Cockchafer / Close linge

Melolontha-Arten

Changed on: 23.05.2019
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Maikäfer
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Cockchafer

Cockchafers, also known as May bugs, have been known to man since ancient times. While they were worshipped as symbols of spring and fertility in antiquity, their damage to arable crops gradually came to the fore with the intensification of agriculture. There are records of the species of cockchafers being taken to court in Medieval times, when they were ordered to leave the fields. School children were urged to collect May bugs in the 19th century and, in the 20th century, newly emerging agricultural chemicals were used to control cockchafers at such levels that a German song even featured the line "... es gibt keine Maikäfer mehr..." ("…there are no cockchafers anymore…"). However, the number of May bugs has increased over recent years in local areas.

Maikäfer
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Cockchafer

Cockchafers, also known as May bugs, have been known to man since ancient times. While they were worshipped as symbols of spring and fertility in antiquity, their damage to arable crops gradually came to the fore with the intensification of agriculture. There are records of the species of cockchafers being taken to court in Medieval times, when they were ordered to leave the fields. School children were urged to collect May bugs in the 19th century and, in the 20th century, newly emerging agricultural chemicals were used to control cockchafers at such levels that a German song even featured the line "... es gibt keine Maikäfer mehr..." ("…there are no cockchafers anymore…"). However, the number of May bugs has increased over recent years in local areas.

Cockchafer Flight Reporting

Cockchafer Flight Reporting 2016

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Maikaeferzyklen 2017
Maikaeferzyklen 2017

A mass flight of cockchafers must be expected in individual regions in Austria this year (see image on the right). The swarming at the edge of forests or prominent individual trees during the evening is quite conspicuous. This is where the beetles carry out their maturation feeding and mate.

The first large-scale survey on the flight of the cockchafer started about 100 years ago in Austria. At that time, it was design to help predict the beetles’ mass flight, so countermeasures could be put in place in time. Nowadays, the focus of interest has also shifted to its connection with changing climate conditions. Based on the regular development cycle of the cockchafer, predictions where to expect a mass flight Austrian are quite accurate.

The May bugs take about three to four years to develop from an egg into a fully grown beetle, depending on the average temperature. However, the beetles may hatch a year earlier or later in some regions, subsequent to particularly warm or cold years. The animals will keep to this new periodical flight year in the future until the climate changes again. This way, the cockchafer is a good indicator of changes in our climate.

We would like to ask your help in surveying cockchafer flights: you can help us to record the size of the flight for each region by filling out the online form below - the actual date of your observation is not that important. This will enable us to refine the existing cockchafer flight map and document any changes to it. We have prepared several cartoons on May bugs to download onto your computer as a little thank you.

Download cartoons on the life of the grubs and the cockchafer beetle

Contact

Dr. Andreas Kahrer
Email: andreas.kahrerno@Spam@agesno.Spam.at

Reporting Cockchafer Sightings

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Pest

Pest

Cockchafers are members of the family of the scarab beetle (Scarabaeidae), which also include well-known insects such as the rose beetle, dung beetle and rhinoceros beetle. The German name of this family -- Blatthornkäfer -- is derived from the last antennae segments that carry “leaves” or lamellae and can fan out. The beetles grow up to 30 mm in length and appear in a variety of colours: while the majority have a dark head, dark pronotum and chestnut elytra, there are also very dark, completely reddish-brown and lightly coloured specimens, which were given different names by German children (Rauchfangkehrer/chimney sweep, Kaiser/emperor and Müller/miller). There are three different species of cockchafers in Central Europe: the common cockchafer (M. melolontha), the forest cockchafer (M. hippocastani) and the sporadically found, large cockchafer (Melolontha pectoralis), the names of which do not say much about their way of life. All three species look very similar and are also linked, so that they will be treated here, together. One difference is that forest cockchafers have a range that includes  Scandinavia and Siberia, while the common cockchafer is predominantly found in Central Europe.

Mass Flight

The most typical trait seen in cockchafers is their periodical, mass flight. During this time, they can strip bare forest trees, grapevines, fruit and ornamental trees. It appears that in doing so, many cockchafers from one area gather at the edge of the forest at particularly prominent trees to mate – it almost seems to be some sort of “wedding market” for May bugs. The females return to the places they have spent their lives as larvae after mating to deposit their eggs. To do this, they have to dig up to 25 cm deep into the ground – not an easy task.

Oviposition and Hatching of Larvae

The depth reached depends strongly on the ground structure. Once in the ground, they deposit about 30 cream-coloured eggs of about 3 mm. It was found that the female beetles return repeatedly to their swarm trees following the deposition of their eggs to mate again and lay another batch of eggs. The typically shaped larvae hatch after about one month: the U-shaped, forward-bent abdomen is a standard characteristic, in addition to the head capsule and the segmented legs – such beetle larvae are referred to as “white grubs” or “chafer grubs” and sometimes as “rook worms”.

The young grubs first feed of fine fibre roots -- once they grow in size, they turn to the stronger roots of their hosts. During its life phase, the grub sheds its skins several ties, letting us differentiate between three larvae stages because of the grubs’ different sizes. The damage caused depends also on the age of the larvae, in addition to other factors, and are at the most important in the year after their flight. The grubs stay at various depths in the ground dependent on the time of the year: while they live in relatively shallow ground up to 20 cm in depth during the vegetation period, they spend the cold time of the year at depths of up to 60 cm to avoid low temperatures. The old grubs, which have reached a size of 4 cm by then, begin to build a small cave at a depth of approximately 40 cm in late summer before they fly, where they pupate. The finished beetle emerges three weeks later, but remains in the ground to overwinter and works its way to the surface once the ground temperatures have increased in the following spring, closing the cycle.

Development Time

The entire development time lasts for several years and depends strongly on the ground temperature. Development takes about four years in cooler regions, such as in Northern Germany and in many Alpine valleys, while it is only three years in  other areas. This results in mass flights every three or four years, depending on the region. These periods of mass flight vary from region to region. Thus, it is possible to develop a “cockchafer map” by marking regions with corresponding flights in different colours. This was already started by Zweigelt in Austria and continued by Faber and Cate, who recorded the annual flight of May bugs with the help of primary schools across Austria. The current distribution of flight areas is not fixed, but can change subject to climate conditions and ground temperatures. This has occurred repeatedly in the past and, thus, illustrates the historic development of climate change. It is said, for instance, that in a particular part of Switzerland a part of the cockchafer population of a region developed slower following a very cold year and that the mass flight year has moved back one year ever since.

Spread

Regions in which mass flight has to be expected based on the long-term cycles of cockchafers are marked in colour on geographical maps, such as the following. Red dots indicate mass flights that have been observed physically. Mass flight years that came earlier in 2009 in the districts of Kufstein (Tyrol), Deutschlandsberg (Styria) and Feldkirch (Vorarlberg) and late mass flight years in the area around Korneuburg, Stockerau and Tulln are noteworthy, for instance. The analysis of these irregularities could provide information on whether the climate change observed by meteorologists already affects animals.

Reporting Cockchafer Sightings

You are very welcome to share your own observations in relation to May bug flights with us. Click here for our online report form, in which you can see all current flight areas and  download cartoons on the life of the grubs and the cockchafer beetle. 

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Cockchafer grub
Maikäfer-Engerling

White grubs are the typical larvae form for the entire scarab beetle family and  their stag beetle relatives and they develop not only into cockchafers. Other commonly found white grubs are the larvae of the European June beetle (Amphimallon solstitialis), which is a pest in lawns and the grubs of the rose beetle, which live in compost heaps, but do not cause any damage. The particularly large larvae of stag beetles and rhinoceros beetles are found in rotting wood. The larvae of the two latter species are not pests and are protected animals.

Symptoms

Symptoms

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Feeding damage at the root
Fraßschaden an Wurzel

Adult cockchafers feed on the foliage of trees and shrubs to various degrees – even until the plant has been stripped bare. The larvae, on the other hand, feed on the roots of their host in the ground. This results in the affected plants not developing properly or even to the withering and wilting of the entire shoot.

Hosts

Adult cockchafers feed off various deciduous trees and shrubs, such as oak, maple, beech, stone fruit, walnut, larch, grapevine and hazelnut. The larvae feed off the roots of various fruit trees, forest trees, grapevine, clover varieties, bird’s foot trefoil, dandelion, and other meadow herbs and grasses.

Prevalence

Cockchafers are only found in specific areas in Austria. They are completely absent in many Alpine valleys and other high-altitude areas.

 

 

Control

Control

  • Collecting the beetles manually and using them as animal feed 
  • Overturning the ground and tillage destroys part of the grub population. This method is only effective as long the grubs have not moved to deeper ground in preparation for overwintering. 
  • Covering the ground of fields with sensitive crops with nets designed to protect against beetles, to avoid that hatched beetles can get to their swarming locations or that females returning from there deposit their eggs in the soil.  
  • Work Melocont Pilzgerste® into the soil (using a special machine) to infect grubs with the entomopathogenic fungus Beauveria bronginiartii. This method is ideally suited for wetter regions, such as Alpine valleys. The agent should be applied repeatedly, beginning in the year before sowing.  
  • Treating the cockchafer’s swarm locations with the insecticide NeemAzal TS (active substance azadirachtin). This plant-based insecticide inhibits the maturing of the eggs and the grub’s skin-shedding, resulting in a long-term decrease in grubs. 
  • Local treatment with the insecticide Agritox (active substance chloropyriphos) before cultivating sensitive crops and working it into the soil (see Register of authorised plant protection products in Austria).
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