Post-harvest recognition of various fungicide treatments for downy mildew of hops using comprehensive pesticide residue monitoring

Abstract

The objective of this study was to evaluate integrated pest management (IPM) practices among hop growers in relation to downy mildew. Forty-eight hop samples, originating from the Saaz hop growing region (Czech Republic) and harvested in 2018 and 2019 seasons, were analyzed using HPLC-HR-MS/MS and AAS methods. Of all the samples analyzed, residues of Ametoctradin, Azoxystrobin, Boscalid, Dimethomorph, Mandipropamid, and Pyraclostrobin, and residues of copper-based fungicides were found at levels ranging from 0.02 to 32 mg/kg and from 7 to 404 mg Cu/kg, respectively. Hierarchical clustering analysis (HCA) was applied to categorize the samples according to the fungicide treatment schemes used to control fungal plant pathogens. The data showed that (1) there was not one universal fungicidal sequence commonly used by all hop growers, and (2) that the sum of pesticide residues varied by more than two orders of magnitude, depending on the fungicide treatment scheme. This study suggests a new approach for evaluating Integrated Pest Management (IMP) practices used in hop-yards on the basis of post-harvest recognition of various fungicidal sequences.