Increases in wheat yield on limed soil after reduction of take-all by fungicide application and crop rotation

Summary. The severity of take-all, caused by Gaeumannomyces graminis var. tritici, was measured with lime, rotation and flutriafol treatments in a long-term field experiment. The incidence of eyespot lesions caused by Pseudocercosporella herpotrichoides was also measured. Flutriafol reduced the number of plants with deadheads or no heads and resulted in 12-60% more grain yield. However flutriafol had no effect on the number of plants with eyespot lesions. The number of plants with deadheads or no heads was highest (50-53%) on the wheat which was a third consecutive crop and on soil which had been amended with 2.5 and 5.0 t/ha lime. Sowing wheat after a subterranean clover based pasture considerably reduced the number of deadheads. Control of annual grasses in the pasture by spraytopping further reduced deadheads and with this treatment and at nil and low lime there were 2-7% deadheads. The percentage of plants with eyespot lesions was higher with the continuous cropped wheat. Lime increased grain yield only where the disease incidence was low but had no effect on the percentage of eyespot lesions. This work demonstrates the importance of crop rotation for disease control, particularly where soils are limed to amend severe soil acidity; the value of controlling annual grasses in pasture in the year preceding wheat cropping; and the potential of fungicide treatment as a practical means for controlling take-all in field grown wheat.