330 DISEASES OF CROP-PLANTS 



SCLEROSPORA DISEASE. 



This disease was described for the first time by Miyake, in 

 Formosa, where it appeared in 1909. It is believed, however, to be 

 the same as the leaf-splitting disease known earlier in Australia 

 and Fiji. It was introduced into the Philippines, apparently in 

 cane cuttings from Formosa. The earliest symptoms on the leaf 

 show as a few yellowish stripes parallel with the veins ; the stripes 

 increase in number until the greater part of the leaf turns pale 

 and becomes marked by scattered long reddish-brown spots. 

 At the same time a fluffy growth appears on the under surface 

 and the leaf dies and dries up or before dying becomes torn or 

 shredded at the tip. In some varieties of cane the internodes may 

 be much lengthened or thickened and diseased stalks may be 

 2-3 feet longer than uninfested stalks. The cause of the disease 

 is a downy mildew — Sclerospora Sacchan Miyake, which sporulates 

 abundantly on the under sides of the leaves during the night. 

 The disease is transmitted by infected cuttings and from plant 

 to plant under humid conditions by means of the air-borne 

 conidia. Maize and teosinte {Eiichlcena Mexicana) become 

 infected readily but endure the disease better than cane. At- 

 tempts have been made to control the disease by roguing the 

 young plants which have arisen from infested cuttings before the 

 spores of the fungus are developed on the leaves, and by careful 

 seed-piece selection from uninfected stools. If Sclerospora 

 disease reached the West Indies it would find difficulty in main- 

 taining itself in the islands having a dry climate. 



