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Cockchafer Control

Cockchafers, also known as Maybugs or Doodlebugs can often be seen on May evenings in the garden or flying into lit windows. They are quite large and emit a loud buzzing noise as they fly (hence the name doodlebug), but they are perfectly harmless. The adult beetles are not really a pest but their larvae do a lot of damage to crops and plants.

Ther are currently no insecticidal products licensed to treat cockchafers. Control is biological with the use of nematodes, which are watered into the soil and attack the cockchafer grub.


  • Cockchafers were once very abundant, before the advent of pesticides took them to near extinction in some parts of Europe.
  • Today, their numbers are increasing, due to a recent Europe-wide phasing out of chemical pesticides.
  • No chemical pesticides are currently approved for the treatment of cockchafers, only biological ones, such as fungi or nematodes that kill the grubs in the soil.


  • The cockchafer is a large beetle, 2-3 cms long.
  • The wing cases are rusty brown in colour, the head and thorax black and the legs brown.
  • They are easily distinguishable by their fan-like antennae.
  • The larvae are fat, white grubs that with a brown head and curved shape that live in the soil.
  • The larvae are often called rookworms, because the rook family are very fond of the adult beetles and their grubs


  • Adults appear at the end of April or May and live for about 5 to 7 weeks.
  • The female lays her eggs in soil at a depth of about 10 to 20 cms. She does this several times until she has laid 60-80 eggs.
  • The larvae, also known as chafer grubs or rookworms hatch after 4 to 6 weeks.
  • The grubs develop in the earth for 3 to 4 years, in colder climates even longer and grow to 4-5cm.
  • They pupate in the autumn and develop into an adult cockchafer in 6 weeks.
  • Cockchafers overwinter deep in the soil and make their way to the surface in spring.

Adult cockchafers eat the leaves and flowers of a large range of deciduous trees and shrubs, but do not appear to be serious pests. They are more common in the South. The larvae on the other hand are serious pests of grasses and cereals, as they live in the soil feeding on the roots. They can be serious pests in gardens, nurseries and pastures, causing extensive brown patches to appear. They are also very palatable to corvids and whole lawns can be wrecked as these birds dig them out of the soil.

Leatherjackets, which are the larval stage of the crane fly or daddy-longlegs are a similar pest and will also cause damage to lawns and borders. They can be treated in exactly the same way with biological nematodes.

Poorly maintained lawns are more susceptible to damage, so attention paid to feeding, watering and moss prevention can help avoid damaging infestations

You can buy pathogenic nematodes, usually Heterorhabditis bacteriophora, which attack the larvae by infecting them with a fatal bacterial disease. These microscopic animals can be watered into the lawn when the ground is moist and soil temperature range between 12-20ºC (55-68ºF). This biological control is available by mail order from some biological control suppliers or some garden centres. The turf around the edge of affected areas should be targeted to deal with larvae spreading out from infestation “hot spots". However, by the time areas of infestation become apparent, the soil may be too cold for nematodes to be effective. As a preventive measure, apply nematodes in July to September. Nematodes should be applied as soon as possible after purchase, following the suppliers' instructions. It may be necessary to water the lawn before and after application to ensure the soil is sufficiently moist for nematode activity and survival


What are the habits of the full grown beetles?


Fully grown chafer beetles feed on the leaves of trees and plants but do not do much damage and the adult is not considered to be a pest. They are mostly active at night. It is the grub stage of the lifecycle that does the damage by feeding on the root system of plants.

Will dousing the lawn with the appropriate pesticide kill current and future generations or just the current one?


If you decide to use a pesticide on your lawn, then I believe this should eliminate this years infestation of chafer grubs: Provado Lawn Grub Killer, the active ingredient is: imidacloprid

Should I worry if I have cockchafer grubs in my grass, will they do any long term harm.


Chafer grubs are a pest as they are root feeders and will cause large brown patches on your lawn especially as the ground dries out. They also can do serious damage to flowers and vegetables. Starlings, magpies and crows may also make a mess of your lawn as they dig them up. However they are harmless to humans as are the resultant beetles. If you only have a few I would be tempted to leave them alone. They tend to succumb to dry conditions so if this year\'s summer ever materialises the dry ground conditions will control them. The chemical imidacloprid will kill common chafer grubs but is not effective against the leathery skins of the cockchafer. Also it is highly toxic to other wildlife. If you would like to get rid of them, give the heterorhabditis nematode a try. They are natural aggressive organisms that you water into the ground and kill the grub by getting inside and releasing bacteria that prevent the grub from feeding. We don\'t stock them but they are available online

I put out a light last night with soappy water underneath. This morning I had a had full of the little creatures. When do they put their eggs in the ground.


Adults appear late april early may and the female will start laying her eggs about two weeks later. The grubs will stay in the ground for about four years before they pupate into adults. There are no chemical pesticides approved for use against the cockchafer. Killing the adults will interrupt the cycle or introducing nematodes to the soil to kill the grubs

how to stop grubs in pots?


A soil insecticide that contains imidacloprid should do the trick. Bayer do a range, I believe the product line Merit or Premise is quite easy to get hold of in garden centres

I have cockchafers that get into my pot plants,I have changed the soil but they still return, can you please tell me how to get rid of them


The best route would be the heterorhabditis nematode. This is a natural and aggressive organism that you water into the soil after which they get inside the grub and release bacteria to stop the grub feeding, thereby killing it. They can be bought online from specialist suppliers.

What product can I buy to kill the cockchafer larvae which are destroying my plants?


Heterorhabditis megidis nematodes. Mix them with water and apply with a watering can on a non-sunny day so it doesn't dry out too quickly. The best time is late summer. The tiny creatures will take care of your chafer grubs but without harming anything else.

My grass has nearly been obliterated by these cockchafer grubs and the crows that are digging them up. My grass has been laid for 18 months never had a problem till now. Will my grass reattach and thrive again? What can I use to prevent these grubs?


Grass is very hardy so there is no doubt it will recover but it is also possible you will get a new infestation of grubs next year. Try to get your hands on some heterorhabditis nematodes. They are natural aggressive organisms that you water into the ground and eat the grub from the inside. Just search for them on the internet

What chemical can I use to kill Redheaded Cockchafer Grubs?


You could use a pesticide called Provado Lawn Grub Killer and that will eliminate the grubs for this year. Be warned though that the chemical it contains, imidacloprid, is extremely toxic to other wildlife. You could try the heterorhabditis nematode which is a natural organism you water into the ground. They burrow into the grub and kill it by releasing bacteria that prevent the grub from feeding.

Badger damage caused by digging holes for cochafer grubs or beetles emerging need product to get rid of future infestation if available, legal etc.


The best thing to use against cockchafer grubs are heterorhabditis nematodes which are aggressive organisms you water into the ground and destroy the grub from the inside. They are natural organisms so won't harm the badgers and other wildlife such as a strong chemical would