248 



The Philippine Journal of Science 



Fig. 37. 



is attacked by a fungus. The root system is healthy. Isola- 

 tions from a large number of stems gave a Fiisarium that 

 produced a pinkish growth in pure culture. 

 LEAP spot: cercospora 



Symptoms. — Leaves may be 

 spotted with definite circular 

 spots from 1 to 3 millimeters 

 in diameter. Spots have gray 

 centers with purplish borders. 



Causal organism,. — Typical 

 Cercospora conidia and coni- 

 diophores are developed (fig. 

 37). The conidia are tapering 

 and usually have from four to six 

 cells. Germination takes place 

 in water overnight. Conidio- 

 phores are produced in groups 

 and are light brown and septate. 

 They also may germinate and 

 produce infection. 



Control. — Crop rotation will 

 keep the disease at a minimum. 



POD spot: phoma bakeriana saccardo 

 Symptoms. — This fungus is found growing on mature pods, 

 where it produces minute black specks. 



powdery mildew: erysiphaceae 



Symptoms. — A white powdery 

 mildew may cover all parts of 

 the plant. This disease is not 

 serious and appears during cool 

 dry weather. It has been ob- 

 served in abundance on Vigna 

 catjang Walp. 



Causal organism. — Conidia and 

 conidiophores are produced in 

 abundance, but as yet no perithe- 

 cia have been observed (fig. 38) . 



Control. — The disease is not 



serious enough to warrant any fig. 38. a species of Erysiphaceae. on 



special control. Crop rotation ^'""^ catjang w^p. Myce- 



"^ ^ hum and conidiophores with 



should be practiced. chains of conidia (X 825). 



Cercospora on Vigna sinensis 

 End), o, group of conidio- 

 phores with immature conidia 

 attached (X 350) : b. conidia 

 (X 350) ; c, germinating coni- 

 dia (X 350) ; d, germinating 

 conidiophores ( X 350 ) . 



