Onion – Downy Mildew

Crop(s):          Onion

Disease(s):     Downy mildew

Resistance Management Strategy for:

Group 4                    Phenylamides (PA);
Group 28 + 23         Carbamates + benzamides;
Group 40                  Carboxylic acid amides (CAA);
Group 49                  Oxysterol binding protein inhibitors (OSBPI); and
Group 49 + 11         OSBPI + quinone outside inhibitors (QoI).

  1. Start disease control early and maintain a regular program using a fungicide from groups other than Group 4, 40 or 49 (or 49+11).
  2. When conditions favour disease development, do not wait for disease to appear, but apply two consecutive sprays of a Group 4, 28+43, 40, 49 (or 49+11) product at the interval recommended on the label. Then resume the program of sprays using products from a different mode of action group to the Group 4, 28+43, 40, 49 or 49+11 products just applied.
  3. Do not apply more than four sprays of a Group 4 or 40 product per season.
  4. Do not apply more than three sprays of a Group 28+43 or 49 (or 49+11) product per crop. Group 49 (or 49+11) containing sprays should not consist of more than 33% of the total number of fungicide sprays per crop.
  5. Apply Group 4, 40 and 49 (including 49+11) fungicides preventatively. Apply solo products of Group 4 and 49 fungicides only in mixtures with a registered fungicide from a different mode of action group, with no known resistance.
  6. Apply Group 4 and 49 (or 49+11) fungicides preventatively and only in mixtures with a registered fungicide from a different mode of action group, with no known resistance.
  7. Continue alternation of fungicides between successive crops. Do not make more than (6) six total applications of a Group 49 (or 49+11) product per year on the same area targeting the same disease.

URL: https://croplife.org.au/resources/programs/resistance-management/onion-downy-mildew-draft-draft/
Content last updated: July 16, 2021

CropLife Australia’s Resistance Management Strategies provide a guide for crop protection product rotation through product groups. The strategies are a useful tool that supports farmers’ adoption of resistance management. All crop protection products must be handled and applied strictly as specified on the product label or APVMA permits.

These Resistance Management Strategies do not replace product labels. They are a guide only and do not endorse particular products, groups of products or cultural methods in terms of their performance. It is important to check with the Australian regulator’s (APVMA) product database for contemporary information on products and active constituents. The database can be sourced through www.apvma.gov.au

The information given in this strategy is provided in good faith and without any liability for loss or damage suffered as a result of its application and use. Advice given in this strategy is valid as at 16 July 2021. All previous versions of this strategy are now invalid.