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



183 



simple plating out methods. It is more fully discussed under 

 black rot of cacao pods. 



Control. — The fruit should be handled so as to avoid injuries^ 

 and it should be used before it gets overripe. 



LEAP rot: mycosphaerella caricae sydow 



Symptoms. — This is a common leaf spot which, at times, may 

 severely attack plants, causing a lack of vigor and a premature 

 dropping of the older leaves. Circular spots, from a few milli- 

 meters to a centimeter in diameter, are produced. Older spots 

 have an ashen-gray center surrounded by concentric light-brown 

 rings bordered with darker brown. In the center of the older 

 spots the minute black perithecia are produced. 



Causal organism. — The peri- 

 thecia are produced under the 

 epidermal layer. They are more 

 or less globular and brown with 

 a distinct netted wall marking. 

 An ostiolum is present at one 

 end of the sack, protruding 

 through the epidermal layer of 

 the leaf (fig. 8). The asci, 

 borne within, are elongated, 

 club-shaped bodies containing 

 typically eight " two-celled, hya- 

 line, vacuolated spores (fig. 8). 



Control. — Since this disease is 

 of minor importance, no specific 

 control measure need be prac- 

 ticed. The collection and burn- 

 ing of all fallen or badly dis- 

 eased leaves is beneficial in 

 checking the fungus. 



Fia. 8. 



Mycosphaerella caricae Syd. a, 

 perithecium (X 325) ; b, broken 

 perithecium showing production 

 of asci (X 325) ; c, ascus with 

 ascospores (X 325) ; d. aseo- 

 spores (X 325). 



POWDERY mildew: ERYSIPHACEAE 



Symptoms. — Under favorable weather conditions papaya seed- 

 lings may be covered with a white powdery mildew. The 

 disease is not severe. 



Causal organism. — Typical erysiphaceous conidia and conidio- 

 phores are produced. No perfect stage of the fungus has been 

 observed. 



Control. — The disease is seldom severe enough to warrant a 

 special control. Powdering plants with sulphur will check the 

 disease. 



