170 CHAPTER IX 



Tempanyii^ has brought forward evidence to show that the condition is 

 due to the combined action of chalk in the soil with sodium chloride carried 

 to the surface from deep-level waters. This observation explains the 

 dependence of the condition on season and the lack of correlation between 

 quantity of limestone present and severity of attack. 



The Control of Fungus Diseases. — The various methods by means of 

 which fungous diseases may be controlled are discussed below. 



I. By the Selection of Immune Varieties. — Of all the means available 

 this is the most elegant, and, since the recognition of the fertility of the cane 

 seed, a great part of the time of experiment stations has been devoted to 

 this end. Organized cane breeding had its inception in Java, where the 

 appearance of the sereh disease provided the stimulus. The pioneer in this 

 work was Kobus, and he succeeded in obtaining a number of varieties 

 which showed a high degree of resistance. In the British West Indies 

 and in British Guiana also, Harrison and other workers have obtained canes 

 that served to replace the older standard variety (Bourbon or Otaheite), 

 which before 1890 had become subject to the rind disease. In cases of other 

 epidemics, varieties already existing have served as substitutes for the 

 infected variety. A complete survey of immunity as it affects the cane 

 remains to be made, but certain isolated observations may be put on record. 



The Otaheite cane (q.v.), one of the most desirable of all varieties, is 

 also one which is very susceptible to disease, and has been the subject of 

 several epidemics. From the time of its introduction into Mauritius by Bou- 

 gainville till 1840 it fonned the principal cane grown. It then became subject 

 to an epidemic which at this space of time it is impossible to identify. ReHef 

 in this case was obtained by growing the Black Java cane, known in Mauritius 

 as Belouguet. What is probably the same cane as the Otaheite was again 

 extensively grown in Mauritius twenty years later as Louzier, and about 

 i8go this cane suffered from some disease. In this case relief was obtained 

 by planting the White Tanna variety. In the British West Indies the 

 Otaheite cane was grown almost exclusively from 1800 onwards, and about 

 1880 the first symptoms of the epidemic that became known as the rind disease 

 (q.v.) were noticed. Resource was had to the White Transparent cane, and 

 to seedhngs as they were developed, and, though still grown, the Otaheite 

 or Bourbon cane has never recovered its former position. Again in Pernam- 

 buco this cane suffered very severely in the 'sixties and the 'nineties from the 

 gumming disease, which also attacked it in Cayenne in 1859. This variety 

 has also been grown and attacked by disease in Madeira, Natal, and the 

 island of Hawaii. More recently it has begun to fail in the other islands 

 of the Hawaiian archipelago, where as Lahaina it had such a wonderful 

 record. This failure seems, however, due to soil conditions rather than to a 

 definite disease. 



Erwin Smith^^ failed to infect the variety D 74 with inoculations of 

 Pseudomonas vascularum to which gumming in other varieties is due. 



The variety B 20S has been observed in the West Indies to be very 

 susceptible to root disease. 



Butler has observed that the reed-like canes of India are more susceptible 

 to " smut " and more resistant to " red rot " than are the Paunda canes. 



The cane H 333 possessed of otherwise very desirable qualities was 

 found in Hawaii to be so susceptible to the leaf-disease " eye spot," caused by 

 Cercospora sacchari, that the stem was affected, and the whole cane killed. 



