XIII, A, 5 Reinking: Philippine Economic-Plant Diseases 235 



and may cover a large portion of the leaf. On the under sur- 

 face of these spots is developed the light gray to brownish 

 dust, which contains the same 

 spores as found on the younger 

 spots (Plate XVI, fig. 2). 



Causal organism. — The coni- 

 dia are produced in abundance 

 on the lower surface of the 

 leaves. Conidia are typically 

 elongated with tapering ends, 

 hyaline, and four- to five-celled 

 (fig. 29). The conidiophores 

 are produced in groups from the 

 stomata. They are rather ir- 

 regular, brownish, and septate. 



Control. — The disease is not 

 serious enough to warrant a 

 specific control. General sanita- 

 tion and the growi;h of resistant 

 varieties are usually sufficient, 

 attacked less than the Hawaiian cane. In severe cases of infec- 

 tion all infected leaves should be burned after harvest. 



Cercosuora. On Saccharum offi- 

 cinarum Linn, a, group of 

 conidiophores (X 320) ; b, coni- 

 dia (X 320) ; c, conidia (X 

 640). 



The native cane is generally 



LEAF spot: PHYLLACHORA SACCHABI P. HENNINGS 



Symptoms. — This is a rather uncommon and nondestructive 

 leaf spotting. The disease is characterized by the production 

 of a black stromatic mass extending through the leaf. Stromata 

 are sparingly scattered on the leaf surface. Phyllachora sac- 

 chari spontanei Syd. is found in greater abundance on the wild 

 sugar cane, Saccharum spontaneum Linn. 



Other leaf spottings are present, do little or no damage, and 

 as yet have not been identified. 



RIND disease: melanconium sacchari massee 



Symptoms. — This stem disease is common in many fields. 

 It does most damage among plants that lack vigor, due to poor 

 cultural methods. In well-kept fields the disease is only slightly 

 in evidence, and little damage is done. Entire fields of weakened 

 cane may be killed by the fungus. Diseased canes at first are 

 prematurely yellowed and later the leaves dry, followed by 

 the death of the plant. In the later stages tips of infected 

 shoots shrivel. Finally the entire cane shrivels and turns brown 

 to black. During the early stages no fruiting bodies have been 



