xui,A, 5 Reinking: Philippine Economic-Plant Diseases 233 



diameter, but may be irregular with corners, 16 microns wide 

 by 50 microns long. 



Control. — In severe cases of infection spraying may be highly 

 desirable. Plants should be sprayed with Bordeaux mixture at 

 the slightest indication of the disease. Spraying should be car- 

 ried on at intervals of a week. Crop rotation also should be 

 practiced. Badly diseased plants should be collected and burned. 



RAPHANUS SATIVUS LINN. RADISH 

 BACTERIAL SOFT ROT : BACILLUS CAROTOVORUS JONES 



Symptoms. — A bacterial rot of the root frequently occurs. 

 The rot starts while the radishes are still in the ground, and 

 in advanced cases the entire roots disintegrate into a soft mass. 



Causal organism. — The rot is due to bacteria, being similar 

 to the root rots produced by Bacillus carotovorus Jones. Cul- 

 ture characters have not been worked out, so no definite identity 

 of the organism can be given. 



Control. — Diseased carrots should not be allowed to disin- 

 tegrate in the field, but should be collected and burned. If the 

 field be infected with the bacteria, crop rotation will have to 

 be practiced. When carrots are stored, care should be taken 

 to avoid injuries. The surface of the root should be allowed 

 to dry in the sun, and storage should be in a well-ventilated 

 place. 



SACCHARUM OFFICINARUM LINN. SUGAR CANE 



BLIGHT: RHIZOCTONIA 



Symptoms. — During excessively damp weather and in thick 

 plantings sugar cane may be attacked by a Rhizoctonia, which 

 kills the young leaves and eventually the entire plant. The in- 

 fected portions assume at first a watery appearance, then turn 

 brown, and fall over. Brown sclerotial bodies are produced 

 over the old infected parts (Plate XVI, fig. 1). 



Causal organism. — The fungus spreads over the tender leaves 

 and penetrates and causes the death of the cells. No spores 

 have been observed; however, sclerotial bodies are formed in 

 abundance. Good growth is produced on potato agar. In young 

 cultures a rather coarse mycelium is produced, and in older 

 cultures the sclerotial bodies are formed. They are white 

 masses at first, but turn brown and hard when older. 



Control. — Infected plants should be destroyed. Plantings 

 should not be too thick. 



