Changes in populations of the eyespot fungiTapesia yallundaeandT. acuformisunder different fungicide regimes in successive crops of winter wheat, 1984–2000

Abstract

Effects of regular treatments with the fungicides carbendazim and prochloraz applied to whole plots divided into subplots with different initial population mixtures of carbendazim-sensitive or carbendazim-resistant Tapesia yallundae or T. acuformis were studied in successive crops of winter wheat from 1984 / 85 to 1999 / 2000. In unsprayed and carbendazimsprayed whole plots, a stable coexistence of about 50% each of T. yallundae and T. acuformis developed within five seasons, but in whole plots sprayed with prochloraz or prochloraz plus carbendazim, the proportion of T. acuformis increased to > 80%. A discrete time difference equation model was derived from knowledge of the biology of eyespot and competition theory to describe the population changes. The model was fitted to the data from treatments where coexistence occurred [subplots in unsprayed (1985 -92) and carbendazim-sprayed (1985 -89) whole plots], using nonlinear least squares regression. The optimized value of the resource overlap coefficient was small, suggesting niche differences between the two species. Populations were nearly 100% carbendazim-resistant in carbendazim-sprayed whole plots by July 1985 (one season) and in whole plots sprayed with prochloraz plus carbendazim by July 1986 (two seasons). In prochloraz-sprayed whole plots, the proportion of carbendazim-resistant isolates decreased more rapidly than in unsprayed whole plots in the 1980s, but by July 1992 a shift in populations in unsprayed and prochloraz-sprayed whole plots towards predominantly carbendazim-resistant strains had occurred.

Inhibition of Efflux Transporter-Mediated Fungicide Resistance in Pyrenophora tritici-repentis by a Derivative of 4′-Hydroxyflavone and Enhancement of Fungicide Activity

“…1). That the fungicide application regimen affects the sensitivity of a population has been shown for the powdery mildews of barley and cucurbits, the wheat eyespot fungus Pseudocercosporella herpotrichoides, and the apple scab fungus Venturia inaequalis (2,7,19,22).…”

Occurrence of Eyespot on Winter Wheat in the Central-Southern Region of Poland

“…A prevalence of O. acuformis and restricted occurrence O. yallundae may be related to the common use of carbendazim for controlling eyespot (Bateman 2002;Bierman et al 2002;Birchmore et al 1992;Blein et al 2009;Dayer et al 1995;Głazek et al 1993;Korbas et al 1999;Smith et al 1994).…”

Resistance of winter wheat cultivars to eyespot and characterisation of causal agents of the disease

“…Previously Leroux and Gredt (1997) found that o. yallundae and o. acuformis co-occurred on up to 56% of the stems in a survey of wheat crops in France. Bierman et al (2002) described a stable coexistence of about 50% of both species in unsprayed and carbendazim sprayed plots for five seasons in the UK.…”