Tips for Managing Fungicide Resistance in Turf
Fungicide resistance causes a once effective fungicide to no longer provide adequate control of a particular disease. Preventing or delaying resistance should be a primary objective for all turf managers because fungicide resistance will limit their options, increase costs, and ultimately impact their disease management program. The causes behind resistance are thoroughly discussed in the linked article by Dr. Rick Latin, retired turfgrass pathologist from Purdue University. Below are some practical aspects for reducing the chance of developing fungicide resistance.
- Only a few diseases are likely to develop resistance:
- Pathogens that reproduce prolifically, have a short life cycle, and develop under extended periods of favourable conditions.
- Diseases that require numerous fungicide applications throughout the season.
- Diseases that fit these characteristics are Dollar Spot, Anthracnose, Grey Leaf Spot, Pythium and Fusarium.
- These five diseases are the most important to manage wisely to limit the development of resistance in a population.
- Minimize inoculum levels:
- This is a numbers game where the larger the pathogen population (Inoculum), the higher the likelihood of a genetic mutation occurring which might convey resistance.
- Using only curative applications or long intervals between preventative applications allows tremendous build-up of Inoculum and thus more genetic diversity in the pathogen population.
- Make preventative applications for the five primary diseases (listed above) that are most likely to develop resistance.
- Apply fungicides at the appropriate rate and application interval to keep Inoculum populations low.
- Increase the frequency of applications and/or rates during high disease pressure periods where labels indicate rate ranges and different application frequencies.
- Reduce the selection pressure:
- Maximise those cultural practices that help to limit disease pressure – dew management, air movement, regular mowing, rolling, etc.
- Maximise those application techniques that aid or improve fungicidal control – increasing spray volume and decreasing droplet size will improve control with most fungicides (but adhere to instructions on labels).
- Avoid repeated and sequential use of fungicides with the same sites of action (Group number shown on label).
- Alternate between fungicides with different Group numbers, not just different brand names.
- Include multi-site/contact fungicides in tank-mixes as often as practical.
- Additional considerations:
- Though some avoid summer applications of DMI fungicides for fear of growth regulation, Envu’s Dedicate® FORTE Stressgard® Turf Fungicide has excellent summer turf safety and provides critical, broad-spectrum mode of action for rotation of key diseases.
- There are several SDHIs currently available in turf, and dollar spot resistance has already been documented to this fungicide class in the USA. It is critical to not overuse this family of chemistry (Group 7).
- Need more info? See the linked information and contact your Envu regional manager if you need assistance.
Envu's Amplify Turf Consulting Manager, Jyri Kaapro, is a well-known personality within the Australian turf industry, having worked for the past 17 years in Research & Development at Envu. If you have a suggested topic you would like Jyri to discuss please email: jyri.kaapro@envu.com or reach out to any member of our team.
Always read the label before use.
