PLANT RESEARCH

Evening Post, Volume CXX, Issue 111, 6 November 1935, Page 22

PLANT RESEARCH

WORK IN DOMINION

GREAT PROGRESS MADE

PRACTICAL TESTS

The Plant Research Station, Palmerston North, is a Government organisation administered by the Department of Agriculture in conjunction with the Department of Scientific and Industrial Research, both Departments contributing the finance for its upkeep. It represents an enlargement of the old biological section of the Department, and was transferred Irom Wellington to Palmerston North in 1928. It has temporary laboratories and offices in the town, and investigational and experimental areas on the Massey College farm. In addition, it has a branch area on the farm of the Canterbury Agricultural College at Lincoln. Although not officially connected with either Massey or Lincoln College it works in a very close association with those institutions, and also with the Wheat and Dairy Research Institute, The range of its activities is wide and comprises research and investigations into plant diseases and insect pests, research on grassland farming and arable farming . and many features of orchard practice. Probably its main feature is the fact thaf all its activities, although many are highly technical, are essentially connected with practical aspects in the improvement of primary production. Its work in disease control, in pasture improve-1

ment, in insect control, in improvement in manurial practice, in crop certification, and in seed testing are all exerting a powerful influence in agricultural development in New Zealand, an influence that its close association with the Fields Division of the Department of Agriculture can be made Dominionwide. THE WHITE BUTTERFLY. The entomological section of the Department of Agriculture deals with the control of various insect pests as they affect either plants or animals. The objects of this section are: (a) To provide an efficient entomological service for the benefit of the public, and (b) to help reduce the costs of production:by the application of entomological knowledge. As an example of work conducted by the section the following resume of the white butterfly problem is given. The white butterfly, an old world species of insect, was first noticed in this Dominion in 1930. How it reached here is problematical; most likely it was brought.here in some ship's vegetable chamber, from Hawaii, and accidentally got ashore when the ship' was in port at Napier. It soon became firmly established and spread with alarming rapidity, proving very destructive of farmers' crops, such as rape, chou moellier, swedes, and turnips, etc. The Department of Agriculture introduced two species of parasites from England to deal with it, namely, a larval and a pupal parasite. The latter—the pupal parasite, Pteromalus puparum—which was first released in 1933—has proved to be an outstanding success. In 1933, 10,812 of the above

parasites were liberated in Hawke's Bay, and in a subsequent examination of 415 butterfly pupae collected, 58 per cent, were found to be parasitised. In 1934 there was a noticeable reduction in butterflies around Maraekakaho, but elsewhere they increased and spread. Later in the same year 90 per cent, of 5000 butterfly pupae collected much further afield than the original place of liberation proved to be parasitised. The parasite had then spread over hundreds of square miles, extending as far as Alfredton, a distance of 82 miles. UNDER CONTROL. The early success of this parasite led the Department to concentrate on rearing large supplies of them for liberation far and wide during ;the 1934-35 season. Special methods and technique for rearing them had to be devised, but this proved quite successful, and close on one million parasites were reared, and distributed in the field. During the 1934-35 season the pest was virtually brought under control in Hawke's Bay. Parallel events have occurred in the Manawatu —a small supply of parasites having been liberated in 1934, resulted in H per cent, of the pupae collected being parasitised. At points outside of where the parasites were liberated 19,567 pupae were collected, and none of these was parasitised. During the 1934-35 season butterflies were very prevalent in the ManawatuMarton district, but the parasites already liberated were equal to the occasion, and o^ 21,881 butterfly pupae collected this past winter of 1935, no less than 20,940, or 96 per cent., were found to be parasitised. No doubt the white butterfly will always be with us, but the parasite has checked the widespread ruin that- inevitably would' have occurred in the most important of our forage crops— the brassicas. During the coming season the Department will have available a small

supply of parasites" ioi^liberation only in those areas where the parasite is known not to be established. The parasite responsible for the above good work is a small fourwinged insect, a bit smaller than, but, in a general way, not unlike a flying ant. This winged form lays its eggs in the butterfly chrysalid—commonly found on walls of houses, on fencing posts, amongst grass or weeds surrounding a crop, or on the leaves of the host plants—the eggs hatch out into small grubs which obtain their nourishment and complete their development by living on the contents of the chrysalid. From this stage they pass to a pupal or chrysalid stage, and thence again into the adult winged stage. In addition to the above, chemical methods of control are also being experimented with, and during the coming season, some important experiments in connection therewith should be concluded. Other important work with which the section is concerned is improvement in spray methods and technique for the more efficient control of insect pests and a consequent reduction in costs. Preliminary laboratory experiments carried out with 26 specially-prepared oils showed striking differences in the' killing powers of oils on the eggs- of two species of mites, viz., "Clover Mite" and "Red -Mite," both serious orchard pests. Quick.breaking unstable emulsions were found to be much more effective than were stable permanent emulsions made. with the | same oils. Detailed experiments are again at present under way,' from which it is expected that further valuable information will be obtained.