Mechanisms by which fungicides increase grain sink capacity and yield of spring barley when visible disease severity is low or absent

•Triazole and strobilurin fungicides increase spring barely yield in absence of disease.•Increase results from an increase in grain number formation.•Effect is not associated with control of asymptomatic pathogen infection.•Effect is not associated with increase in light interception by healthy tissue.•Single application during booting can elicit the response.