xm. 



However, there are a good number of Cactus insects that in their feeding 

 habits are not invariably confined to the Prickly-pears as is known from actual 

 observation or as may be inferred on reasonable grounds. Amongst these may 

 be mentioned the fruit fly — Ceratitis capitata, Wied. ; the Mealy Bugs Pseudo- 

 coccus obscurus, Essig. ; Rhizococcus muUi-spinosus, Kuhlg ; the Cuban Cactus 

 Coccid PalcBococcus, Sp. ; the Plant Bug— Stylopidia picta, Uhler ; the blossom- 

 injuring Beetle-^Trichochrous texanus, Le Conte ; the Calandrid root-borers 

 Cactophagus, spp. ; • the Cactus Aphis— ^. gossypii, the Cactus Red Spider— 

 Tetranychus, sp., &c. 



Now with regard to these three categories under which the Cactus- 

 injuring insects may be distinguished, we are of opinion that those embraced 

 in the first and second may with perfect safety be introduced into Australia ; 

 whereas those included in the last division should be rigorously excluded. 



No entomologist consulted with regard to this matter has expressed a 

 different opinion, except a distinguished Australian one who has pronounced 

 strongly against the introduction, on any consideration, of any plant-eating 

 insect for such work as is here contemplated. 



The experience of the Hawaiian Islands in subduing Lantana, has shown 

 that in certain cases plant-eating insects may be advantageously introduced 

 for weed destruction without detriment in any way to other vegetation. This 

 we have been able to confirm by personal inquiry. Moreover, we do not know 

 of any destructive insect of exotic origin accidentally or ignorantly introduced 

 here or elsewhere, whose destructiveness evinced in its new home, could not 

 have been anticipated from a consideration of its habits in its country of 

 origin. 



C. Disease. 



As a result of its investigations the Commission is led to conclude that 

 disease does not play a very important part in checking the spread of prickly- 

 pear when growing under natural conditions. However, we have seen and 

 studied a number of maladies caused by parasitic agency, as well as others 

 due to unsuitable environment, including climatic conditions. The latter 

 are of no importance from the point of view of our inquiry, and moreover, some 

 of them are already present in Queensland. 



There is apparently only one disease which the Commission regards as 

 being of sufficient value to warrant its introduction. This is the " anthracnose," 

 " shot hole," or "black rot" malady, caused by a fungus Gloeosporium lunatum, 

 E. and E. Ordinarily this organism has but little effect on the plant, but under 

 conditions such as obtain on warm moist days it causes a considerable and 

 rapid destruction of young segments, while older joints previously infected, 

 may also succumb to the " black rot " conditions set up. Cultm-es were brought 

 to Queensland by the Commission and handed over to the Dulacca Experimental 

 Station. 



In the Argentine Republic there is a very serious disease, " the white 

 rot" caused by a fungus Sclerotium (or Sclerotinia) opuntiarum, Speg., which 

 brings about the destruction of joints and stems of various cacti. As the habits 

 of this parasite are not sufficiently known the Commission does not, for the 

 present, recommend its introduction. 



There are other parasitic diseases known in the West Indies, United 

 States, Mexico, and the Mediterranean region, but their effects are not of much 

 importance in controlling the spread of prickly-pear. 



