AEROPLANES AND PESTS.

Otago Daily Times, Issue 20191, 31 August 1927, Page 6

AEROPLANES AND PESTS.

DUSTING EXPERIMENTS. Mr Amery prophesied at the Imperial Conference that the tsetse fly, so deadly', to cattle ,-and horses in Africa, would bo eradicated by aeroplane, and this (says Mr A. E. Blake in Science Progress for May) is a reminder of successful experiments in pest destruction bv the “dusking” of crops and trees by aeroplane. The new method, Mr Blake claims, has ended the fatalism with which growers have been accustomed to yield a proportion of the fruits of their labour to insects. In 1921 a grove of catalna trees near Dayton, Ohio, being infested with the catalpa sphinx, was dusted from an earoplana with lead arsenate. The machine's method was to fly some 50ft from tho tree on the windward side of the grove while a strong wind was blowing. Tho poison was fed from a hopper with •* capacity of 2001 b, attached to the side and rather below and to the side of the occupants, to avoid the danger of inhalation. The dust was distributed from the hopper from a small reel with spoonlike arms, which operated by a crank handle. Despite the rather primitive nature of the apparatus, the dusting was found to be effective for a depth of 60ft from the edge of the grove, and a mortality of 99 per cent, of the pest was revealed. Tlie next problem attacked was the problem of saving the cotton planters of the Southern States the £45,000,000 worth of cotton they lose annually to the weevil. In 1924, at the instance of Dr B. K. Goad, of Louisiana, a company, formed by the Huff-Daland Aeroplanes Company, began dusting on a commercial scale. The results exceeded expectation. In speea of operation the aeroplane was at least a hundred times as fast as the best muledrawrf* machine, which occupied a day in dusting 30 acres. The new method was much more economical in its consumption of chemicals, diverted none Of the workers from picking' or cultivation, and could be performed without delay immediately the state of the crops showed treatment to be desirable. The possibility of damaging the crops caused bv the passage of machines was obviated, and muddy land was powerless to hamper the work of the aeroplane as it does the ground machine. Even more important an advantage was the fact that the work was actually more efficiently performed. This was due to improvements in distributing mechanism. Essentially the apparatus consisted of special hoppers which deposited a thin stream of finely pulverised calcium arsenate into the current of air generated by the propeller and the drift of the aircraft, the velocity of which current had been raised to aomt 200 miles an hour by a funicular scoop. The down draught of the air screw then forced the powder down into the plants. The most interesting result was. however, one not expected. Until tho coming of the aeroplane dusting had to bo done at night or at some time when dew on the plants caused the powder to adhere. It was found, however, that the poison deposited bv aircraft adhered to the leaves and flowers when their surfaces were normally dry, and that the operation could therefore take place by daylight. This was due partly to tho force with which the powder was blown upon the crops, and partly to the manuteness of the powder particles, but chiefly to the fact that the dust particles had, in the process of delivery, become positively charged with electricity, and had come into contact with plants carrying a negative charge. Ground machines are now fitted with an electrical device. Two typos of ’plane have been constructed for crop dustim- according whether the area is small nr large. The larger typo flies at a height of sft tc 25ft above the crops, its speed of 80 to 90 miles an hour enabling it to dust at the rate of 75 acres a minute, in slightly overlapping strips some 2Ooft wide. Tie process has been applied to spruce trees, tobacco, peaches, potatoes, citrus, and sugar cane. In 1925 the use of the method spread tc Germany.