The Army Worm

Te Ao Hou, December 1962, Page 60

The Army Worm The army caterpillar which is often referred to as army worm is the caterpillar stage of a common native night-flying moth. It has often devastated crops in summer or early autumn and in a number of districts has severely damaged pasture on river flats, and swamp areas usually after summer flood followed by warm muggy weather. An attack by army caterpillar cannot be predicted with complete precision but we can tell when conditions are suitable for the pest and keep a close watch for it. Hay after mast, especially paspallum, newly sown pastures or cereal crops or land subject to summer flooding are all vulnerable to army worm infestation and should be watched very carefully with a view to making remedial measures. Caterpillars usually confine their feeding to sunny faces on hill country and shady faces are generally not depleted. They prefer plants of the grass family and the way in which they avoid patches of dominant clover pasture is really remarkable. Thus areas of pasture showing high fertility with plenty of clovers are usually not affected. If unchecked they may continue to feed well into June. Caterpillars can be controlled by spraying with either D.D.T. or Dieldrin and either killed off completely or prevented from moving on to fresh areas. Effective sprays applied by helicopter or aeroplane are 1 ½ pints of 15 per cent Dieldrin in 5–10 gallons of water (according to the lankness of the growth) where water is being used, or else 2 pints of 20 per cent D.D.T. in similar quantities of water per acre. Dieldrin is much quicker acting than D.D.T. but the latter is quite effective. A method of control is for a band of 50 to 60 feet in width to be sprayed with one pass of the aeroplane or helicopter and the perimeter of the advancing caterpillars. Half of the band is applied on the advancing caterpillars and half on the pastures ahead of them.