8 



CIRCULAR NO. 



126, BUREAU OF PLANT INDUSTRY, 



stance exudes from the bundles in the form of tiny drops. (See 

 fig. 3.) This is the most characteristic symptom of the disease. 

 Ordinary inspection, however, is not sufficient to detect this disease 

 in cases where the cane is only slightly attacked. 



Control. — Selection of cuttings and growing of resistant varieties 

 are recommended. 



SMUT. 



Smut ( Ustilago sacchari Rabenhorst) is rather widely distributed in 

 cane-growing countries, but usually does little damage. Mr. Butler 

 describes the disease as follows : 



Affected plants are known by the production from the growing apex of a long whip • 

 like dusty black shoot, often several feet in length and much curved on itself. (See 

 fig. 4.) 



This shoot is an entirely abnormal growth, devoid of leaves, slender, and flexible. 

 It must probably be taken to represent an abnormal floral shoot. In its earlier stages 



it is covered by a silvery white thin sheath which soon, 

 however, ruptures, exposing a dense black dust consist- 

 ing of the spores of the fungus. 



From the upper portion of the affected cane no sec- 

 ondary shoots arise, but from its lower part they are 

 fairly abundant, being all in their turn attacked and 

 prolonged into spore-containing organs. In this way it 

 becomes evident that the whole plant is affected. 



The tissues of the cane below the abnormal shoot con- 

 tain the filaments of the smut fungus. These are found 

 between the cells, not in them, as is the case with Col- 

 letotrichum falcatum. Diseased canes are poor in sugar 

 and worthless.' 



The disease may be transmitted through 

 spores coming in contact with healthy plants 

 or through diseased sets. The latter means 

 is probably the most frequent. 



Control. — Care should be exercised to pre- 

 vent the spread of spores through tools, cloth- 

 ing, packing, manure, etc., and only cane 

 from healthy plants should be used for the 



sets. 



SEREH. 



Fig. 3.— Gumming disease of su- The causc of serch is unkuown, although it 

 gar cane, showing gummy exu- ^ ^^^^^^ recoguizcd as far back as 1882 in 



dations on cut surface of cane. ^ 



(After Cobb.) Java, whcrc it has done much damage.- Dr. 



Lyon reports it to be of rare occurrence in the Hawaiian Islands, 

 having been first recorded in 1908. 



1 Butler, E. J. Op. cit. 



2 Di'crr, Noel. Cane Sugar. .Xllrinchain (M;uichesti'r), p. 14") 147, fii;- T2. 191 1. 



ICir. 12(;j 



