RAGWORT SEED-FLY

Grey River Argus, 15 March 1940, Page 4

RAGWORT SEED-FLY

SCIENTIST’S OPINION. HAMILTON, March 12. The progress made in the experiments conducted to determine the value of the seed-fly in controlling ragwort was described in a statement by Dr. D/ Miller, assistant director and chief entomologist at the Cawthron Institute, Nelson. Dr. Miller said the observations so far showed that the insect was developing slowly in the field, but it had not yet reached a stage when an unqualified opinion could be expressed. “What we know of the possibilities of the fly is that, from our researches under control conditions. 100 per cent of the seeds in every flower head infested by the maggots will be destroyed,” Dr. Miller stated. “However, this does not mean that every flower head, or even a big proportion of them, will be destroyed eventually. We have yet to ascertain whether the fly will develop in the field to such an extent as to infest a sufficient number of flower heads to give an adequate control for practical purposes.

“The insect will not eradicate the weed. What is expected of it at the best is to control the seeding and so reduce the spread of ragwort from inaccessible places. Farmers must continue their control methods under farm practice to check the weed on lands accessible to farm management. Tire farmer must, not be encouraged to throw over his control efforts in the hope that the insect will act as an eradicating agent of the plant itself.

“Our first endeavour in liberating the fly,” Dr. Miller added, “is to establish it on as restricted an area as possible and thus give the insect a chance to build up a sufficient population in the field under New Zealand conditions to show whether it wifi come up to expectations and whether we will be justified in finally making mass rearings for wide scale liberations throughout the ragwort areas of the country.”