XIII, A, 4 Reinking: Philippine Economic-Plant Diseases 179 



producing on potato agar a dense mass of sporangiophores with 

 their blackish sporangia. Inoculation experiments prove this 

 fungus to be highly parasitic. Young inflorescences on the 

 tree are completely covered with the black mass of spore-bearing 

 bodies three days after inoculation. The mycelium invades the 

 tissue with rhizoids and produces a soft rot. The disease spreads 

 rapidly during damp weather. 



Control. — All diseased inflorescences should be carefully picked 

 from the tree and the ground and destroyed. Care should be 

 taken not to scatter the spores. In severe cases spraying with 

 Bordeaux mixture may be practiced. 



Dying leaves of the jack fruit may be attacked by Diplodia 

 artocarpina Sacc. and Dichotomella areolata Sacc. 



BETA VULGARIS LINN. CHARD 

 LEAF spot: cercospora 



Symptoms. — The common leaf spot of the chard is often very 

 destructive. Leaves of Swiss chard may be entirely covered 

 with the characteristic spots. Spots when young are small and 

 brownish to black; as they get older, they become larger, some- 

 times increasing up to 5 millimeters in diameter. Older spots 

 are circular and brownish and may exhibit concentric rings, and 

 the very oldest spots have an ashen-gray center bordered with 

 a brownish ring. Spots may coalesce and cover nearly the entire 

 leaf surface (Plate II, fig. 3). 



Causal organism. — Conidiophores and conidia are produced 

 in abundance in the ashen-gray center of the spots. Conidia 

 are long, tapering, and hyaline ; conidiophores are yellowish and 

 in groups. The fungus grows readily in pure culture, producing 

 on potato agar a more or less feltlike mass of white fungus, 

 with a slight pinkish tinge. 



Control. — The most satisfactory control consists in the collec- 

 tion and the destruction of diseased leaves and in crop rotation. 



BRASSICA OLERACEA LINN. CABBAGE 



BLACK rot: pseudomonas campestris (pammel.) erw. smith 



Symptoms. — The disease is characterized by the yellowing of 

 the leaves at the margins and between the veins and the black- 

 ening of the veins. Cross sections of diseased petioles show 

 blackened fibrovascular bundles (Plate X, fig. 2). 



Causal organism. — Pure cultures of the bacteria indicate that 

 the organism is the same as that attacking cabbage in the 

 United States, whence it was undoubtedly introduced on seed. 



156254 8 



