Queensland; Report of the Prickly-pear Travelling Commission 1912, November 1st-30th April 1914.
AbstractThe authors were appointed by the Queensland Government to visit countries in which prickly-pear is indigenous, or has become naturalised, for the purpose, inter alia, of looking for natural enemies which might be utilised for the destruction of this plant in Queensland. The report details the eleven species of prickly-pear at present naturalised in Queensland.
Prickly-pears were found to be little, if at all, adversely affected by insect enemies in the Mediterranean region, the Canary Islands, and Hawaii, and only to a slight extent in the West Indies and in most of the localities in South America which were visited. In Ceylon, India, and South Africa, only one species, Opuntia monocantha, was controlled in this way, the agent being in each case wild Cochineal insects [see this Review, Ser. A, ii, p. 440]. In the first two countries the attacks of Dactylopius (Coccus) confusus indicus had been so disastrous to the host plant that extermination had been practically brought about. The other naturalised species in India, 0. dillenii and 0. nigricans, and in Ceylon, 0. dillenii, were not attacked.
The most important insect enemies of cacti in America, including those in the United States [see this Review, Ser. A, i, p. 78] are discussed at length, and it is recommended that, for the time being, the following insects be introduced into Queensland: the Longicorn beetles, Monilema spp. and Coenopaeus palmeri; the weevil, Gerstaeckeria hubbardi; the moths, Melitara spp. and Mimorista flavidissimalis; the Coreid bugs, Chelinidea spp. and Narnia spp. ; the wild cochineal insects; Cecidomyia (Itonida) opuntiae and Asphondylia opuntiae., all from the United States; Cactoblastis (Zophodia) cactorum, Berg, (Argentine moth-borer) and another Phycitid, the Mendoza moth-borer, from the Argentine.
The Commission has already introduced into Queensland certain destructive wild cochineal insects, Dactylopius (Coccus) confusus indicus, from Ceylon, and D. confusus capensis, from South Africa. These have become established, and have maintained their destructive character at the Prickly-pear Experimental Station, and should exert a powerful influence in controlling 0. monocantha. Cactoblastis, which is destructive to a large number of prickly-pears, including several of the Queensland species, was also brought to that State, but most of the larvae have died.
The insects whose introduction is recommended may prove more harmful to cacti in Australia than in their native homes, where they are more or less controlled by predators and parasites, and therefore cannot exercise their full influence. It is consequently a matter of great importance that these parasites should have been eliminated before admission into Queensland. The necessity for provisions by the Queensland Government, so that any of these introduced insects may receive on arrival the proper care and attention needed for their propagation, is emphasised.
The true cochineal insects, Dactylopius coccus and its congeners, are very closely associated with the Cactaceae and will often only live on a particular species of prickly-pear. For example, D. coccus will only subsist on Opuntia cochinelifera, Miller, and will not attach itself to Nopalea cochinelifera, L., to which Dactylopius confusus newsteadi is confined. Similarly, D. confusus capensis, Green, is restricted, so far as is known, to 0, monocantha, [see this Review, Ser. A, ii, p. 440].
A number of other insects attack the prickly-pears, though they are not confined to them, including: Ceratitis capitata, Wied. ; the two mealy bugs, Pseudococcus obscurus, Essig, and Rhizococcus multispinosus, Kuhlg. ; the Cuban cactus Coccid, Palaeococcus sp. ; the Capsid bug, Stylopidea picta, Uhler; the Scarabaeid beetle, Trichochrous texanus, Lo Conté; the Calandrid root-borers, CactopJiagus spp. ; the cactus aphis, A. gossypii; and Tetranychus sp. Owing to the fact that these insects attack plants other than cactus, it is considered unwise to introduce them into Australia.
Those interested in the prickly-pear problem should consult this report in the original. The numerous illustrations are mostly from photographs and a list of over 400 references to the literature on the subject is appended.