XIII, A. 4 Reinking: Philippine Economic-Plant Diseases 205 



itself evident by the production of numerous, small black specks 

 on the under surface of the leaves. Serious damage may be 

 produced. 



Causal organism. — The pycnidia are brown, with conspicuous 

 wall markings, and they bear spines. Conidia are elongate, 

 somewhat tapering, often curved, five- to seven-celled, and 

 hyaline. 



Control. — Crop rotation should be practiced. 



BLIGHT : RHIZOCTONIA 



Symptoms. — During the rainy season entire fields may be 

 wiped out, due to this common soil fungus (Plate IX, fig. 1). 

 The disease is most severe in close plantings. Soy beans are 

 not the only plants attacked. All other beans and apparently 

 every plant growing in a matted condition may be attacked. 

 Aside from being found on beans, the disease has been observed 

 on African peanuts, Voandzeia subterranea Thou., and on weeds 

 growing among infected plants. Beans and other plants that 

 can be grown on trellises, so as to keep them off the ground, 

 and plants grown where they are not crowded, thereby per- 

 mitting of sufficient aeration, are less subject to the disease. 



Stems, leaves, and pods are all severely affected. The disease 

 starts from the ground, growing up the older hardy stem to 

 the tender portions or attacking the tender portions directly 

 if they touch the ground. The mycelium of the fungus can be 

 easily seen growing over the plants in a whitish mass and 

 spreading from plant to plant. Infected leaves are at first some- 

 what yellowed in blotches, and gradually they turn black and 

 disintegrate into a soft mass. Diseased plants touching healthy 

 plants will afford a means of spread. From infected leaves the 

 disease spreads to the tender stems and even to the more mature 

 stems, causing them to decay and to turn into a watery 

 mass. As the leaves and stems disintegrate, and especially dur- 

 ing drier weather, countless numbers of sclerotial bodies are 

 produced (Plate IX, fig. 3). These sclerotial bodies at first are 

 white and soft, but soon turn brown and hard. They are some- 

 times roughly spherical, from 1 to 3 millimeters in diameter, 

 or tney may be somewhat flattened and elongated, often 6 milli- 

 meters in length (Plate X, fig. 3). The diseased leaves and 

 sclerotial bodies fall to the ground, whence the latter produce 

 mycelia during favorable weather and attack plants as before 

 described. The disease is not severe during the dry season nor 

 during the drier weather in the rainy season. It spreads with 

 remarkable rapidity during damp weather. 



