PRICKLY PEAR PEST.

New Zealand Herald, Volume L, Issue 15482, 13 December 1913, Page 9

PRICKLY PEAR PEST.

DIFFUSION OF POISONOUS GAS. [FROM OUR OWN CORRESPONDENT.] Sydney, December 6. A novel scheme for getting rid of the prickly pear pest in Queensland has been propounded by Mr. Oliver C. Roberts, an American chemist who came to Australia about two years ago, and has been carrying on experiments at Dulacca, near Roma, about 250 miles west from Brisbane, for the past six months. Mr. Roberts has obtained a grant of 100,000 acres of land that, being thickly infested with pear, is regarded as being of no value. If he clears this, and he is confident of being able to do so, it becomes his own property, free. A certain measure of success has been obtained by his method of treatment, which is through the diffusion of a poisonous gas into the air, and the settling of the poison on the prickly pear plants in such a degree as to kill them. The poison is arsenic trichloride. It is raporised by. Are in a boiler placed in the midst of a pear patch, and the vapour is discharged. Being slightly heavier than "air, the vapour settles gradually, and condenses on the pear, penetrates the pores, gets into the circulatory system, and kills the plants from root to top. It condenses exclusively on the pea* says Mr. Roberts, because the pear contains so much moisture that its temperature is several degrees lower than that of the atmosphere. If the gas were diffused in wet weather there would be no such selection, and grass and scrub would stand equal chance of destruction. Consequently, the treatment must be' applied only in dry", warm weather. If that precaution be , taken, the inventor claims, nothing will be injured but prickly pear, and that w«, by a diffusion for about eight hours daily, be destroyed in about a fortnight. One boiler or cauldron will cover an area of about a square mile of country. The cost of treatment is about 15s an "acre. If the inventor succeeds, he will certainly be a benefactor in Quensltnd, where, according to Government estimates, over 15,008,000 acres of land is infested with the pest. The yearly spread of prickly pear is at the rate of about 1,000,000 acres. ■ >