234 I'he Philippine Journal of Science isis 



LEAP spot: bakerophoma sacchaki diedicke 



Symptoms. — This is a very common and widely spread spot, 

 affecting the physiological function of the plants and thereby 

 undoubtedly lowering the sugar content of the cane. The base 

 of the leaf blade and the upper portion of the sheath on each 

 side of the ligule are affected. Spots are confined on the lower 

 leaf blade chiefly to the midrib. They are elongated, parallel 

 with the margin, from 1 to 4 millimeters in length, and have 

 a minute whitish center bordered with red or often with black. 

 The whitish center is usually rounded and slightly raised, being 

 made up of the spore-bearing body. The spots are found on 

 both surfaces of the midrib of the leaf, being more abundant 

 on the upper surface, and a few may be found outside of the 

 midrib. Spots on the upper portion of the leaf sheath are 

 similar to those on the leaf blade and are found on both sur- 

 faces. As a rule, they do not spread to the lower portion of the 

 sheath or far out on the blade (Plate XVI, fig. 4). 



Causal organism. — An oval 

 pycnidium is found in the center 

 of each spot. Within the pycni- 

 dia are numerous small, elong- 

 ated, hyaline, one-celled spores 



Fig. 28. Bakerophoma sacchari Diedicke. rfio" 28^ 



Various types of conidia (X _' ', ,_,, 



1,000). Control. — The disease is not 



serious enough to warrant any 

 special control. General sanitation methods will keep the disease 

 at a minimum. 



leaf spot: cercospora 



Symptoms. — A common leaf spotting, most injurious during 

 the rainy season, is caused by several species of this genus in 

 the Philippine Islands. Generally not a great deal of damage 

 is done to the cane. The vitality of plants is lowered, and the 

 green sugar-forming portion of the leaf is reduced, thereby 

 lowering the sugar content of the cane. Outer or older leaves 

 are most severely attacked, while the inner young leaves are 

 free from disease. Leaves infected by the common Cercospora 

 are at first spotted with an irregularly circular yellowish spot. 

 On the lower surface of the spot is a light-colored gray to 

 brownish dust made up of conidia and conidiophores. Spots, 

 as they grow older, become spotted with deep red to purple, or 

 the center becomes deep red to purple surrounded with yellow. 

 In extreme cases spots run together, enlarge, forming irregular, 

 long deep red to purple blotches usually bordered with yellow. 



