188 The Philippine Journal of Science 



Symptoms. — Die-back is common in poorly kept orchards and 

 appears, in the main, to be due to a lack of nutrition. The 

 symptoms are a gradual dying back of the branches, starting 

 from the tip. 



Causal organism. — No definite causal organism has been as- 

 signed. Many fungi are found on dead and dying twigs, in- 

 cluding the following: On Citru^s nobilis Lour.; Zignoella nobilis 

 Rehm., Cytospora aberrans Sacc, Eutypella citricola Speg., Hy- 

 poxylon atropurptireum Fr. (on coccids), Valsaria citri Rehm., 

 Massarina raimundoi Rehm., Tryblidiella rufula (Spreng.) 

 Sacc, Diaporthe citrincola Rehm., Diplodia aurantii Catt., and 

 Tryblidiella mindanaensis Henn ; and on Citrus maxima (Burm.) 

 Merr. (Citrus decumana Linn.) ; Eutypella citricola Speg. and. 

 Eutypella heteracantha Sacc. Growing on the latter fungus has 

 been observed another fungus, Nectria episphaeria (Tode.) Fr. 



Control. — Citrus culture in the Philippines is practiced in a 

 slipshod manner. Die-back may be largely avoided by the use 

 of correct culture methods. All dead and dying branches should 

 be pruned out and burned. 



EPIPHYTES: LORANTHUS PHILIPPENSIS CHAMISSO 



Symptoms. — Epiphytes are sometimes found growing on trees 

 in poorly kept plantations. They can be easily removed by 

 pruning. 



FRUIT ROT: LASIODIPLODIA THEOBROMAE (PAT.) GRIFFON ET MAUBLANC 



Symptoms. — A dry rot of citrus fruit may take place due to 

 the attacks of this common dry rot organism. Diseased fruits 

 are diaracterized by a shriveled, dry appearance and are covered 

 with a dense black sooty mass of spores. 



Causal organism. — The organism gains entrance into the fruit 

 through injuries. A series of pycnidia is produced just under 

 the surface of the fruit, and from there, through openings ex- 

 tending to the surface, the spores are expelled in large numbers. 

 The spores are, when immature, single-celled, hyaline, very 

 granular, oval bodies. Upon reaching maturity, they become 

 two-celled and dark brown. Germination takes place readily 

 within a few hours in water. The spores may germinate before 

 reaching the two-celled stage. The fungus grows well in pure 

 culture, producing, on potato agar, a heavy growth of dark 

 greenish to black mycelium. No spores have been observed in 

 these cultures. 



Control. — Care should be used in handling the fruit so as to 

 keep it free from injuries. 



