NOXIOUS WEEDS

Evening Post, Volume CVII, Issue 72, 28 March 1929, Page 13

NOXIOUS WEEDS

INDUSTRIOUS INSECTS

REPORTS ON PERFORMANCES

To a meeting of the Noxious- Weeds Research Committee of the Department of Scientific and Industrial Research, held on 2Gth March, Dr. D. Miller reported that a full scheme of co-opwation with the Parasite Zoo, established' by the Empire Marketing Board at Farnlnun Royal, England, had been arranged. Consi'cnmeiits of insects to attack gorse, ragwort, blackberry, and other weeds had been regularly received from Farnhain Royal. ,A schme of forest biological research had been prepared and was now receiving consideration by the Government. The object of the scheme was to provide an adequate mpans. for the protection of the Dominion's native forests and plantations against loss through the ravages of insects and fungi. The Tyria moth, which has been liberated in ragwort infested areas at Te Puke, Stratford, Nelson, and Southland, was establishing itself well. Particularly favourable reports had been received from Taranaki Altogether some half a million eggs had been distributed. It was too early yet to estimate the success that s

likely to attend the liberation of these ragwort destroying insects. This year's trials would, however, provide valuable in formation in respect to its capacity for enduring the New Zealand winter and the degree to which it was likely to be attacked by parasites. Steps were being taken in some of the infested ureas to arrange for the transference of the insect to other areas in the immediate vicinity. If successful, it was hoped to have greatly increased numbers of eggs available, next year for widespread distribution throughout all, ragwort infested areas of the Dominion.

In the trials conducted with the blackberry parasite, Cdroebus, at Nelson great difficulty had been experienced in getting this insect to breed properly in the large insectary. This insect's natural habitat was the hot, dry, sunny Mediterranean shore line of Southern France, and as it appeared that.conditions in the large insectary were too cool to permit its best development, it had become necessary to use artificial heat and light with those insects which had established themselves in blackberry roots so far. In consequence, small numbers only were available for experimentation, ' and as yet it • bad not been found possible to try out Coroebus on any but a small range of economic plants. In the adult stage the insect had attacked leaves of. raspberries. The insect's destructive work, however, was carried out in the larval stage, when it attacked blackberry stems, boring spiral tunnels downwards towards the roots. The gorse insect, Apion ulicis, had shown a remarkable loss of fertility when imported to New Zealand. Out of 38,000 pupae already imported some 16,000 insects had emerged, but from these. the New eZaland progeny had amounted to only 125. This showed the difficult that had been experienced • in acclimatising the insect in New Zealand. Gas analyses of the containing boxes were being made on arrival in New Zealand in an endeavour to ascertain if the amount of carbon dioxide present had exerted any influence upon the virility pf both Apion and Tyria. More hopeful results were being secured from the sub-station established recently on Flag Staff Hill, Dunedirr: Some 3000 Apions were being tried out there, and egg-laying was now proceeding in some 50 per cent, of the gorse pods in the specially enclosed insectaries. From sample tests made recently it would appear that the fertility of the females was increasing and had increased from CO to 80 per cent, between two inspections. It was decided to continue these tests and to conduct trials with the insect upon all economic plants likely to be attacked before any deicision to release was made. The singular difficulties attaching to the acclimatisation of Apion we're exceedingly puzzling. Work was still proceeding in connection with Piri Piri and Foxglove parasite, but no new developments had been recorded. The estimated expenditure for the coming year was considered and approved. The Cost of the investigations are diared by the Empire Marketing Board, Cawthron Institute, and the Department of Scientific and Industrial Research. £3000 is being expended upon the New Zaland investigations and £1000 in England.