THE ANTHRACNOSES OF CITRUS FRUITS, MANGO AND AVOCADO

Abstract

(1) Colletotrichum glocosporioides Penz. appears to be the cause of the anthracnose diseases of mango, orange, grapefruit, lemon, avocado, and sometimes of lime. (2) Lime wither-tip may be caused by either G. gloeosporioides or Glocosporium limetticolum Clausen. (3) Collelotrichum gloeosporioides Penz. frequently causes spotting of lime blossoms and the wither-tip. It is also the cause of the spots on lime thorns. The latter is demonstrated by cultures L 9- L, 13, inclusive, which behaved like other G. gloeosporioides cultures and very distinct from cultures of G. limetticolum. (4) Glocosporium limetticolum Clausen is the cause of wither-tip· ancl leaf spot of limes. (5) G. limetticolum appears to be the only cause of fruit canker or fruit spot of limes. (6) Under artificial conditions the various cultures of G. gloeosporioides and G. limetticolum exhibit distinct cultural characteristics. (7) Cultures from the avocado differ somewhat from cultures obtained from other hosts in cultural characteristics. The difference may not furnish enough evidence for their separation into a new species. (8) There are such differences between most cultures from the lime and all cultures from the other hosts that Clausen's (5) separation of the former into a distinct species appears to be justified. (9) The four most salient growth characters in which cultures of C. gloeosporioides varied from cultures of G. limetticolum or such cultures among themselves are: (a) size, number, and arrangement of acervuli; (b) color of acervuli and substratum; (c) character of aerial mycelium; (d) size of colonies. (10) C. gloeosporioides can resist slightly more acid or alkaline concentrations than G. limetticolum. (11) Setae are occasionally present in C. gloeosporioides and absent in G. limetticolum. (12) Variation in spore size is induced by the culture medium. (13) There is great morphological similarity between G. limetticolum and C. gloeosporioides. (14) Environment induces variation in form and shape of spores. (15) The character of conidia appears to be rather uncertain for distinguishing between Gloeosporium limetticolum gloeosporioides