120 Journal of Agricultural Research voi.xix. N0.3 



In any case, however, the increasing attention which these dangerous 

 downy mildews of maize have demanded by their destructive activity 

 throughout the Orient in recent years must necessarily arouse the appre- 

 hension of all who are concerned with the valuable com and sugar-cane 

 interests of the United States. 



SUMMARY 



(i) For several years there has been known to occur in the Philippine 

 Islands a destructive downy mildew of maize, which not only causes 

 serious losses in that region but also threatens our own valuable corn 

 crop, should it reach the United States. Prior to investigations by the 

 writer no extensive study of this disease has been made. This paper 

 presents certain results in regard to the distribution, severity, and char- 

 acteristics of the disease and the nature and relationships of the causal 

 fungus. 



(2) The disease occurs throughout the Philippine Islands, where it 

 evidently has been established for some years. 



(3) It is extremely destructive. Under favorable conditions whole 

 fields are destroyed, and in some districts it has even forced the natives 

 to abandon com culture entirely. 



(4) Representative varieties of all types of maize are highly suscepti- 

 ble, and teosinte, maize-teosinte hybrids, and sorghum are attacked, 

 but with less virulence. Inoculation experiments on a number of re- 

 lated plants, both wild and cultivated, gave negative results. 



(5) Symptoms of the disease may appear from the time the plants are 

 seedlings with three or four leaves to the time the tassels and silk are 

 developed. In general, infected plants show a yellowing of the leaves 

 in more or less restricted striped areas, a whitish down of conidiophores, 

 principally on the leaves, abnormalities in growth of the vegetative parts, 

 and abortive development of the ear, resulting in partial or complete 

 sterility. These effects of the disease are described and illustrated. 



(6) The causal fungus belongs to the genus Sclerospora of the Perono- 

 sporaceae and is characterized by the predominance of its conidial 

 stage, the lack of oospores, so far as known, and the invariable germina- 

 tion of its conidia by hyphae. In these respects it differs from the type 

 species Sclerospora graminicola (Sacc.) Schroet., which is distinguished by 

 its evanescent conidial stage, its predominating oospores, and the ger- 

 mination of its "conidia" by zoospores. The Philippine species shows 

 close relationship to the following recently described oriental species, 

 all of which attack maize : Sclerospora javanica Palm, of Java, Sclerospora 

 maydis (Rac.) But., of British India, and Sclerospora sacchari T. Miy., of 

 Formosa, Queensland, and the Fiji Islands. 



The Philippine Sclerospora appears to be a new species and is described 

 as Sclerospora philippinensis , n. sp. 



