X94 'rhe Philippine Journal of Science i9i8 



slopes of Mount Banahao, where it is very damp. The trees are 

 also planted too thickly. Both these factors are favorable to the 

 development and spread of the disease. 



Causal organism. — Microscopic examination of diseased tis- 

 sues taken from typical young cases of bud rot showed no evi- 

 dence of mycelium, but an abundance of bacteria. Diseased 

 pieces collected under sterile conditions in the field and placed 

 immediately into sterile vials developed no fungi; however, they 

 were completely invaded with bacteria. Many fungi would de- 

 velop from older diseased portions when placed in a moist 

 chamber, but under no conditions was one specific organism 

 always produced. 



Careful inspection was made of over thirty typical cases of 

 diseased trees. These trees were cut down and the bud opened 

 for observation. In all cases the disease appeared to be due 

 to bacteria. Isolations were made from sixteen different typical 

 cases. 



Cultures were obtained by cutting and plating out, under 

 sterile conditions, small pieces from all parts of infected trees, 

 from the tip of the unfolded infected leaves down to the growing 

 point and into the wood below. Poured plates from these cul- 

 tures showed that in the majority of cases a mixed culture of 

 bacteria was present. In very young cases of infection, however, 

 only one organism is present. The latter cases are hard to 

 obtain, because saprophytic bacteria find a favorable place for 

 development in the infected portion, and they are soon washed 

 down into these parts. In order to prove the virulence of the 

 bacteria isolated, a large series of inoculations was carried out. 



These inoculations were made chiefly with seedling coconuts. 

 The plants were from 60 to 180 centimeters tall. They were 

 carefully prepared for inoculation by stripping off the outermost, 

 older leaves. Then the portion to be inoculated was washed with 

 mercuric bichloride, 1 to 1,000. With sterile scalpels, stabs were 

 made into the growing point, and the pure cultures of bacteria 

 were introduced. The injuries were then covered with paraffin. 

 Over two hundred inoculations have already been carried out in 

 this fashion and typical cases of bud rot produced (Plate VI, 

 figs. 5 and 6). The first inoculations were not repeatedly posi- 

 tive, because they were made outside during the excessively dry 

 season, under which condition the organism is not extremely 

 virulent. In later inoculations made in a specially constructed 

 damp chamber, the disease could be produced at will with the 

 correct organism. By this method all the saprophytic bacteria 

 were eliminated. Inoculations with fungi also proved negative. 



