cause of the trouble is found within the plant. The soil, 

 which is the natural habitat of the fungus, has been treated in vari- 

 ous ways with poisonous substances. None of these solutions have 

 as yet proven efficient. On the other hand they have not only 

 proved impracticable but expensive. 



It has been suggested that the soil can be freed from this disease 

 through a system of rotation, yet data have been collected to show 

 that this takes from seven to ten years and the results are not as 

 promising as one would expect. Deprived of cotton as a source of 

 food the fungus still continues living by subsisting on decaying 

 matter and so prolonging its life as a saprophyte for a term of years. 

 Wilt gradually diminishes when the land is put into rotation but is 

 not entirely eradicated for the period of time mentioned above. The 

 destruction in the fall of all diseased plants lessens in a measure the 

 spread of this disease. At the same time it kills the boll weevil and 

 other injurious insects, and keeps the land in better sanitary 

 condition. 



The most efficient method of control lies in the use of resistant 

 varieties that can develop well and reach maturity in spite of the 

 adverse soil conditions wilt infected soil. These wilt resistant 

 forms have been produced by breeding and selection. Mr. Orton 

 of the Department of Agriculture has produced resistant varieties 

 from both the upland cotton and the Sea Island cotton. Those of 

 the Upland variety are the Dillon and the Dixie. Those of the Sea 

 Island are the Rivers and the Centerville. The farmers that have 

 wilt sick land should by all means plant seed raised from wilt 

 resistant varieties. 



Anthracnose. The condition of the weather has much to do 

 with the amount of anthracnose. A very dry season hinders the 

 development of the spores and affords a natural means of checking 

 the spread of this disease. On the other hand a wet season creates 

 the most suitable conditions for its development and spread. So 

 little is known about this disease that we are not yet in position to 

 give a complete discussion. 



Anthracnose, pink boll, or boll rot is determined primarily 

 from external characteristics. It is most destructive as a boll 

 disease, yet it also injures the stem, leaf and cotyledons of young 

 seedlings. The first indication of trouble on the boll i.-< shown in 

 the appearance of small reddish brown spots, which grow larger 

 and become depressed in the tissues of the boll. Soon the spores 



