Next Primo Maxx II app? – Spring edition

When should I next apply my Primo?

The simplest way to understand how to time you're PrimoMaxxII application in the UK is:

  • Cool but just growing: Apply every 4 weeks
  • In between: Apply every 3 weeks
  • Peak summer: Apply every 2 weeks

Stick to that and you won't go far wrong.

You can listen to this blog as a Podcast - just click the link below. It's easy!

Even though it's been cold this spring?

Yep, absolutely. The very purpose of this kind of model (I'll get into the GDD a little later) is to help you adjust your applications so you get consistent levels of growth suppression. The colder it is the longer it lasts, the warmer it is the shorter it lasts.

What if I want more growth suppression - what should I do?

My first response to this is: Why would you want to be suppressing growth during a cold Spring? However if you're happy that's what you are trying to do then simply up rate Primo Rate (remember that 0.4L/Ha is your max label rate on greens).

The rate influences the amount of suppression and the temperature regulates the longevity.

If I increase the rate will it last longer?

Well - technically yes but not really on greens!

In order to gain more longevity from Primo you need to significantly increase the rate (eg. go from 0.2L/Ha to 1.5 L/Ha) which is not the kind of rate we would recommend for greens. Since on greens we're probably only adjusting from 0.2L/Ha to 0.4L/Ha the amount of longevity gained isn't really worth adjusting you programme for.

The GDD bit!

This year I've been encouraging people to use 200 GDD with a base temp of 0C to guide their PrimoMaxxII applications. In the UK we have slipped into a habit of using 6C as a base temperature which doesn't give a good indication of product longevity during the Spring. Check out the blog here......

On the back of that advice let's have a look at how this Spring has panned out with the two different models assuming the first application of the season went on right before that brief warm spell we had in the last week March (seems like a long time ago) and see if my first statement about timings stand true.

Let's look at what we would have done if we'd used 6C as a base temp and 150GDD. Assuming we applied our first PrimoMaxxII app on the 24th March then the 6C / 150 GDD model would imply the next application isn't due yet and is probably due early next week.

one application to get you through this period isn't enough, any suppression seen after the first 4 weeks is likely to be temperature related rather than a Plant Growth Regulator. Looking at this I can see why people haven't committed to the plan - the 6C model isn't a good one for Spring and Summer (it's great for measuring grass growth - poor for measuring product longevity) and using 150GDD at 6C is likely to take you in and out of growth regulation throughout Spring and Autumn.

If we look at 0C base temp / 200 GDD model then you can see the first app went down on the 24th March (same as above), the next app went down on 27th March and the 3rd app is due early next week (approx 24th).

In simple terms:

  • Cool but just growing: Apply every 4 weeks Like this Spring
  • In between: Apply every 3 weeks Hopefully the next few weeks
  • Peak summer: Apply every 2 weeks Hopefully the end of June and the rest of the Summer!!!

Or go to our GDD tool and set up your own thresholds........................

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