Take-all of wheat as affected by tillage and wheat-soybean doublecropping

Abstract

The effects of tillage and wheat-soybean doublecropping on take-all, caused by Gaeumannomyces graminis var. tritici. were examined during 1983–1985. Take-all incidence and disease severity (the percentage of roots with symptoms) were significantly greater in 1984 and 1985 in plots with conventional tillage compared to plots having no tillage (direct drilling). This increase in take-all with conventional tillage was also reflected in 1985 as an increase in the proportion of whiteheads. Each measure of disease (disease incidence, disease severity and percent whiteheads) was significantly greater under conventional tillage when the 3 yr were combined for analysis of variance. Take-all incidence and severity were not affected by doublecropping wheat with soybean when compared with wheat monocropping. No differences in the amount of buried wheat residue in the upper 15 cm were found between the two tillage systems. The implications of the rate of residue decomposition under the two tillage systems to inoculum potential are discussed. G. graminis var. graminis was isolated from soybean pods in 1983 but not in 1984. Isolates of G. graminis var. graminis were not pathogenic to wheat. G. graminis var. tritici was never isolated from soybean pods, leaves or roots.