RAGWORT ENEMY

New Zealand Herald, Volume LXXI, Issue 21911, 21 September 1934, Page 8

RAGWORT ENEMY

FLY FROM ABERDEEN VERY USEFUL PARASITE WORK AT CAWTHRON INSTITUTE ; A wee fly from Aberdeen with a greedy taste for ragwort is expected by scientists ultimately to rid New Zealand of this troublesome weed. It is a parasite, and takes the easiest way to multiply and nourish its kind. Attracted by the flower of the ragwort, it lays its eggs therein, and the maggots live on the seeds. A correspondent of the Dominion says that such is one t>f innumerable experiments now being carried out by the Cawthron Institute under the supervision of Dr. D. Miller, chief of the entomological department. The first scientific onslaught against ragwort by entomological means was •with the caterpillar of the cinnabar moth; its attack did not prove sufficiently effective, since only one brood could be produced each season. The experiment has been discarded, and the Cawthron Institute's experts are now engaged upon establishing another parasitic insect, which promises to be extremely effective. The Aberdonian parasite is like a miniature house fly. It produces more than one brood, during the flowering j period of ragwort and statistics compiled by experts at the Farnham Koyal Laboratory, in Kent, show that 111 tugland the ) insect, in spite of beinc checked by its own parasites, is capable of destroying 70 per cent of raewort seeds in every head of flowers infested. In the absence of its own control parasites in New Zealand, laboratory experience indicates that here it will maintain 100 per cent destruction of ragwort seeds. Large supplies of the parasites will arrive soon from Farnham for liberation in New Zealand. At the quarantined insectaries in Nelson ragwort is cultivated both in outdoor plots and in a heated glasshouse, but, oddly enough, while the nursed plants make rapid growth almost to giant proportions, the date of flowering cannot be hastened. Plants within and without flower always at the same time. The "ragwort fly" is stated to be not a pest to man or beast.