DESTRUCTIVE INSECT

Manawatu Standard, Volume LII, Issue 49, 28 January 1932, Page 2

DESTRUCTIVE INSECT

WHITE-WINGED MENACE.; PARASITIC CONTROL SOUGHT. . A serious menace to cruciferous plants in New Zealand is stated to be carried by a white butterfly which, while appearing to be -harmless, is most destructive and has already caused havoc among' cabbages in some districts where, plants have been riddled in a very short time. ■ Pie ns rapae, as this winged enemy of plant life is called, is recognised. throughout the world as a pest, but only comparatively recently has it been introduced into New Zealand. Every endeavour is now being made to check its, growing ravages by effective parasitic control, but these measures of protection are, as yet in the experimental stage, though good results are anticipated. The important work of dealing with this pest is now in the hands of Mr J. Muggeridge, B.Sc., the Government entomologist attached to the Plant Researoh Station at Palmerston North, and working in close collaboration with A. H. Cockayne. Carefully tended throughout ‘ their long journey to New Zealand, 2500 puparia of the small four-winged hymenopteron wasp, as yet in the cocoon stage, reached Palmerston North yesterday. l-fhev have been forwarded to New Zealand by the Imperial Institute of Entomology for parasitic control of the White butterfly pest. _ ... •„ ’ These small insects, it is stated, will not attack anything of economic - significance, and it is considered that their presence in this country will be wholly beneficial. ... .

READY FOR WAR.

War has been declared by scientific staffs upon' the destructive butterfly, and the wasps are being prepared for combat. The outcome of the encounter will be anxiously awaited. The wasps have proved to be a shccessful check upon the pest in the United States; The consignment which has reached this centre is the first, to be brought into New Zealand. It is safely housed in the insectary at the research area on the Massey College property, and steps are now being taken to propagate the wasps, after which they will be liberated in the affected districts. The white butterfly, which has been increasing in Hawke’s Bay, was first discovered at Napier in 1930, stated Mr Muggeridge to-day, and it appeared to be well established. It had not been investigated in the field, although specimens had been forwarded from Rotorua and Tauranga. Its ravages had been very serious among cabbages in Hawke’s Bay. It was problematical how it had reached New Zealand, but most likely it had been brought in some ship’s vegetable chamber from Hawaii. Tho time occupied in completing the life-cycle of the insect apparently varied considerably according to climatic conditions. The number of generations a year possible for the insect in New Zealand would vary a good deal according to locality. Cabbage, cauliflower, radish, 1 lettuce, water-cress, mustard, mignonette and nasturtium were some of its preferred food plants. The butterfly caused indiscrimate destruction of the tissues of the plants and the leaves of cahbages were left as mere skeletons. Pioris rapne could be controlled by the use of arsenical sprays. The main hopes of control, said Mr Muggeridge, centred in the effects of the yasps, which it was hoped would also attack the diamond-back moth, another big pest to cruciferous plants. The Imperial Institute of Entomology, he indicated, had also forwarded insects for parasitic control of the white fly which attacked tomatoes, but unfortunately they had not withstood the journey to New Zealand. Parasitic control in this instance also was being sought by a similar species of wasp to that introduced to deal with the white butterfly. Surveys were made in New Zealand and information collated was sent to the Imperial. Institute which took upon itself the task of ■selecting suitable parasites for control measures. ,