Plant Diseases May Be Blown Across Tasman

Press, Volume CII, Issue 30107, 16 April 1963, Page 13

Plant Diseases May Be Blown Across Tasman

Plant diseases could ’be spread from one country to another by methods other than the normal import and export of plant products, according to Dr. H. C. Smith, officer in charge of the Lincoln sub-station of the Plant Diseases Division of the Department of Scientific and Industrial Research. He was commenting on the recommendation of the trade ministers of Australia and New Zealand, Mr McEwen and Mr Marshall, that a joint technical committee should be set up to study plant and animal quarantine. Dr. Smith said it would be important to have on the committee someone who knew the present distribution of diseases of plant products and the significance of other means of introduction out-

side these normally associated with trade. At least three diseases of New Zealand wheat crops were believed to be carried from Australia by north-westerly winds.

Dr. Smith said there was definite evidence of new races of both leaf and stem rust being introduced from Australia on many occasions in the last 10 years. He had just received advice from Sydney University that a new race of rust which had attacked Hilgendorf (1931) wheat in Marlborough last season had originated in Australia.

An attempt would be made to confirm evidence that rust spores were blown across the Tasman. Dr. Smith said that with the collaboration with the Civil Aviation Administration and the Meteorological Department it was hoped later this year to carry out an aerial survey with the idea of picking up rust spores over the Tasman before they reached New Zealand. This would probably involve one or two special flights, the Meteorological Departmen" advising of the movement of large masses of air from Australia. These investigations were likely to be made about November.

It was also thought that the recent outbreaks of stinking smut or bunt in Central Otago could also be traced to Australia, with the smut being brought across the Tasman by the north-west winds in the same way as the rust. Stinking smut was one of the most serious diseases of wheat because it made the grain unfit for human consumption. Dr. Smith said he also believed that Australia was the likely source of barley yelow dwarf virus in New Zealand wheat crops. The cereal aphides which carry the virus, were known to be very widely distributed at high altitudes and ‘ could quite easily be blown across . the Tasman, There was no evidence that apy of the native grasses in New Zealand carried the virus, nor was it thought that the cereal aphis was a native of this country. There were also many diseases present in countries which were not officially recognised by the government agencies administering quarantine regulations. For instance, in Australia, until at least quite recently, it was still being maintained that that country did not have powdery scab of potatoes, and this was one of the reasons for Australia rejecting importations of New Zealand potatoes unless they were ‘horoughly washed, whereas the disease had been seen on potatoes on sale in Australia and several state departments had recognised the existence of the disease.

There were almost no diseases New Zealand had which Australia did not have also, said Dr. Smith, but one of the main dangers for New Zealand from Australia was Mediterranean fruit fly.