title: Dose and number of applications that maximize fungicide effective life exemplified byZymoseptoria triticion wheat - a model analysis.
abstract: Two key decisions that need to be taken about a fungicide treatment programme are (i) the number of applications that should be used per crop growing season, and (ii) the dosage that should be used in each application. There are two opposing considerations, with control efficacy improved by a higher number of applications and higher dose, and resistance management improved by a lower number of applications and lower dose. Resistance management aims to prolong the effective life of the fungicide, defined as the time between its introduction onto the market for use on the target pathogen, and the moment when effective control is lost due to a build-up of fungicide resistance. Thus, the question is whether there are optimal combinations of dose rate and number of applications that both provide effective control and lead to a longer effective life. In this paper, it is shown how a range of spray programmes can be compared and optimal programmes selected. This is explored withZymoseptoria triticion wheat and a quinone outside inhibitor (QoI) fungicide. For this pathogen-fungicide combination, a single treatment provided effective control under the simulated disease pressure, but only if the application timing was optimal and the dose was close to the maximum permitted. Programmes with three applications were generally not optimal as they exerted too much selection for resistance. Two-application fungicide programmes balanced effective control with reasonable flexibility of dose and application timing, and low resistance selection, leading to long effective lives of the fungicide.
authors.affiliation: Department of Computational and Systems Biology Rothamsted Research Harpenden AL5 2JQ UK.
authors.forename: F
authors.initials: F
authors.lastname: van den Berg
authors.affiliation: ADAS High Mowthorpe Duggleby Malton YO17 8BP UK.
authors.forename: N D
authors.initials: ND
authors.lastname: Paveley
authors.affiliation: Department of Computational and Systems Biology Rothamsted Research Harpenden AL5 2JQ UK.
authors.forename: F
authors.initials: F
authors.lastname: van den Bosch
keywords: effective life; fungicide resistance; healthy area duration; leaf blotch; selection ratio