BtTLER AND HAPIZ. 175 



to six years, probably with bad results.' At Samalkota a two years' 

 "dry" rotation (not followed by paddy) and a three years' "wet " 

 rotation (followed by paddy) were tried, but found unsatisfactory. 

 On the other hand, at Pusa, cane one year in five has been satisfactory 

 and the non-irrigated cane in Bihar usually gets a much shorter 

 rotation. The fungus appears to die out rapidly in moist soil, but 

 cultures exposed to the air and kept moderately dry retain their 

 vitality for at least five months. In Hawaii, Lewton-Brain found 

 that plate cultures allowed to dry out invariably gave no sign of 

 vitality after three months. But if cane is present, there seems to be 

 little doubt that Colletotrichum fives and spreads through the soil 

 and, in the young irrigated crop, passes from trench to trench, either 

 with the seepage of irrigation water, on the feet and implements of 

 coolies or (though less certainly) by direct growth through the soil. 

 It has been shown that the roots are readily infected and we have 

 lost several series of comparative experiments at Pusa through 

 ground infection of control trenches. Fortunately the radius of 

 spread does not appear to be large and if the measures detailed 

 above are carried out, little injury should be caused in this manner. 



In spite of all these precautions, serious attacks of red rot, 

 from circumstances not ordinarily under control, may occur from 

 time to time. We have met with two such cases. One was the out- 

 break at Pusa in 1907-08, which was, without doubt, the result of an 

 epidemic of cane-fly {Pyrilla aberrans) on the cane that year. 

 Leaf-hoppers are w^ell known in other countries to be associated with 

 bad attacks of fungus diseases as, for instance, in Hawaii, where 

 ■■ rind disease "" follows with great intensity the epidemics of leaf- 

 hoppers. It is probable that the action of these insects is chiefly 

 to reduce the vitality of the cane and render it increasingly sus- 



1 Wood, R. C. Scientific Report for the Samaikota Agricultural Station for 1908-09. 

 Government Press, Madras, 1909. 



■2 The cause cf this disease is not yet quite clear. Howard in the West Indies and 

 Went in Java held that it was identical with red rot, the fungus, Mdnnconium Sncchari, 

 prev^iously believed to be its cause, being merely a follower of Colletotrichum fnkalum. 

 Subsequent workers, such as Lewton-Brain, Cobb and Edgerton in the West Indies, Hawaii 

 and Louisiana, have reverted to the previous view, though quite recently South and Dunlop 

 have failed to establish the parasitism of Melanconium Sacchari. In the East, this fungus has 

 not been recorded as a parasite. 



