Top tips on cultural chafer grub and leatherjacket controls from Colin Mumford

In April 2015, we heard about the loss of imidacloprid, the active ingredient in Merit® Turf. The use up date for existing stocks was 31 October 2016 after the withdrawal from sale and distribution last year on 31 October 2015. Read on to hear Colin Mumford’s top tips on cultural leatherjacket and chafer grub controls.

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Dr Colin Mumford, from the Envu Turf Solutions Team, reminds turf managers and greenkeepers that after 31 merit Turf is no longer registered for use and must be disposed of correctly by a registered contractor because it will be classed as illegal hazardous waste.

These changes mean that there is now no chemical solution available for the control of chafer grubs or leatherjackets in the UK grassland and amenity sectors.

Alternative control methods

“There are a number of alternative control methods, many of which have been used for decades by greenkeepers across the country, however with no chemical control available, due to the EU restrictions on neonicotinoids, I would suggest reviewing practises in order to keep on top of the problem,” says Colin.

Cultural control

The removal of the organic matter, more commonly known as thatch, lying in the upper root zone, takes away a key food source for chafer grubs and leatherjackets. Ensuring nutrition and water levels are not in excess minimises surplus growth and therefore reduces thatch build up.

If thatch is already present, then scarifying the area will physically rake out any thatch lying on the surface. Also applying a top dressing can dilute thatch build-up due to the mineral component. Finally, hollow tining, a process that involves removing small plugs of the turf, can be used to help take away some of the thatch.

Limiting water applications is always recommended, even more so when chafer grub and leather jacket eggs have recently been laid (May-June and August-September). “If the eggs do not receive any water they can desiccate and become unviable, therefore limiting the size of the hatching population. This can only happen in dry weather and when irrigation can be stopped for a number of weeks in a single period.

“An old saying was that if you have a wet September, you know you’ll have leatherjacket problems the following year - an old wives’ tale perhaps, but it really highlights the importance of monitoring environmental factors and understanding the pest,” adds Colin.


Understanding the pest is key to integrated pest management, the natural predators of chafer grubs and leatherjackets are nematodes, these will be an essential control in any greenkeepers toolbox for the foreseeable future.  Heterorhabditis bacteriophora is the species used to control chafer grubs and Steinernema feltiae for leatherjackets, these can be used at the same time without disrupting each other as they only effect the target organism. This method has proven to be effective for several years, if applied at the correct time in the correct temperatures.


Top tips for nematode use

  • Storage – ensure that adequate refrigerated storage is available in order to keep nematodes dormant before application
  • Water – a large volume of water is required to mix with the nematodes before spraying, this will help them travel into the soil, but this also must be the correct temperature
  • Further irrigation is then required to ‘water in’ the nematodes, so that they reach the target hosts
  • In the absence of an irrigation system, use a greater ratio of water to nematodes during application
  • Soil temperature – nematodes are most active in the soil when it’s temperature is above 12°C, ensure that the soil is warm enough or the nematodes will remain dormant
  • Timing – applications should be made after the eggs have hatched

Turf managers and greenkeepers should bear in mind that nematodes are a curative rather than a preventative measure as they cannot survive without their target species as a host.

Colin adds that “pheromone traps are an excellent way of monitoring whether chafer grubs or leatherjackets are present in the area, this will then allow for a targeted nematode application.”

Secondary pest control

“We term chafer grubs and leather jackets as primary pests, but the visible, more devastating damage is done by secondary pests, these tend to be badgers, foxes or birds. The primary pests feed on and damage the grass roots, if the grass is watered, there will be no visible sign of this until secondary pests lift the weakened turf to access and feed on the grubs,” says Colin.

In order to control foxes, fencing can be installed either around the perimeter of a green or the entire golf course to stop them entering the area in the first place.

Envu technical manager and pest control expert, Richard Moseley, suggests that, “in most cases birds are encouraged to populate areas such as golf courses, gardens and parkland, however it’s sometimes necessary to frighten birds away if they are damaging the turf.”

Handheld and programmable, fixed lasers are an increasingly popular bird deterrent in a variety of situations including golf courses, flat rooves and landfill sites. If used correctly, specialist lasers are highly effective, safe and have been seen to change the behaviour of birds.

“The use of specialist lasers for bird control is silent, long range, animal and environmentally friendly. It causes next to no disturbance to humans and only deters birds from target zones, allowing them to continue their residence in surrounding areas,” adds Richard.

Colin Mumford adds that feedback indicates that industry professionals are extremely unhappy about Merit Turf’s removal from the market. He reminds them that “Envu is always looking for solutions to the problem, but in the meantime, an integrated approach to control is more important than ever and lifecycles should be taken into account when considering cultural control methods.”

For further advice on alternative control methods contact the Turf Solutions Team on 00800 1214 9451 or email