172 The Philippine Journal of Science ma 



guard the interests of the thrifty and foresighted farmer who 

 does know how to spray and who puts his knowledge into prac- 

 tice. As it is, practically no spraying is carried on in the Islands. 

 This paper has been written in order to give some idea of 

 the prevalence of plant diseases, their causes, mode of attack, 

 plant hosts, amount of damage, and methods of control. While 

 the list of diseases is by no means complete and while it takes 

 into consideration primarily those diseases found in Laguna and 

 near-by provinces in Luzon, it will demonstrate that practically 

 all agricultural crops have their fungous enemies. Many of these 

 diseases are due to fungus species new to science. The con- 

 tribution of these new species has been largely due to the collec- 

 tions of Prof. C. F. Baker, professor of agronomy in the College 

 of Agriculture. 



ANANAS COMOSUS (LINN.) MERR. (A. SATIVUS SCHULTES F.). 

 PINEAPPLE 



LEAF spot: asterinella stuhlmanni (henn.) theissen 



Symptoms. — The lower leaves of the pineapple are frequently 

 and sometimes seriously attacked by this superficial leaf -spotting 

 fungus. The black mass of mycelium produces spots that extend 

 rapidly and often cover the entire leaf. Older spots are fre- 

 quently elevated, due to the shrinkage of the surrounding tissue, 

 and they have dark gray centers covered with minute black 

 specks, the perithecia. The fungus causes the premature death 

 of the lower older leaves. 



Causal organism. — The perithecia are usually seen with the 

 naked eye. They appear as minute black specks in the grayish 

 diseased portion. The asci within the perithecia are sack-shaped 

 bodies and usually contain eight ascospores. The latter are two- 

 celled and elongated, with a large vacuole in each cell. The 

 fungus is a superficial grower, but feeds on the cells by the 

 production of haustoria, and in this way it weakens the leaves. 



Control. — Sanitation methods are advisable, such as the collec- 

 tion and destruction of the older, badly diseased leaves. In 

 severe cases of infection crop rotation should be practiced. 



Lembosia hromeliacearum Rehm. is also found growing superfi- 

 cially on the living leaves, parasitizing them by the production 

 of haustoria. 



SOOTY MOLD 



Symptoms. — Black felty masses of a superficially growing fun- 

 gus may be produced on the under surfaces of leaves. The 



