PRICKLY PEAR

Waipa Post, Volume XXIV, Issue 1660, 8 September 1925, Page 6

PRICKLY PEAR

ERADICATION METHODS IN QUEENSLAND.

USE OF INSECTS. AND POISON

The first annual report of the Prickly Pear Land Commission of Queensland has been issued, and is rather a remarkable document, covering some 115 large pages. The commission assumed office in April, 1924, and since then has had control of the whole of the lands of Queensland infested with the pest. This area is approximately 51,500,000 acres, which is three times the size of Tasmania, and approximately the same as that of Victoria, or the combined areas of England, Scotland, and Wales. It extends from a 250miles base resting on the border of New South Wales, and gradually tapers northward to a forty-miles frontage in the vicinity of Mackay. There are two chemical poison agents recommended and distributed by the commission. One is arsenic pentoxide (which is sprayed in liquid form on to the pear, and is so powerful in its action that one-twelfth of an ounce will destroy one-hundredweight of pear, the cost to the landholder being a penny per ton of pear). In ten months from Ist September, 1924, to 30th June, 1925, the commission sold 75 tons of arsenic pentoxide to 3015 landholders. Arsenic pentoxide, however, is unable to penetrate the skin of tough old plants, and in order to deal with these the second tyjp of poison is used. This is Roberts’ pear poison, a specific containing 20 per cent arsenic pentoxide and 80 per cent of moderately concentrated sulphuric acid. The acid burns the outer tissues of the pear, and the arsenic pentoxide does the rest, completely destroying the plant. During the eleven months ended 30 th June last 515 tons of this specific were sold to 1630 purchasers. The amount paid by landholders to the commission for the poison at 30th June last was £28,445, and the quantities of poison distributed were sufficient to destroy over 3,500,000 tons of pear. Since the arsenic pentoxide has to be imported, the commission considered th,e question of local State manufacture, and decided against the proposal qs being too costly.

Prickly pear has also been eradicated by biological methods. Cochineal insects were first imported from India in 1912, and within a few years most of the pear of a particular type had been destroyed. This insect, however, attacked only the one type. Another type of cochineal insect was secured proviately from America. These insects were found to attack ordinary pear pests, but their usefulness was greatly hindered by the -mysterious appearance of ladybirds, which preyed on the insects. Biological methods are, however, not suited to eradicating ver yscattered pear. They are of tlie greatest use in the badly-infested and denser districts. The commission has distributed up to the end of June last 4206 cases of cochineal insects to 1554 landholders free of charge. Next summer season the commission intends to arrange for the wholesale distribution of insects throughout the whole of the pear districts, so that a maximum result may be achieved. The report gives no results, the opinion being expressed that it is too early to make a definite statement. But experience has proved that much good work will be done by the insects. The report is very definite, however, that both biological and chemical methods must be used to secure the best results. The commission undertook the clearing of special areas of Crown lands badly infested, and as a result several thousands of acres have been entirely freed from the pest. The total expenditure of this work was £1550. The commission subsidises local authorities in the matter of pest eradication on the basis of £2 for every £1 spent by the latter.

At 30th June £1261 had been paid in subsidies. The commission’s vote is £IOO,OOO a year, and last year £77,426 was spent, of which sum £28,448 came back from the sale of poisons. The commission is also a judicial body, which takes evidence regarding the adjustment of rents and tenures throughout the pear belt. At 30th June it had given 2300 decisions. The report further states that during the decade 1913 to 1923 prickly pear in Queensland spread over an additional area of 8,373,'278 acres, representing an annual average of 837,328 acres. Although the pear territory is defined as 51,500,000 acres, the latest official estimate of infestation is approximately 25,000,000 acres. If left to itself the pear is estimated to spread over all those parts of the State with an annual average rainfall exceeding 12 inches, and mostly falling within the summer months. If left unchecked the pest would infest one-half of the State in 25 years. The report expresses the advisability of co-ordination between the three prickly pear bodies, namely, those in Queensland and New South Wales and the Commonwealth Board. This co-ordination apparently does not yet exist. The report contains some striking photographs of the destructive influence of the pear in turning what were once splendid holdings into unproductive wildernesses.