DISEASES OF MINOR FRUIT PLANTS 347 



difficulties in dealing with soil parasites. Attempts at control 

 involve the very early eradication of affected plants and their 

 immediate neighbours, some effort towards sterilization of the 

 infested soil, the avoidance for a long time (at least a year and 

 possibly several) of the use of infected land for replanting, and 

 careful precautions against infecting new land with any sort of 

 material from the old. 



Resistant Varieties 



The most hopeful measure lies in the search for and adoption 

 of suitable resistant varieties. In Montserrat the Red Spanish 

 variety was reported first to be immune, and later to show a high 

 degree of resistance to the disease as compared with the Queen 

 types, which include the Ripley. 



Base Rot. 



A disease which has been previously described from the 

 Hawaiian Islands and is apparently indicated in a Porto Rico 

 reference, was observed in 1914 in a series of plots at the Experi- 

 ment Station in St. Kitts. 



Symptoms. 



The plots in question were estabHshed with cuttings of the 

 Ripley pine, which were disinfected with Bordeaux mixture 

 before planting. About the time the first fruits were beginning 

 to ripen a sickly yellow appearance of the plants became very 

 noticeable and was made the subject of investigation. It was 

 found that the more seriously affected plants were easily lifted 

 by hand and the number of living roots was very small. The 

 underground parts of the stem were rotted to a degree broadly 

 corresponding to the condition of the top, the worst cases re- 

 taining only a few roots attached immediately below the bases 

 of the lowest leaves. No evidence of attack on the remaining 

 roots and rootlets was found, the loss of roots appearing to 

 proceed from the rotting of the stem to which they were attached. 



The blackened tissues of the stem proved to be filled with 

 dark hyphae, penetrating the tissues in every direction, lying in 

 coils in the cells, and producing an abundance of black spores in 

 simple chains. A large plant with healthy green leaves and a 

 well-developed root system was found when cleaned to have a 

 brown spot about the middle of one side of the underground 

 stem, and when kept for four days in a closed chamber a rot of 

 the nature observed in the field had extended from this point 

 throughout the stem accompanied by the advance of the same 

 fungus. 



The fungus was identified in the plant and in cultures as 

 Thielaviopsis paradoxa, v. Hohn., the cause of pineapple disease 



