Cockchafers or ‘Maybugs’

Posted by TopVeg - May 30th, 2007

Cockchafer or ‘Maybug’ (Melolontha melolontha)

Class: Insecta
Order: Coleoptera

Chafer Bug larvae can cause devastating damage to young vegetable plants. Chafer Grub larvae are white grubs with a brown head, and distinct pairs of legs at the front end.

The Chafer Grub are 2cm beetles which hatch into flying adults in mid-May. The adult beetle is a night-flier and often comes crashing into lighted windows on warm evenings in early summer, making a buzzing sound. Chafer Grub adults lay eggs in June which turn into more Chafer Grubs in July to eat roots until October. Then Chafer Grubs dig deeper into the soil to over winter until May before Chafer Grub surface to fly, mate and lay eggs. Chafer grubs may feed below ground for 3-4 years before changing into adult beetles.

Adult chafers eat the leaves and flowers of many plants, but rarely cause any serious damage in the UK.

The fat, white grubs (reaching 40-45 mm long when full grown) live in the soil and feed on plant roots, especially lawns, and are occasional pests in vegetable gardens.

The grubs can be found immediately below the surface, usually lying in a characteristic comma-like position. Injury to the roots causes tender tap-rooted plants like lettuce, to wilt suddenly, show stunted growth and to shed leaves. Plants growing in rows are usually attacked in succession as the grubs move along from one plant to the next.

Control chafer grubs by:

  • removing and killing the grubs by hand when they are found
  • good cultivations which expose the grub
  • rolling, if appropriate, squashes them
  • good weed control reduces their food store
  • biological pesticides which include microscopic beneficial nematodes (Heterorhabditis megidis - eel worms) which are watered into the garden with a watering can when soil temperatures are above 10°C. They enter the Chafer Grub and poison it so that it will die within a few days

Posted in pests&disease

9 Comments »

  1. Thanks for this - I’ve often wondered whether maybugs are friend or foe to the gardener, and now I know!

    Joanna
    joannasfood.blogspot.com

    Comment by Joanna - May 30, 2007 8:53 am

  2. Thankyou,This site helped me with my homework.

    I didn’t have a clue what maybugs were but now I also know like Joanna. =]

    LauraHarris…x

    Comment by LauraHarris. - February 21, 2008 7:45 pm

  3. Hi Laura

    Glad we have helped. Thanks for letting us know!

    TopVeg

    Comment by TopVeg - February 21, 2008 8:21 pm

  4. The pictures look more like leatherjackets to me - aren’t chafer grubs white with brown heads?

    Comment by bimwatkins - March 31, 2008 7:45 am

  5. Hi Bim

    Cockchafers have legs and leather jackets do not have visible legs

    Comment by TopVeg - May 3, 2008 10:59 am

  6. Do the larvae attack asparagus? This spring about half my asparagus plants have failed and there are quite a few holes in the soil just the right size to have had the adults emerge from them round about. And I have encountered several adults while out squashing slugs after dark

    Comment by Nicky Huckle - May 22, 2008 10:15 am

  7. Hi Nicky

    What do the adults look like? Have you seen any caterpillars on the foilage. Is the foilage being eaten, or are they dying from the root?

    Asparagus beetle are the most common pest in the UK.

    Asparagus Beetle emerge from the soil in late spring (May and June) and lay black eggs on the asparagus spears and foliage. The creamy greyish-black larvae have yellow spots & are up to 10mm long when fully grown, after which they go into the soil to pupate.They can be picked off individually in most cases .

    But your symptoms sound like Cutworms - which is unusual. The cutworms feed on roots or lower stems and usually are hidden in the soil. Several kinds of fat, soft-bodied, basically gray, black, or brown caterpillars (40 to 50 mm long when fully grown) feed on asparagus roots. Cutworms have three pairs of legs and five pairs of prolegs . Cutworms occasionally feed above ground on spears and ferns when young, but older larvae burrow in soil during the day and sever plant stems at night. They curl up when disturbed.

    What bad luck to loose your asparagus

    TopVeg

    Comment by TopVeg - May 22, 2008 8:28 pm

  8. Thanks for the info, I would have replied before, but had some computer probs. I was a bit premature: more of the asparagus has now emerged. I now suspect slugs as the main culprits for the no-shows, but I am going to wait a while more before I start digging up the roots to check for pests in case they are just being slow.
    Luckily, I haven’t had asparagus beetles yet (touch wood). I’ve had them in a previous garden and recognise the little blighters. The adults I was seeing were definitely cockchafers, and they are still emerging. Now I am not blaming them for my asparagus disappearances I can appreciate them more!

    Comment by Nicky Huckle - June 5, 2008 9:18 am

  9. Hi Nicky

    Thanks for the update - all interesting stuff. Interesting to see the cockchafers emerging!

    Please keep us informed - it will be good to know who is the culprit!

    TopVeg

    Comment by TopVeg - June 5, 2008 10:07 am

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