I was in a meeting a while back with a few superintendents and one of the questions was on dollar spot and tank mixing. Was it worth it to tank mix fungicides for control? This is a situation that many other superintendents and turf managers face with dollar spot (and other diseases) in Sydney especially under high pressure conditions where 28 days control is unheard of and 21 is a struggle at the best of times.
I know a lot of turf managers in US would be reading this and go through similar issues as well. Weather conditions play a big roll as we know.
Dollar spot in Sydney is a major issue and is pretty much a 12 month disease in many courses with the shoulder seasons more prevalent under a normal summer due to the prolonged leaf wetness and high humidity.. However normal summers are now changing.
Many of you know I am a big advocate of changing your fungicide groups for the past 15 years and I believe there is too much reliance on the DMI chemistry (FRAC code 3). To give you an idea there are 8 separate products with a Group 3 component in them. Just a little confusing. This doesn’t even take into account the generic versions available. So please when choosing a fungicide ask the questions of not just the active but the FRAC group as well.
To help with fungicide choices I have made up a chart for fungicides and their mode of action whether systemic or contact and what FRAC group they are. This can be downloaded clicking here. If you want a laminated copy pleas email me on the address below.
But back to the question of hand of tank mixing. There are 2 options here and I am making these assumptions as is in the theory but practically not relevant in many situations.
- Systemic fungicides last 28 days
- Contact fungicides last 14 days
- We are only dealing with dollar spot here not other diseases so our products mentioned are only dealing with dollar spot control. Other diseases controlled by those products will not be discussed specifically.
The 2 options are
- Tank mix contact and systemic
- Apply contact fungicide followed by systemic fungicide 14 days later
This option is a very strong option and is used regularly not just in turf but apple production as well.
The contact fungicide will work on any resistance strain of dollar spot and will start working straight away (temperature is not an issue) where as the systemic fungicide will take some time as it has to penetrate into the plant which can take time depending on the class of chemistry and the weather and turf conditions at the time of application.
Turf is under stress – the systemic will take time to be absorbed by the plant and if weather is dry and warm the turf is struggling to take up the ai as well.This is why we always advocate to spray in the morning when the turf (cool season) is actively growing. So with this situation the contact fungicide is not effected but weather or turf stress and will start to work work by protecting turf as well as preventing new germination of the disease.
Please note pre mix products are valid here too. Just realise some pre mix products you may not get the residual control you are after. If that pre mix has a lower ai (active ingredient) amount in the dollar spot control product than the stand alone product you can buy.
This option can give up to 48 days control (6 weeks). The contact fungicide will give you up to 14 days and the systemic will give you up to 28 days. Realise that if applying a systemic with resistance issues effectiveness will either be reduced or have no effect at all so you are relying on the contact to knock over the resistance strain. Note same weather issues can impact here as well.
What would I do?
Well I would do both. Option 1 during high pressure times and when you need to target multiple diseases. As well I would use this option when you have a full blown attack of dollar spot.
Option 2 use at lower pressure times and in a more prevention situation may not eliminate the resistant strain of dollar spot if you have a full blown attack.However I would always mix my groups around and limit FRAC group 3.
There are also many cultural practices which have been proven to reduce dollar spot.I urge everyone do do these as well including:
- Remove dew
- Reduce leaf wetness
- Maintain balanced NPK
- Increase light and air movement- if you cant get rid of the trees can you at least trim some branches back?
Thanks for the idea guys I hope this helps in making the best decision for your situation. As always please don’t hesitate to contact me further via phone or email firstname.lastname@example.org
Our new Emerald Fungicide will be available soon and fully registered for dollar spot and other diseases.