Agronomic and meteorological factors affecting the severity of leaf blotch caused by Mycosphaerella graminicola in commercial wheat crops in England

Abstract

Factors affecting the severity of leaf blotch on the two upper leaves of wheat plants in crops at the milky ripe growth stage (GS 73-75) were investigated using survey data from 3513 randomly selected wheat crops sampled during 1985-1996. Year-to-year variation in disease severity was greater than spatial variability at county level, although both showed significant differences. The presence of disease above a 5% severity threshold was modelled using random effects logistic regression (Generalised Linear Mixed Model), which enabled risk variables measured at the field level to be combined with meteorological variables estimated at county level. The final model included terms for the fixed effects of disease resistance rating, date of sowing, high risk septoria periods in May and June, number of fungicide sprays and number of days with frost (£ -2°C) in November. The percentage of crops above the threshold decreased with later sowing, increased number of November frost days and increased number of fungicide sprays. In contrast, high risk septoria periods (rain splash events) in May and June showed a positive correlation with the percentage of crops above the threshold. There were benefits from using resistant cultivars. The model showed that a range of risk variables were of broadly equivalent importance in determining the development of leaf blotch. These risk variables should be integrated in any scheme designed to support fungicide use decisions.

The effects of soil tillage and crop rotation on the development of winter wheat leaf diseases

“…The conditions are especially important in the first half of May, during stem elongation, which is the crucial period of this disease's development. The importance of rain splash for the development of this disease is widely known, and different studies across the world have demonstrated this relationship (Gladders et al, 2001).…”

Wheat archive links long-term fungal pathogen population dynamics to air pollution

“…We compared the DNA data for each pathogen and the ratio of P. nodorum to M. graminicola DNA to climatic and agronomic factors implicated as affecting the prevalence of the two septoria diseases by previous wheat disease surveys or experimental studies. These factors included changes in cultivar grown (7) and harvesting technique, sowing date (17), rainfall in May and June (18), temperature in November and December (19), sunshine in August before sowing (20), the proportion of the cereal growing area sown to wheat (21), and the introduction of fungicide seed treatments and foliar fungicide sprays (8). Agronomic information on the Broadbalk experiment (sowing date, application of seed treatments, and foliar fungicides) was obtained from the Broadbalk ''white book'' record series and national cereal area data from the Department for Environment, Food and Rural Affairs (York, United Kingdom).…”

Spring air temperature accounts for the bimodal temporal distribution of Septoria tritici epidemics in the winter wheat stands of Luxembourg

“…The sexual ascospores represent the primary source of inoculum infecting young winter wheat plants in autumn (Gladders et al, 2001;Hunter et al, 1999). The asexual conidiospores are formed in fruiting bodies (pycnidia) and these spores represent the secondary inoculum for the epidemic spread and vertical transfer to the upper leaves in spring and summer (Gladders et al, 2001;Palmer and Skinner, 2002;Royle et al, 1986). After infection, there is a latent period of approximately 20 days (Henze et al, 2007) before necroses with pycnidia appear on newly infected leaves.…”

“…ex Desm. (teleomorph: Mycosphaerella graminicola (Fuckel) Schroeter) is a pathogen of cereals and the primary cause of Septoria tritici blotch in wheat (Chungu et al, 2001;Gladders et al, 2001;Magboul et al, 1992;Shaw and Royle, 1989). Leaf blotch was reported to be the most damaging disease in the wheat stands of England and Wales (Cook et al, 1991).…”

“…Yield losses caused by S. tritici in humid regions range from 30 to 50% if left uncontrolled (Ziv and Eyal, 1978;Burke and Dunne, 2006;Royle et al, 1986). The sexual ascospores represent the primary source of inoculum infecting young winter wheat plants in autumn (Gladders et al, 2001;Hunter et al, 1999). The asexual conidiospores are formed in fruiting bodies (pycnidia) and these spores represent the secondary inoculum for the epidemic spread and vertical transfer to the upper leaves in spring and summer (Gladders et al, 2001;Palmer and Skinner, 2002;Royle et al, 1986).…”