xni. A, 6 Reinhing: Philippine Economic-Plant Diseases 249 



rust: uredo vignae bresadola 



Symptoms. — This is a rust that may do severe damage to the 

 plants. Usually it is not common enough to be very destructive. 

 Characteristic, brown rust sori are produced on the under leaf 

 surface. 



XANTHOSOMA SAGITTIFOLIUM SCHOTT. YAUTIA 

 LEAF spot: VERMICXJI/ARIA xanthosomatis saccardo 



Symptoms. — A small leaf spot sparingly scattered over the 

 leaves. Little damage is done. 



Yautia was mentioned before as a plant to replace the conunon 

 Philippine gabi, the latter being badly infected with disease. 

 Yautia is entirely free from the attacks of Phytophthora. 



ZEA MAYS LINN. CORN, MAIZE 

 BLA.ST OF KERNE2,S: FUSARIUM 



Symptoms. — Individual mature kernels will frequently swell, 

 burst open, and expose the starch. The starchy blasted area 

 is usually covered with a pink growth of mycelium (Plate 

 XX, fig. 3). 



Causal organism. — A Fusarium is associated with the disease. 

 The mycelium penetrates the grains and produces spores on 

 the surface. 



Control. — The disease is usually not severe. Planting should 

 not be too thick, so as to allow for plenty of aeration. 



DOWNY mildew: SCLEROSPORA MAYDIS (RAC.) BUTLER 



Symptoms. — This is a serious corn disease found in India, 

 Java, the Philippines, and undoubtedly in other tropical 

 countries. In Java recent work has shown that the disease is 

 due to Sclerospora javanica Palm, which is not identical with 

 Sclerospora maydis (Rac.) Butl. In the Philippines we have the 

 same fungus described by Butler of India, Sclerospora maydis 

 (Rac.) Butl. There appear to be in the East two mildew dis- 

 eases, identical in appearance, but caused by two different fungi. 



Downy mildew of corn is a serious disease in the Philippines, 

 often killing entire portions of fields. It is most severe during 

 the rainy season. Young plants, from 10 to 60 centimeters 

 in height, first exhibit the disease. Upper younger leaves are 

 the first to become affected. Lower outer leaves are normal. 

 Diseased leaves are characterized by the production of white 

 stripes running parallel with the margin (Plate XX, fig. 2). 

 Frequently the entire young leaves are whitened. This diseased 



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