Timing of fungicide application for control of eyespot disease of winter wheat
1995
Jones, D.R.
A series of 23 field experiments was undertaken from 1984 to 1986 to investigate the optimum timing of foliar application of prochloraz for control of eyespot on winter wheat. The possibility of delaying the prochloraz application from GS31 to GS32-33 or GS37-39 as a means of reducing the overall number of fungicides required to optimize profitability was investigated in a further series of 24 experiments from 1987 to 1989. Applications of prochloraz between GS30 and GS32-33 were equally effective for eyespot control at most sites, although in one year treatment was less effective at GS32-33 than at GS31. Later applications, at GS37-39, were less consistent, although in some years they were as effective as applications between GS30 and GS33. Early February was the optimum time of prochloraz application on one very advanced crop which reached GS30 by the end of January. In the 1987-1989 experiments, prochloraz alone at GS37-39 was less effective than the best treatments for control of yellow rust and Septoria tritici. Treatments with three fungicide applications for control of these foliar diseases gave the highest yields at many sites but, except where their incidence was particularly high, treatments with one or two fungicide applications were often more cost-effective. Yield increases following fungicide treatment were associated with increases in thousand-grain weight and, at some sites, in specific weight. It was concluded that where there was a high risk of either eyespot or foliar disease specific fungicide applications were required for each, but where the disease risk was lower it was sometimes possible to control both with a single application.
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