CONTROL POSSIBLE

Nelson Evening Mail, Volume LXVI, 30 November 1933, Page 4

CONTROL POSSIBLE

RAGWORT AND PIRIPIRI NOXIOUS WEEDS RESEARCH (From “'The Mail’s” Parliamentary Reporter) WELLINGTON, 29th November. “The researches carried on into the biological control of noxious weeds in New Zealand during the past six years have brought to light many features of biological importance, and, in the face of many negative results, have resulted in showing that there is every possibility of two species of weeds—ragwort and piripiri—out of the four dealt with durum the researches, being successfully controlled, while a partial success is to he expected in the case of a third, jjorse.” states the annual report of the Department of Scientific and Industrial Research. During the period covered by the report—March, 1932, to March, 1933—the grant from the now defunct Empire Marketing Board, which had been made to New Zealand for the furtherance of the biological control of noxious weeds, expired. But an unexpended balance was utilised for prosecuting researches on a modified scale. At the end of March last funds for this work ceased altogether, hut as researches in relation to ragwort and piripiri had reached a critical stage and showed possibilities of giving positive results. Dr. D. Miller, entomologist of the Cawthron Institute, Nelson, made arrangements for continuing activities. During the year the major activities were confined ,to the work on the ragwort seed-fly (Pegohylemyia jacohaeae) and the piripiri saw-fly (Antholcus varinervis). In the ease of the former a very large consignment was received during November from Fnrnham Royal; so far it has been found that a fly will usually place only one egg in a head, and the maggot developing from the egg will destroy all the seeds in that head. The evidence gathered to date shows tile great possibilities of this fly as a check to the seeding of ragwort. With regard to the piripiri saw-fly, the season’s operntions"further confirm the importance of this insect as a factor in markedly reducing the burrs of the weed; in this alone the insect would play a. very important role, hut if it became sufficiently well established it would also act as an invaluable check to the whole plant. Although lack of funds prevented a field survey being made, it is believed that the gorse-seed weevil (Apion ulicis) is establishing jn the areas where it was liberated in Otago. Owing to the unseasonable flowering of gorse. in most parts of New Zealand, it is in the southern districts alone, where (lowering takes place in the summer, that the weevil will have an opportunity of actively checking the seeding of gorse. The utilisation of the Buprestid beetle (Coradius vubif against blackberry has been considered unsafe owing to the tendency of the beetle to attack the foliage of apple trees. Furthermore, though blackberry canes are heavily infested hv the larvae, it has been found that the’canes are capable of developing fresh shoots even from points within the region damaged by the insect.