XIII, A. 6 Reinking: Philippine Economic-Plant Diseases 253 



Causal organism. — The spores are brownish and usually- 

 spherical and are covered with blunt spines. They germinate 

 readily in water, producing- a promycelium with sporidia. 



Control. — Collect and burn all diseased parts. Crop rotation 

 should be practiced. 



Clasterosvorium maydicum Sacc. is found on leaves and is 

 often associated with Helminthosporium inconspicuum C. et E. 

 Leptosphaeria ortho gramma (B. et Br.) Sacc, Broomella zeae 

 Rehm., Physalospora linearis Sacc, and Acerhia maydis Rehm. 

 are found on corn trash during decomposition. 



CONTROL OF PLANT DISEASES 



GENERAL DISCUSSION 



The control of plant diseases involves primarily a prevention 

 of infection by the fungus. Before the method of prevention 

 can be fully understood, the true nature and cause of a disease 

 must be clear. The Filipino farmer must realize that plant 

 diseases are caused by specific organisms and that these 

 diseases can be communicated from one plant to another. The 

 •discussion of these various diseases has been taken up to point 

 out their nature, to show how to recognize them, to indicate 

 the damage they do, and to give the means of controlling them. 



PLANT SANITATION 



Many of the diseases discussed need no specific control meas- 

 ures. One of the most important general control measures is 

 that of plant sanitation. This term includes the destruction of 

 the diseased parts, together with the organism, and other allied 

 practices. It must be remembered that the organism producing 

 disease is present on the infected portions and that most of these 

 organisms are capable of living in the soil for some time. Con- 

 sequently in cases where it is practicable, all badly diseased plants 

 should be destroyed by burning. This will reduce the number 

 of spores and spore-bearing bodies that would have accumulated 

 in the soil. If the fungus be allowed to accumulate in the soil 

 from year to year and especially if the same crop be grown con- 

 tinuously on one piece of land, serious epidemics of disease are 

 apt to take place. 



CROP ROTATION 



The majority of fungi can develop only upon specific hosts and 

 live in the soil only for a short period of years. This brings up 

 the second and possibly most important sanitation measure, that 

 of crop rotation. Since a crop may be attacked by a definite 



