230 



The Philippine Journal of Science 



Round, smooth brown sclerotial bodies may be produced on dead 

 plants. 



Caiisal organism. — The causal organism is a common soil fun- 

 gus attacking a large number of plants and has been discussed 

 under citrus and coffee. 



Control. — The disease is not generally severe. Crop rotation 

 should be practiced. In infected fields, planting should be timed 

 so as to avoid the excessive rainy season. 



LEAF spot: cercospora lussoniensis saccardo 



Symptoms. — This common spot is widely distributed on field, 

 garden, and Lima beans. Spots are irregularly roundish, usually 



3 millimeters to 1.5 centimeters 

 in diameter. The smaller spots 

 are reddish brown ; larger spots 

 have ashen gray centers bor- 

 dered with reddish brown rings. 

 Spots may run together, thereby 

 covering large portions of the 

 leaf surface. 



Causal organism. — Spores and 

 conidiophores are of the char- 

 acteristic Cercospora type. The 

 conidia are elongated and 

 hyaline; conidiophores are in 

 groups and brownish (fig. 26) . 

 Control. — The disease is mod- 

 erately destructive, but not enough so to warrant any definite 

 control except general sanitation and crop rotation. 



LEAF spot: PHYLLACHORA PHASEOLINA SYDOW 



Symptoms. — Phaseohis calcaratu^ Roxb. is frequently attacked 

 by this fungus. The disease is characterized by the production 

 of black spots scattered over the leaf surface. Spots are black, 

 bordered with a straw-colored ring, roundish, sometimes elong- 

 ated, raised, extending through the leaf to both surfaces, and 

 made up of hard, shiny, stromatic masses of fungus mycelium. 



Causal organism. — The stromata are roundish bodies extend- 

 ing through the leaf. Within the stromata are the perithecia, 

 in which are produced the asci and ascospores. Each stromatic 

 mass usually has one, or sometimes two, perithecia. 



Control. — The disease is not serious on cultivated varieties. 

 Crop rotation should be practiced to prevent epidemics. 



Fig. 26. Cercospora lusaoniensis Sacc. 

 from Phaaeolus lunatus Linn. 

 a, group of conidiophores (X 

 340) ; b, germinating conidia 

 (X 340). 



