April 2021 FAQ’s

In April 2021 I mainly spent the month talking about two things – How dry it is and how damaging leatherjackets are!

Dry and cold

There is no getting away from the fact that April 2021 has been brutally dry and cold. I pulled some data out on the month just to get my head around how dry it really has been you can find that here……... Whilst its been a record year, on the rainfall front, It’s not actually that unusual. Looking over the last 11 years the dry years have outnumbered the wet ones nearly 3 to 1. The Agronomic odds are very much in favour of dry Aprils. I think we’re all still hoping for April showers but sadly they are not the norm.

The thing that did surprise me though was just how cold the coldest period of April was for a sustained period. That definitely isn’t the normal and whilst we are seeing these colder dryer springs and I’m sure the rainfall will grab the headlines the cold temperatures were the real problem. Particularly when most people were desperately in need of some growth to help recover from the leatherjacket activity they are seeing.

PrimoMaxx II and timings

A couple of people were a little surprised when I put a blog out earlier in the year about the use of PrimoMaxxII and when to start, you can find it here….. where I said I’d delay applications on greens until we saw consistent growth. Spring for me is a period to get some consistency into greens and growth is an important part of that. Through this challenging period of the year I’d take as much growth as nature will give me. On wider large areas however I’m very happy to double down and let nature suppress growth and a PGR assist too, save the labour, fuel and keep out of the way of golfers a little longer.

The benefit of using the 200GDD model at base temp 0C is that it accurately counts the period of suppression during these cold temperatures. If you applied early and are unsure when to reapply, use the greencast GDD calculator to work out 200GDD at base temp 0C and that’s a good time to re-apply. If you’re using 6C as a base temp it will not work well during this period as we have spent most of the month with an average temperature below 6C so it simply doesn’t log the numbers.

GDD why I’ve changed my mind – good read if you’re using a base temp of 6C

Beginners guide to GDD


April now feels like the crunch point for leatherjackets. This feels like the biggest challenge to hit the industry for a while and looking at the data submitted by people back in January I’m increasingly of the opinion that the milder the temperatures are the more likely we are to see damage. blog about that here……...

The above map shows the courses that reported significant loss of turf in that survey and when you look at this compared to the below winter 2020 temperature maps below it seems a correlation worth investigating further.

Metoffice anomaly maps – useful resource that can be found here….

What concerns me about that is knowing how cold it’s been this Spring I suspect the cooler temperatures have held the damage at bay and as we see milder winters (which seem inevitable) it becomes clear how much work needs doing to enable us to sleep easy in the Spring. I’ve put an article together with BIGGA this month on this very subject, so keep an eye open for that one.

Leatherjackets and sheeting

Greenkeepers are a very innovative bunch and it’s great to see so many people reacting to the challenge and adopting old school cultural methods in sheeting greens to control leatherjackets. A couple of words of warning though and things to bear in mind while doing this.

Was it always like this and we just didn’t know?

There is an assumption that old chemistry kept things 100% clean and there didn’t used to be any leatherjackets in our rootzones. I suspect that is not an accurate assumption and when we look back at some of the older advice (STRI put this together in 2017) at that point a threshold of 16 a m2 was deemed acceptable and a level that wouldn’t have impacted the quality of the turf. If we do the maths on that based on a 500m2 green that’s 8000 of them. That was deemed an acceptable level. Now we have increased the level of monitoring and tried to further our understanding of this pest all of a sudden our tolerance to them has become zero.

Clearly this pest can do alot of damage but we’ve lived with them for a long time in our swards and probably didn’t even know. Even with older technologies I suspect we dealing with very similar numbers in many situations and just not aware of it. The danger now we’ve increased our awareness, is that they will get blamed for everything. I’m very happy about this raised awareness and in the long term I’m convinced it will lead to much healthier surfaces than we had previously but we just need to be careful that we don’t overreact.

How much labour needed?

I’m seeing a lot of people undertaking this practice and for many it is essential. One course manager has been good enough to share his labour figures with me and it was frightening. To spray all surfaces it would take him around 17 hours but to date this year he has spent more than 360 man hours adopting the sheeting method. That doesn’t feel sustainable for most venues to me and I think we need to get back to the older philosophy of understanding what is a sensible threshold – if we are going to chase zero tolerance with these then the amount of labour required and disruption to golf are going to be the limiting factors.


April didn’t deliver the Leatherjacket hatchfest I was expecting but I suspect it’s only a few weeks away – as soon as the temperatures pick up I think we’ll see it – make sure you’re logging your sightings on PestTracker.

Read about why it’s important here….

Chafer grub Emergency Authorisation

Good news, the Emergency Authorisation for 2021 has been granted and we’ll be launching that along with lots of technical support over the next month.

Fingers crossed for a warmer and wetter May.

Stay safe.

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