Effects of foliar sprays of azoxystrobin on take-all in wheat

Average percentages of winter wheat plants with severe take-all were decrea sed by up to half by azoxystrobin applied as foliar sprays in four field ex periments. Decreased take-all in three of the experiments was associated wi th increased grain yield but effects on other diseases may have contributed to these responses. Standard fungicide sprays were ineffective. The effect s differed, but not consistently, among different cultivars that were teste d in three of the experiments. One, two or three sprays of azoxystrobin or kresoxim-methyl, in autumn, spring or summer, were tested in the fourth exp eriment. Unlike azoxystrobin, kresoxim-methyl had no consistent effects but a smaller amount was applied. Two or three sprays of azoxystrobin were mor e effective than a single spray but their timing was unimportant. Such cont rol of a root disease by a foliar-applied fungicide is unusual but may help to explain some of the unexpectedly large yield responses to azoxystrobin that have been reported. This relatively broad-spectrum fungicide may have the potential to contribute to the practical management of take-all but fur ther research is needed to determine how best to exploit its effects consis tently.