REVIEW MADE OF VIRUS TRIALS

Press, Volume CII, Issue 30094, 30 March 1963, Page 6

REVIEW MADE OF VIRUS TRIALS

AN evaluation of trials >r control of yellow dwarf virus in wheat last season and recommendations for the control of aphides which carry the virus were made at a meeting held at he Crop Research Division of the Department of Scientific and Industrial Research at Lincoln this week. The meeting was called by Dr. H. C. Smith, officer in charge of the Lincoln substation of the Plant Diseases Division of the D.5.1.R., to bring together all those engaged on work on the virus and to co-ordinate their activities. Representatives of the Entomology. Crop Research and Plant Diseases Divisions of» the the Department i of Agriculture from Palmers- J ton North, Christchurch and J Timaru and chemical • firms ; and spraying specialists from « Wellington and Christchurch . were present. I Dr. Smith said that the re-; suits of 21 field trials in ; Hawke’s Bay, the Manawatu,; North Canterbury and South j Canterbury ha*’ been de- j scribed and discussed. The J average increase in yield over J these trials was 13 bushels to ’ the acre which represented a ; very economic return for the j cost of one application of' systemic spray. J It was evident from these J trials that there was little; difference in efficiency be-» tween different chemicals ap- • plied at standard rates at the « right time. There was also; no benefit from g—at spray ;

applications unless there was aphis reinfestation, which occurred in only one trial at Lincoln. The results of a survey of farm crops from Waiau to Methven had been presented with information on the extent of aphis infestation, subsequent virus infection and yield. These results had confirmed the importance of early examination for aphides and the seriousness of losses which might occur even if very few aphides were present The survey also showed

thai'-some crops could be free anti— rgmain free of aphides and virus even in districts which had a high level of aphis infestation. There had been no evidence of any benefit from spraying where aphides were not present. The meeting had unanimously approved the following recommendations: (1) Autumn - sown crops should be examined frequently from May until September for aphis infestation. (2> If any aphides were present, the crop should be sprayed for control of aphides during the period from early July to midSeptember with an organophosphate systemic insecticide at a standard rate. This recommendation would enable maximum returns to be obtained from virus control. but later spraying from mid-September until midOctober still gave a good measure of control with increases in yield between six and 14 bushels to the acre. Too early spraying before early July was not recommended because late aphis flights might enter crops up until late in June. The Department of Agriculture is proposing to carry out extensive trials in the coming season so that recommendations can be made for spring-sown crops and for other districts.