POISONING PRICKLY PEAR. 
Relatively few of the pear plants had been killed outright by the poison so 
as to show no signs of growth in any part of the plant. 
The great bulk of the plants had completely collapsed, but were showing green 
shoots plentifully from many segments; green shoots were common from the 
“bulb,” and seedlings were springing up among the dried or semi-dried segments. 
A considerable number of pear plants were only slightly affected by the poison, 
the plant still standing with merely the outside skin covered with a yellowish, 
corky layer. These plants had either not been sprayed or only very lightly 
sprayed, or the poison had been washed off by rain before it had time to penetrate. 
In any case, they are very much alive, and the corky layer will largely protect 
them from further spraying. The presence of those plants will render the task 
of burning-off a difficult one. 
Cost of Clearing.—According to the contract, to “ kill by poison and clear off 
by fire the pear” on the 100 acres is to cost £700. 
Tire labourers are being paid £3 10s. per week. There have been from six to 
ten men employed for over two months in poisoning work. There are still 30 
acres to be poisoned, and the work of felling the scrub and burning-off and 
clearing up odd pear has still to be done. It is obvious that the Cactus Hstates 
Limited is not going to make much profit on this contract. 
Conclusion—As the so-called dense pear in this paddock is not nearly so 
dense as in many other districts, we are convinced that poisoning, as carried out 
by the Cactus Estates Limited, is much too costly to be considered as an 
economically possible means of clearing off pear of even medium density. 
STATEMENT OF THE GENERAL PROBLEM. . 
The results of the visit which we have paid to Umbercollie Station confirm 
in a striking manner the conclusions that we had formerly arrived at as members 
of the Board of Advice on Prickly Pear Destruction, and we consider that it 
will not be out of place to recapitulate briefly these conclusions. 
In considering the possibility of eradicating prickly pear it is necessary to 
classify the infested areas into at least three classes, each of which presents its 
own definite problems. 
The first class consists of heavily and moderately infested areas, mostly of 
poor agricultural but good grazing value. This group consisted a few years 
ago of areas each centering around a more or less definite area of infestation. 
‘These areas are now tending towards coalescence so as to threaten the great bulk: 
of the pastoral lands of the State. They now cover enormous areas. 
We are definitely of the opinion that it is impossible to treat this class of 
country economically by means of poison. This conclusion is based on the 
information at our disposal, and by the results of about 10,000 plot experiments 
carried out under the auspices of the Board of Advice on Prickly Pear Destruc- 
tion in Queensland. We consider that settlement under present conditions is 
powerless to cope with this class of country, which will be cleared or controlled, 
if at all, only by the discovery and utilization of natural enemies of the pest. 
This method has already been used with conspicuous success by the introduc- 
tion of the Wild Cochineal Insect, which has practically exterminated a large 
area of Monocantha Pear. Unfortunately, this insect will not attack any other 
variety of pest pear in Queensland, 
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