94 PRESIDENTIAL ADDRESS. 
order to ascertain, amongst other things, whether there 
existed in those regions any natural enemies, either plant 
or animal, which were holding the cacti in check and which 
might be safely introduced into Queensland with a view 
to controlling the spread of prickly pear here without. 
themselves becoming a danger to other plant or animal 
life in this State. As a result of our inquiry it was found 
that there occurred in certain countries, e.g., Ceylon, India, 
United States and Argentina, formidable enemies capable 
of retarding the spread of, and in some cases actually 
exterminating, certain species of Cactacez, and that many 
of these were restricted in their dietary to this family of 
plants, sometimes even to one or two species of Opuntia. 
An account of the work of these organisms is con- 
tained in our report*, but I intend in this brief survey, 
to refer only to such as were brought, or sent, by us to- 
Australia. 
The parasitic fungus Gleosporium lunatum, E. & E..,. 
which under certain conditions of climate causes a “ shot. 
hole ” effect but which in moist warm weather produces 
a widespread rotting or “‘ black rot ”’ of the young cladodia. 
or “‘ joints,’’ was introduced in the form of cultures, but. 
the attempt to establish it in our State was unsuccessful. 
The insect enemies introduced comprised two forms. 
of a wild cochineal, Coccus indicus, Green, from India and 
Ceylon, C. confusus var. capensis, Green, from Cape 
Colony and a moth, Zophodia cactorum, Berg., from 
Argentina. The last named failed to establish itself as the 
larvae which reached Brisbane died before pupating. 
The wild cochineal insects, especially the more destruc- 
tive species, C. indicus, have become well established, 
the latter having been liberated in the vicinity of Bowen 
and Charters Towers in Northern Queensland, where 
Opuntia monacantha is prevalentt. It is gratifying to- 
*T. H. Johnston and H. Tryon. Report of the Prickly Pear Travel- 
ling Commission, Nov. 1912—April 1914. Govt. Printer, Brisbane, 1914. 
+ J. White-Haney lc., 1914 (1915), p. 82. See also article “ De- 
struction of Prickly Pear by the Cochineal Insect,’ Q’land Agri. Jour. 4, 
1915, p. 323. 
