XIII, A, 4 Reinking: Philippine Economic-Plant Diseases 207 



lus calcaratus Roxb. all produced typical disease on Phaseoltts 

 lunatus Linn., Phaseolus vulgaris Linn., and Phaseolus calcara- 

 tus Roxb., which shows that the organism causes a general 

 blight of beans under suitable conditions. 



Further inoculation experiments show that under suitable con- 

 ditions this organism may attack and kill a large number of 

 succulent plants (Plate X, fig. 1). A pure culture isolated from 

 soy beans killed the following seedlings in an experiment carried 

 out in a damp chamber: Glycine max (Linn.) Merr. (Glycine 

 hispida Maxim.), Voandzeia subterranea Thou., Zea mays Linn., 

 Capsicum spp., Carica papaya Linn., Citrus maxima (Burm.) 

 Merr. {Citiixs decumana Linn.), Coffea arahica Linn., Anona 

 squumosa Linn., Hibiscus sabdariffa Linn., Nicotiana tabacum 

 Linn., SaccJiarum officinarum Linn., and the woody seedlings 

 Passiflora quadrangularis Linn., Lonchocarpus sp., and Caesal- 

 pinia sappan Linn. Seedlings only slightly attacked were Euge- 

 nia uni flora Linn, and Tamarindiis indica Linn. 



A coarse, dense mass of whitish mycelium is at first produced 

 in pure culture. Later whitish bodies of mycelium develop, 

 which enlarge and become hard brown sclerotial masses. The 

 sclerotial bodies are connected by fibrils. 



Control. — Since the disease is only severe during excessively 

 damp weather, in thick planting and where plants form a mat 

 over the ground, control consists in avoiding these conditions. 

 Planting should be done so as to escape the heavy rainy season. 

 Inasmuch as sclerotial bodies fall to the ground and remain alive 

 for a long period, crop rotation will have to be practiced. In 

 this crop rotation plants should be grown that do not form a 

 mat over the ground. Care should be taken that no sclerotial 

 bodies are sown with the seed. 



DOWNY MILDEW: PERONOSFORA 



Symptoms. — Light green blotches may be produced on the 

 leaves. These spots are due to the destruction of the chlorophyll 

 by the presence of the fungus. Young leaves are often wrinkled 

 because of the more rapid growth of the cells about the points 

 of infection. A light purplish to white downy growth is pro- 

 duced on the under surface of diseased leaves. 



Causal organism. — This purplish growth is made up of large 

 numbers of much-branched conidiophores at the tips of which 

 the spores are produced. The conidia are somewhat ovoid and 

 hyaline (fig. 18). 



Control. — Crop rotation should be practiced. 



