INSECT PESTS.

Otago Witness, Issue 3774, 13 July 1926, Page 77

INSECT PESTS.

HOW TO CONTROL THEM. A decidedly interesting chat, illustrated by many lantern slides, was given by Mr D. Miller, Government Entomologist, to members of the Wellington Horticultural Society at itg annual meeting on the subject of “Insect Pests of the Garden and How to Control Them” (reports the Evening Post). It was a mistake to think that all insects were pests, said Mr Miller; each had some useful purpose to perform, and insects became pests only when they interfered with man’s agricultural and horticultural products. Since New Zealand was largely placed under cultivation many of the native insects had turned to man’s products, but only 29 per cent, of the pests which worried the gardener and the farmer were natives, and the remaining 71 per cent, had been introduced in one way or another, chiefly from Europe. Referring to individual pests, Mr Miller said that the best means, of control in the case of well-known grass-grub was to ensure strongly growing plants, since these were less liable to damage from the grub than weaker plants. A thorough rolling also assisted by compacting the surface, which in areas which were badly attacked became characteristically spongy. Turning up and resowing was really a waste of time, for that did not kill the grubs. Starlings and sparrows killed many grass grubs, and a natural insect enemy, the robber fly, both as grub and as mature insect, also assisted in keeping the grub down. The “subterranean grass grub,” another native, was also described; the Government was at present carrying out experiments for the control of this pest, and hoped to be able to announce the selection of a suitable insecticide by next spring. The “cut-worm” caterpillar, so called from its habit of nipping off young plants, could be kept under control by the use of poisoned bran (treacle and paris green) and by clean gardening—i.e., the removal of weeds and waste growth, and winter tilling, these latter means being of very real importance in all gardening and farming. The out-worm had numerous natural insect enemies. The well-known “magpie” moth and its grub, “the woolly bear,” was fairly well controlled by the use of arsenate of lead, used in the spring and early summer. The “diamond back” moth, which ate out cabbage and turnip leaves, could also be controlled by the use of arsenate of lead, commencing in the earlv spring. A poisoned spray would not kill the cabbage aphis, but a contact spray was effective. Similarly the “thrips” pest was best controlled by a nicotine contact spray. Neither poison nor contact spray was effective against “mealy bug,” but the Government was assisting in its control by the breeding and release of a particular lady-bird. Eel-worm, which attacked bulbs, tomatoes, and many other plants, was difficult of control, and really the only successful method was by means of steam sterilisation, or by hot water, up to about 140 degrees, where only the small quantities of soil were^einfl^doajAjvjth.