Azanapthalene (AZN) [Group 13] fungicide resistance management strategy

New strategy 2023, M. Christie and R. Beresford

Introduction

The purpose of this guideline is to help maximise the useful life of fungicides in the Fungicide Resistance Action Committee (FRAC) Group 13 for controlling plant diseases in New Zealand by providing relevant information about the nature of pathogen resistance to this group and guidance on practices that may prevent or reduce the development of resistance.

Disclaimer:

The fungicide and bactericide resistance information in the mode of action group table, the mode of action-based strategies and the crop-based strategies is intended to help manage the effects of pesticide resistance on plant disease control by agrochemicals in New Zealand. The New Zealand Committee on Pesticide Resistance (NZCPR) is a subcommittee of the New Zealand Plant Protection Society (NZPPS). The following parties: NZCPR, NZPPS, any people named in the strategies and any organisation the people may be affiliated with, do not guarantee that the resistance information is complete, consistent, accurate or up-to-date, or that resistance will not develop, or that the degree of resistance will decrease, as a result of the resistance information being used, and the parties accept no liability for loss or damage arising from the use of the resistance information contained in these strategies.

Product perspective

AZN fungicides are used internationally for controlling powdery mildew diseases in a range of crops, including cereals, grapes, cucurbits, fruiting vegetables and strawberries. They have only protectant activity and therefore must be used preventatively before infection occurs. In New Zealand, two Group 13 azanapthalene active ingredients are registered for use in New Zealand: 1) quinoxyfen in the aryloxyquinoline chemical group and 2) proquinazid in the quinazolinone chemical group, with current label claims for apples, grapes and cucurbits (Table 1).

Table 1: Mode of Action group 13 products registered for use in New Zealand
Active ingredientProduct nameCrop
Quinoxyfen Proxima®, Quintec™, Vitae™, Vitae™ 250SC Grapes
Squash
Proquinazid Talendo® Apples
Grapes
Marrow, Melons, Pumpkins, Squash, Zucchini

Current status of AZN resistance

AZN fungicides inhibit signal transduction by an unknown single-site mechanism and are considered by the Fungicide Resistance Action Committee (FRAC) to be at medium risk of resistance in target powdery mildew pathogens. Resistance management is therefore required. 

Internationally, resistance to quinoxyfen is known and cross-resistance to proquinazid has been shown in Erysiphe necator (grapevine powdery mildew) but not in Blumeria graminis (powdery mildew of wheat and barley). No practical resistance to Group 13 fungicides has been found in New Zealand to date, however, overseas, isolates with reduced sensitivity have been found to occur naturally.

Resistance management strategy 

Apples and grapes

Cucurbits

Implementation recommendations

Product labels for products containing AZN fungicides should include an appropriate statement about resistance management. This should be under the heading "Resistance Management" and indicate that the product contains a GROUP 13 azanapthalene fungicide that is at risk from resistance development with details of how resistance risk should be managed.

Acknowledgements

This strategy includes information from The Fungicide Resistance Action Committee (FRAC) about mode of action groups, the occurrence of resistance worldwide and resistance management recommendations.