Analysis of the effects of selected gronomic factors on the dynamics of the take‐ all disease of wheat in field plots

Abstract

Linear models were used to investigate the effects and interactions of treatments for the control of disease in multifactorial experiments on the dynamics of the take‐ al disease of wheat. Analyses were based on repeated measures of disease on second successive winter wheat crops in three successive se sons. The treatments were date of sowing, presence or absence of triadimenol‐containing seed treatment, autumn nitrogen and chloride applications, timing of early spring nitrogen and total spring nitrogen applications. The effects of treatments were investigated on line and quadratic trends of disease increase and on the integral amount of disease over time. Different disease variables were used to express disease relative to the total and diseased plant populations. The effects of treatments on absolute and relative numbers of diseased roots per plant were also analysed. During three se sons when disease was never severe, the effects of the treatments were shown to be variable. Late sowing consistently reduced disease during the early stages of the epidemic (in the winter months). The effect of late sowing in reducing disease, however, persisted through to the end of the growing se son in only one of the 3 years of the study. autumn nitrogen application and Baytan seed treatment (containing triadimenol) also reduced disease in some seasons. The presence of an effect for either was dependent on sowing date and was most evident on the proportion of diseased roots relative to the diseased plant rather than the total plant population.

Effect of nitrogen fertilizer application timing on nitrogen use efficiency and grain yield of winter wheat in Ireland

“…The work also indicated that autumn slurry application is not an effective strategy to supply N to winter wheat crops under Irish growing conditions. earlier application of N may be beneficial, although Werker and Gilligan (1990) found no effect of altering N application timing on take-all dynamics. The increase in RE N of fertilizer N when the first application was delayed until GS 37, compared to making the first N application at tillering, is consistent with previous findings (Recous and Machet, 1999).…”

Factors affecting the temporal progress of stem canker (Rhizoctonia solani ) on potatoes (Solanum tuberosum)

“…The degree of curvature was similarly computed as a quadratic contrast. Details of computation are given in Werker & Gilligan (1990).…”

“…Perhaps the easiest way to achieve this is to simplify the system used for scoring the disease. Werker & Gilligan (1990) argued that conventional estimates of disease severity, in which the number of healthy stems is included, confounds the incidence of disease (i.e. presence or absence) with the multiplication of disease on an infected plant.…”

“…with zero classes omitted (Werker & Gilligan, 1990), and one host variable: total number of stems (N), were used to quantify the temporal progress of stem canker and to ascertain how the growth of the plant was affected after infection by R. solani.…”

“…Agronomic treatments were selected for their ability to produce a contrasting range of environmental conditions with an emphasis on factors expected to affect host growth and/or disease development prior to emergence. Because the effect of agronomic treatments on disease may vary during the course of a growing season, it is important to monitor disease at regular times throughout a growing season as individual or infrequent assessments of disease may fail to detect significant treatment effects (Werker & Gilligan, 1990). In this paper, observations of stem canker were made on six occasions during each of two consecutive growing seasons.…”