176 



The Philippine Journal of Science 



Septogloeum arachidis Rac. a, 

 cushionlike structure of conidio- 

 phores (X 350) ; b, germinatinpr 

 conidia (X 350) ; c, conidia 

 (X 350). 



brown. On the surface in the 

 grayish portion is produced a 

 black powdery mass. 



Causal organism. — This black 

 powdery mass is made up of 

 hyaline, many-celled tapering 

 conidia, which are produced on 

 brownish conidiophores. The 

 conidiophores are formed in 

 groups and are septate. 



Control. — Diseased plants 

 should not be allowed to accu- 

 mulate in the soil. Crop rota- 

 tion should be practiced. In 

 severe cases of infection, spray- 

 ing Bordeaux mixture will have 

 to be resorted to. 



ARACHIS HYPOGAEA LINN. PEANUT, MANI 

 LEAF spot: SEPTOGLOEUM ARACHIDIS RACIBORSKI 



Symptoms. — This well-known and widely distributed leaf spot 

 may be extremely destructive on certain varieties of peanuts. 

 It affects the lower leaves of the plant, and complete defoliation 

 of this portion may result. From the lower portions the disease 

 spreads to the upper leaves. The disease is most'severe during 

 damp weather, when both leaves and stems are attacked. Spots 

 on the leaves are usually circular, black to brown, with a yellowish 

 discoloration of the leaf tissue adjacent to the spot. The centers 

 of older spots, chiefly on the under leaf surface, are specked with 

 the raised masses of conidia and conidiophores. Spots on the 

 stem are similar, but are usually elongated lengthwise. Certain 

 varieties of peanuts show a marked degree of resistance. 



Caudal organism. — The more or less powdery, elevated bodies 

 on the under surface of the spot are cushionlike structures made 

 up of a mass of conidiophores and conidia (fig. 4). The elong- 

 ated spores are brown and usually consist of from three to four 

 cells. They germinate readily in water by the production of 

 germ tubes, most frequently from one of the end cells (fig. 4). 

 Inoculation experiments are easily carried out by spraying plants 

 with a spore suspension. Penetration into the tissue is by means 

 of the stomata (fig. 5). After gaining entrance, the mycelium 

 spreads in local spots throughout the leaf, causing the death of 

 the cells and the consequent browning of the tissue. The fungus 



