Factors affecting development of Septoria tritici in winter wheat and its effect on yield

Abstract

Severe infection with Septoria tritici occurred in four of five experiments designed to create a series of different disease epidemics. These experiments successfully identified periods suitable for infection. They also indicated the effect of sprays, timed before and after these periods, on disease development and yield. Analysis of disease progress and weather records suggested that critical conditions for initial development of S. tritici occurred during early May at four sites. Heavy rain giving at least 10 mm on 1 day or a total of 10 mm or more on 2 or 3 successive days occurred at all four sites prior to the appearance of symptoms on a particular leaf layer, though less heavy rain may suffice to splash inoculum onto upper leaves in shorter, immature canopies where stem elongation is incomplete. At the fifth site, infection occurred later in May and disease failed to develop to a significant degree. At all sites, the length of the incubation period on any of the top three leaves was found to be between 396 and 496 degree days. Control of winter epidemics of S. tritici had little effect on yield, whereas spray sequences commencing later than growth stage (GS) 31 but immediately prior to the critical periods provided the best disease control and yield benefit. Regression models incorporating, as independent variables, area under the S. tritici disease progress curve for any of the top three leaves from their emergence (GS 32‐37) satisfactorily explained yield loss at the four sites where disease was severe. Consideration of leaf 2 or leaf 3 alone accounted for more than 82% of the variance at each site and a yield loss from infection of leaf 2 related to thermal time is suggested as 0.00265% per C per day from the appearance of symptoms.

Influence of crop growth and structure on the risk of epidemics by Mycosphaerella graminicola (Septoria tritici) in winter wheat

“…It can cause substantial yield loss if it becomes severe on the flag, second and third leaves (Shaw & Royle, 1989;Thomas et al, 1989). In common practice, control strategies rely on two to three applications of fungicide, for which timing is guided by growth stage rather than by any identification of disease risk.…”

A test method based on microscopic assessments to determine curative and protectant fungicide properties against Septoria tritici

“…A range of decision models has been developed in the past to optimize fungicide input for the control of this pathogen. A few of these models are based, amongst others, on infection-related decision criteria with respect to the long latent period and the limited curative activity of current fungicides (Thomas et al, 1989;Royle, 1990;Schöfl et al, 1994). Some systems include an element to select the most efficient compound in relation to particular requirements (Volk & Frahm, 1991;Habermeyer & Hoffmann, 1994).…”

The effect of leaf rust (Puccinia hordei) on yield response in barley (Hordeum vulgare L.) crops with different yield potentials

“…Similarly, measurement of the effect of yield potential on response to disease required an adequate range of crops with different yield potentials. In studies with a similar demand for a large number of treatment levels, non-replicated designs have been useful (Shane & Teng, 1987;Shaw & Royle, 1987;Thomas et al, 1989), and this approach was adopted in the present study. Check plots repeated several times through the experimental area were used to assess the amount of variation within each crop.…”