t.'fcJW YORK 





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JOINAL OF AGRICETDRAI ISEARCH 



Vol. XIX Washington, D. C, May i, 1920 No. 3 



PHILIPPINE DOWNY MILDEW OF MAIZE 



By William H. Weston, Jr.^ 



Pathologist in Charge of Downy Mildew Investigations, Office of Cereal Investigations, 



Bureau of Plant Industry, U^iited States Department of Agriculture 



During the past 20 years there have been reported from the Orient 

 several downy mildew diseases of maize, sugar cane, and other economic 

 grasses, caused by members of the genus Sclerospora of the Peronospo- 

 raceae. The most recently noted of these has been found in the Philip- 

 pine Islands, where it causes very serious damage to maize, a crop which 

 in area under cultivation is second only to rice. In 1916, a brief note 

 by Prof. Baker (7)^, of the College of Agriculture, first mentioned the 

 occurrence and destructive power of the disease. In 191 8, a short de- 

 scription of it with drawings of the causal fungus was published by 

 Reinking {17). No further information concerning this dangerous dis- 

 ease has been published, but it is known that it occasions heavy and 

 constant losses in the maize crop of this the richest of our oriental pos- 

 sessions and represents a grave potential menace to this extremely 

 valuable crop of our own country. 



The danger of the introduction of this disease to the cornfields of 

 America was felt to be sufficiently grave to warrant a full investigation 

 in the Philippines and elsewhere in the Orient. By such research it 

 was expected to determine the distribution and life history of this organ- 

 ism and to devise methods of control. With these data in hand, the 

 chances of promptly checking the disease were greatly increased should 

 it gain a foothold in the United States at any time in the future. In 

 the meantime, a quarantine was established against the importation of 

 corn from the Orient. 



It was the privilege of the writer to be detailed to this investigation, 

 and since April, 191 8, he has been at work on it in the Philippines. 



The following paper deals with the generalfeaturesofthedisease and with 

 the characteristics of the causal Sclerospora and its systematic position 



* The writer wishes to express his thanks to Dean Baker, Prof. Reinking, Prof. Elayda, and others at 

 the College of Agriculture of the University of the Philippines for so generously furnishing laboratory 

 facilities, land, and other assistance; to Mr. S. Apostol, of the Philippine Bureau of Agriculture, for infor- 

 mation on the distribution of the disease; and to Dr. E. D. Merrill, of the Bureau of Science, for many 

 courtesies which have aided the progress of this investigation. 



' Reference is made by number (italic) to " Literature cited," p. 121-122. 



Journal of Agricultural Research, Vol. XIX, No. 3 



Washington, D. C. May i, 1930 



t2 Key No. G-189 



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