WAR ON LOCUSTS

Auckland Star, Volume LXXVI, Issue 84, 10 April 1945, Page 4

WAR ON LOCUSTS

INTERNATIONAL MOVE RESEARCH IN AUSTRALIA Lccusts living in luxury at Canberra are furnishing information that may be worth millions. Data on their doings help to protect Australian crops and pastures, and contribute to an international campaign against locust plagues. In rows of air-conditioned glass cages in a sunny laboratory they live lazily, eating and multiplying tc produce stock for experiments. Bunches of grass in glass jars provide both food and ornament. Twigs have been put in the cages so that the hoppers may climb to moult, out of reach of companions who ctherwise might eat them alive in the awkward defenceless moment between skins. Observation of their rate of development, length of life, fecundity arid mortality, under a wide range of controlled conditions, helps in understanding climatic, food and other factors conducive to locust plagues. So serious is the threat of the locust to great areas of Australia's best pastoral and wheat country that plague locust work is one of the few major civil entomological research projects carried on without interruption through the war. Dr. K. H. L. Key, at the Canberra headquarters of the Entomological Division of the Council for Scientific and Industrial Research, is head of the small team of workers who have been devoting their whole time to investigations in Queensland, New South Wales and Victoria for nine years. Laboratory work in Canberra is co-ordinated with field investigations all over the potential plague areas and with international locust research, centred in London. A field station in one of the worst plague outbreak areas, at Triangle, New South Wales, and regular reports from hundreds of country observers in a locust information service, organised by State Departments of Agriculture, bring in information to be analysed and co-ordinated at Canberra and in London. Milady Chortoicetes Hard-tamped soil in the glasswalled cages at Canberra simulates the sun-baked ground in which the Australian plague locust, Chortoicetes terminifera, lays her eggs. Milady Chortoicetes is equipped with a diamond-drill extensible abdomen by means of which, though she is only an inch and a half long, she is able to bore a hole three inches deep in the hard ground to accommodate 30 to 40 eggs. These egg-masses are drenched in a frothy fluid, which dries to. form "protective" capsules. Each female may make several layings in her lifetime. Under favourable conditions a new generation may be produced every two months and a half, though normally there are only three generations a year. In the plains where the plagues begin there may be from 200 to 800 egg holes to the square foot, over several acres. At only 300 holes to the square foot there would be 10,000 eggs to the square foot, or 400,000,000 eggs to the acre. After anything from a fortnight to many months, according to climatic conditions, the hoppers emerge, tiny miniatures of their parents, but wingless. They grow by a series of moulting stages to winged adulthood, two months from hatching. In the Warren-Condobolin-Forbes district of New South Wales in 193334 the December brood laid in eggbeds distributed over 500,000 acres. The next brood, hatched in February, laid its eggs in beds scattered over 3,000,000 acres. This brood damaged 33,000,000 acres of pastures and crops. Damage to pastures was £3,000,000 and to crops £1,000,000. That was a minor outbreak. In the great plagues hundreds of thousands of square miles have been infested. , . „ , In the 1934-35 plague the infestation area stretched from the Great Australian Bight through a great part of South Australia, over northwestern and northern Victoria, all over New South Wales, except a narrow coastal strip, and northward to central Queensland. Alarm over that outbreak led to the Commonwealth Government undertaking intensive locust research, through the C.S.I.R. in 1936. At that stage an effective method of poisoning wingless hopper swarms had been developed, but it was useless against flyers, which could take off on hops of 20 miles or more. There is evidence that, flying high, with tail winds, swarms of the Australian plague locust, in 1940, migrated up to 400 miles in two or three days at the most, from Queensland into north-eastern New South Wales. Small Ontbreak Areas Control would appear out of the question over Australia s great areas if it were not for one fact —the pldgues originate in comparatively small outbreak areas. Twenty known outbreak areas for the main plague species, Chortoicetes terminifera, have now been mapped, and several suspected areas have been plotted tentatively. All the known plagues have begun in the good pastoral areas in which these outbreak areas lie, and have spread coastward into the richer agricultural lands, particularly where there are no timber belts in the way. Since 1939 a field research worker and two or three assistants, at Trangie, in the middle of one of the worst outbreak areas, have been observing locusts' behaviour and features of soil, vegetation and climate, which make the outbreak areas specially suitable breeding grounds. Research has shown that to maintain a high population or enable it to increase to swarming density, vegetation such as tussock grass must be handy to the bare eggpatches, to give shelter to the partgrown and adult hoppers. This sort of pasture is produced mostly on selfmulching soil where the .surface cracks and flakes when dry.

Now that the outbreak areas are known and potential areas can be located readily, the next step is to devise methods of management of the pastoral country in which they occur to render them unsuitable for locust breeding. It happens that wind erosion, scouring out light red soil country, bares flat patches of hard subsoil suitable for egg-beds, while other areas grow tufty grass to shelter hatched hoppers. Regeneration of the country by approved erosion control methods should therefore help to eliminate breeding grounds. Dr. Key believes that if a method of working the outbreak areas acceptable to the grazier and unacceptable to the locust can be found, the frequency and severity of plagues can be reduced greatly. Other possibilities which may be tested by future research include control in the outbreak areas by spraying or dusting hopper breeding grounds from aircraft with the new insecticide DDT, or some other poison.