How to control leatherjackets with nematodes

There are limited options available to control leatherjackets which can make them an incredibly frustrating pest to tackle.

However, with the growing popularity of biologicals to control infestations, one golf course in Hertfordshire conducted a trial to test the efficacy of nematodes

Craig Betts, course manager at Aldwickbury Park Golf Club, conducted a trial to see how effectively nematodes controlled the pest.

 

Why are leatherjackets such an issue?

Leatherjackets, the larvae of the Crane fly, are a troubling turf pest. A single female adult crane fly is able to produce over 300 eggs, which means when an infestation occurs, the population size can cause a significant problem.

Leatherjackets damage the turf grass by eating and damaging the roots of plants, affecting nutrient and water uptake.

They can also encourage secondary damage to the turf, as they can entice predators such as birds and small mammals to their location. These predators will peck or dig at the turf, causing untold losses to the health and vibrancy of the turf surface.

 

What are the control options for leatherjackets?

Chemical control options for turf pests have become incredibly limited in the past few years. This has put significant pressure on the turf industry to find effective alternatives.

Nematodes are one example of a great alternative to chemical controls. This biological option is made up of live organisms (entomopathogenic nematodes), who predate turf pests such as leatherjackets and effectively eradicate the population.

Harmonix® Tri-Nema™ contains a unique blend of three entomopathogenic nematodes which deliver effective control against leatherjackets as well as chafer grubs.

The three species of nematodes each target turf pests in a different way and include:

• The Hunter – a cruiser nematode meaning that it actively seeks out and hunts turf pests
• The Resident – a nematode that sits in the soil and ambushes pests
• The Explorer – a cold tolerant nematode which utilises an intermediate foraging strategy which is between the other two species

Collectively the three species can provide consistent results, as they have the ability to cover a greater amount of the soil profile. They also try to outcompete each other and become the dominant species which makes them much more effective at targeting turf pests.

 

Testing the control of leatherjackets with nematodes

To see how Harmonix® Tri-Nema™ works practically on a working golf course, Craig Betts started the trial in October 2020, a peak time in the season for leatherjackets.

The trial took place on the nine-hole course at Aldwickbury Park, which is split into two sections by the club carpark. This allowed a control and treatment zone to be set up, enabling easy comparison.  

The first five holes had an application of a chemical control and then holes 6 – 9 received an application of Harmonix® Tri-Nema™.

 

The trial results

Following the applications, both courses were visually assessed by Craig.

To measure the presence of leatherjackets, he utilised a tarp test. This is when a 1m² area is covered with tarpaulin overnight encourage leatherjackets to the turf surface.

 

Chemical application area:

On the areas where the chemical controls where applied, there were clear signs of secondary damage from birds pecking at the turf, as well as number of leatherjackets visible around the tarp. While the number of leatherjackets were much less than without a treatment, the population was still not eradicated.

 

Harmonix® Tri-Nema™ application area:

In the area that was treated with nematodes there was little evidence of secondary damage from predators. After the tarp test no leatherjackets were visible on the surface.

Craig explains that for the rest of the season, no damage from leatherjacket activity was noticed and therefore a follow up application was not required.

This is a fantastic result and shows the efficacy of nematode treatments in targeting turf pests.

 

Top tips on how to use nematodes

After the trial, Craig learnt many things about nematode applications and gives advice to others thinking about using the biological control.

 

How to apply nematode treatments

The application method of nematodes is quite different to applying chemicals, but Craig explains that once you know how to apply them it is very easy.

Craig explains they used a vehicle mounted sprayer for applications and made sure to remove all the filters prior to spraying.

He recommends that other greenkeepers should use as much water as possible and also make sure applications are applied in light rain so that the nematodes wash into the soil profile and can get to work as soon as possible.

 

Monitoring for crane flies

Craig notes that whatever control programme greenkeepers use, monitoring of crane flies is incredibly important. This is so you know you’re applying the treatment at the peak time and therefore targeting leatherjackets when they are at their most vulnerable.

 

Cultural controls

Alongside applications of nematodes, Craig has adopted one cultural practice which has helped to reduce leatherjacket numbers.

To keep the turf surface open but not open enough for crane flies to lay their eggs, Craig has reduced aeration depth and started using small pencil tines. He says that cultural controls should be considered just as important as treatments when it comes to controlling leatherjackets.

 

To find out more about leatherjackets, click here.