be far better to rotate cane with some legiiminons crop, such as sword 

 beans, cow-peas, or velvet beans. 



5. Effort should be made to reduce to a minimum cane injured 

 through attacks by borer, other insects, cattle, rats, or other agencies ; 

 such injured canes being readily attacked by various fungi. Gaining 

 a foothold on injured canes, the fungi may spread to adjoining 

 healthy cane. 



6. Cane should not be allowed to become overmature, since many 

 diseases are capable of causing severe damage to such cane. This 

 applies i)articularly to Meancomum and CoUetotriclium which often 

 ruin whole fields of certain varieties. It must be noted that some 

 varieties can be left until a second season without cutting, provided 

 they are growing under good conditions, but they must be watched, 

 since the disease, once it gets a foothold spreads very rapidly. 



SUMMARY. 



Fungi liave caused heavy loss in the cane fields of Porto Rico. 

 Diseases have been present in serious amounts since at least 1870 

 and are quite prevalent at the present time, presenting a number of 

 difficult problems. Cane diseases have been studied in Porto Rico 

 by various agronomists and commissions of the Spanish times and 

 since the American occupation to some extent by the Federal Experi- 

 ment Station. Most of the work in this field has been carried out 

 by pathologists of what is now the Insular Experiment Station. 



There are a considerable number of important cane diseases not 

 occurring in Porto Rico, "sereh," gumming, etc. 



Of the fungi found chiefly on the roots or base of the stalk are 

 Marasmius sacchari, Himantia stcllifera, and Odontia sacchari. These 

 are all concerned to a greater or less extent in the so-called root 

 disease. Studies on their exact relationships and parasitism have 

 not yet been carried out. 



The principal diseases of tlie stalk are red rot (Colletoirichum 

 falcatum, rind disease, (Melanconium, sacchari), and a new disease 

 due to Cytospora sacchari, which proved threatening to certain varie- 

 ties. The two former diseases especially attack overmature or injured 

 cane. 



A ninnber of leaf diseases are found, none of which cause appre- 

 ciable loss although they are of universal occurrence. Those described 

 are red spot of the leaf -sheath (Cercospora vaginae), red rot of the 

 leaf-sheath (Sclerotium Rolfsii), eye spot {Helminthosporium sac- 

 chari), ring spot (Leptosphacria sacchari), brown leaf spot {Cercos- 

 pora longipes), red stripe, and wither-tip. 



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