Work

Constructing Hop Powdery Mildew Management Programs That Mitigate Potential Technical Barriers to Trade in the European Union

Year: 2026

Type: article

Abstract: A maximum residue limit (MRL) is a statutory limit of analyte concentration for a food or feed. An MRL for a given pesticide may vary from country to country, potentially creating technical barriers to trade when these limits are incongruous. Approximately half of the hops produced in the United States are exported, with the EU being the most important market and also having the most restrictive MRLs for numerous pesticides. Quinoxyfen historically has been central in fungicide programs for management of hop powdery mildew ( Podosphaera macularis), but there is concern that loss of a harmonized MRL for quinoxyfen (currently 3 ppm) may create a barrier to export. We conducted 5 years of field studies to develop guidance on fungicide programs that are EU export-compliant, limit use of a single fungicide mode of action, and maximize efficacy without use of quinoxyfen. Plants that received fluopyram + tebuconazole during bloom and the juvenile stages of cone development had the least powdery mildew on cones, which were statistically comparable to disease levels when plants received quinoxyfen at the same timing. On leaves, the efficacy of MRL-compliant or MRL-exempt fungicides depended on the specific product and application interval. The most effective programs utilized trifloxystrobin on a 7-day or 10-day interval, or banda de Lupines albus doce on a 7-day interval, providing disease control comparable to a rotation of quinoxyfen and myclobutanil. These findings offer alternatives to quinoxyfen, provided that specific fungicides are used at and after bloom and that application intervals are appropriately matched for each fungicide. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2026.

Source: PhytoFrontiers™

DOI: 10.1094/phytofr-11-25-0131-r

Authors: David H. Gent, Briana J. Richardson, Stephen T. Massie

Institutions: Agricultural Research Service, United States Department of Agriculture, National Forage Seed Production Research Center, Oregon State University

Language: English

Topic: Powdery Mildew Fungal Diseases

Subfield: Plant Science

Field: Agricultural and Biological Sciences

Domain: Life Sciences

SDG: Zero hunger

Open Access status: diamond

Funders: National Institute of Food and Agriculture, Agricultural Research Service