Visit To D.S.I.R. At Lincoln By Farmers

Press, Volume C, Issue 29505, 5 May 1961, Page 8

Visit To D.S.I.R. At Lincoln By Farmers

The yellow dwarf cereal virus in wheat and current research work were the main points of interest for members of the Dominion Agriculture Section Council of Federated Farmers when they visited the Department of Scientific and Industrial Research centre at Lincoln yesterday. The party toured the different research divisions and trial areas and listened to a panel discussion on the yellow dwarf virus which caused much damage in the New Zealand wheat crop last season. The virus is carried by flights of aphids from old to new plants. The yellow dwarf virus attacked all cereal crops throughout the world, including maize and rice. Mr J. D. Allen, a plant pathologist of the plant diseases division, said. Grasses acted as a natural reservoir of the disease and only twitch and browntop appeared immune. Autumn infestation by aphids of young wheat crops produced heavy local patches of damage by the virus in the crop. In the spring the new flights of aphids spread from these to the rest of the crop. The spring flights sought the spring 'own crops.

Control could be by breeding a resistant variety of wheat—a difficult task, because there was no known source of resistant material: or by sowing after mid-May to early June to avoid the autumn aphid flight and having as much growth as possible before the spring flights. A third control measure was to spray insecticides on the aphids. "If the farmer can see aphids on the crop it is bad enough to warrant spraying,” he said. Dr. A. D. Thomson, a plant virologist in the division, said there appeared to be different strains of the yellow dwarf virus which would complicate any breeding programme aimed at resistance. The virus had probably been in New Zealand as long as wheat had been grown, said Mr L. G. Copp, senior plant breeder of the crop research division. He was fairly confident that it had been the cause of Cross Seven wheat failures in 1952.

At present’no source of resistant material for wheat breeding was known but there was a barley from Abyssinia which had a very high resistance and was being used for experiments in the United States. The whole of the crop research division's wheat collection is being tested for tolerance to the virus, he said. Other projects this year included spraying of the crops to kill aphids, early sowing with the expectation of heavy infestation and deliberate introduction of the disease to crops.

Aphids generally were dormant during the winter but in New Zealand the grey cabbage aphid, the wheat aphid and the green peach aphid continued their summer cycle throughout the year. While reproduction in the winter was slow there was a terrific upsurge in numbers in the spring, said Mr A. D. Lowe, an entomologist in the entomology division's sub-staDion. The cereal aphid in the spring migrated in flights to the succulent spring sown crops.

"In Canada there are six kinds of aphides capable of carrying the yellow dwarf virus but fortunately New Zealand has only one such aphid as yet.” he said. Work on lucerne varieties and diseases and research on field crops, including brassicas. was described to the council members by Mr T. P Palmer, a plant breeder of the crop research division.

Mr C. M. Driver, plant breeder of the division, spoke on recent work on potatoes and the development of new varieties and the control of diseases in commercial crops. The party also visited the botany division's new building.