SPRAY STRATEGIES AND SELECTION FOR FUNGICIDE RESISTANCE: FENHEXAMID RESISTANCE IN BOTRYTIS CINEREA AS A CASE STUDY

Abstract

Fungicide resistance is a limiting factor in sustainable crop production. Despite the wide adoption of general resistance management strategies by growers, the recent rate of resistance development in important fungal pathogens is concerning. In this study, Botrytis cinerea and the high-risk fungicide fenhexamid were used to determine the effects of fungicide dose, tank mixture, and application timing on resistance selection across varied frequencies of resistance via both detached fruit assays and greenhouse trials. The results showed that application of doses lower than the fungicide label dose, mixture with the low-risk fungicide captan, and application post-infection seem to be the most effective management strategies in our experimental settings. In addition, even a small resistant B. cinerea population can lead to a dramatic reduction of disease control efficacy. Our findings were largely consistent with the recent modeling studies which favored the use of the lowest possible fungicide dose for improved resistance management.