Fighting click beetles and wireworms – Elateridae profile

Short profile about the click beetles

• Around 10,000 species worldwide
• 400 genera
• In Germany over 100 species
• Some glow in the dark
• Beetles 0.9 to 75 mm long, quite flat, hairless or plumed and brown
• It is named after its ability to catapult itself into the air with the help of a jumping apparatus
• A clicking sound can be heard (click beetles)
• The larvae (wireworms) live in the soil.
• They are the real pests.
• They are 10 to 60 mm long, are usually yellowish with a darker head and have three pairs of legs.
• The larvae can be identified by the characteristic shape of the last segment of the abdomen.
• Some of them feed on the roots of crops (seed beetles)
• Agricultural pests
• Feeding marks especially during the months of May, June and July
• Beetles are common

The way of life of the click beetles

In order to be able to fight the beetles, one has to know a lot about their way of life. This is the only way to find them and initiate countermeasures. Wireworms are often found in the soil for several generations. It is not very easy or difficult to get rid of.

• Beetles overwinter in the ground
• In May the females lay around 200 eggs
• Eggs are white, about 1 mm in size
• They are placed in moist soil, a few centimeters deep
• The larvae, the wireworms, hatch in July and August
• They don’t like drought and are very sensitive to it
• Larvae pupate in the ground, 20 to 30 cm deep
• First they feed on dead plant material, then later on living plants
• When the soil gets too dry for them, they invade roots and tubers
• Sometimes they also retreat deeper into the ground, where they wait for the next rain
• It usually takes 3 or 5 years for the beetle to develop

Tip
The cycle of the larvae can be significantly disrupted by tillage. Both the eggs and the young larvae, which are still quite immobile at the beginning, are at great risk of dehydration. By working the soil, they come to the surface and dry out. The active feeding phases of the larvae are between the beginning of April and the middle of May, between the end of June and the middle of July and between the middle of August and the beginning of October. This is the time you can do most of the damage.

Which plants are particularly fond of infestation?

The wireworms are actually not picky. But if you have the choice, you prefer both flowers and vegetables. In the case of flowers, there are more tuberous plants such as dahlias.

• Chicoree
• Strawberries
• Potatoes and beets
• root vegetable
• Tubers
• Kohl
• Most
• Carrots, parsley, broad beans, lettuce
• Saddlery
• asparagus
• tomatoes
• Onions
• Ornamental grasses
• Especially like on damp meadows

How can the infestation be recognized?

The round drill holes can be recognized, especially by the ejection, the small heaps next to the entrance. Roots that have been eaten or eaten away can be found underground. The plants can usually be pulled out of the ground very easily.

Tip
Not only the damage caused by eating is a nuisance, the bacteria and fungi that follow the foot close to the foot are sometimes even worse. These can endanger the entire harvest. Wireworms are harmful throughout the growing season and should be controlled in good time.

Natural enemies of the click beetle and wireworms

Before tackling the problem yourself, you should do something to encourage these natural predators. They have to feel comfortable in the garden, then they relieve the plant lover of a lot of work.

The natural enemies include ants, especially the smaller species, lizards, chickens, hedgehogs, all insect eaters, ground beetles, toads, moles, mole crickets, roller wasps, shrews and many birds, e.g. blackbird, redstart, woodpecker, starling, stork and hoopoe. These animals feel most comfortable in natural gardens.

The control of click beetles and their offspring

Fighting the click beetle or its offspring is not that difficult if you know how to proceed. Much research has been carried out in the field in recent years and the results are impressive. A lot can be achieved here with very simple means.

Mechanical methods

• Dig up regularly – which is usually only possible with unplanted beds. The larvae are exposed and destroyed by natural enemies.
• Liming brings an improvement in acidic soil, because wireworms do not like a calcareous substrate. First loosen the soil, then lime!
• Anyone who knows that wireworms are present can sow or plant wheat between their vegetables. The pests prefer wheat and leave the vegetables alone as far as possible. In addition, the larvae and wheat can be dug up.
• Even carrots and potatoes cannot withstand the pests, which is why they can be used as bait. You cut them in half, mark them so that you can find them again and dig them in, always with the cut surface facing down, in the middle of the vegetable plants. The bait is attacked quickly and can be dug up and destroyed after a few days.
• Drawing trenches and filling them with horse manure attracts the worms. In the spring, the manure is disposed of along with the lured pests inside.
• Tagetes and marigolds are toxic to wireworms. It therefore makes sense to place them everywhere in between. The worms eat at the roots and then die.
• Do not sow crops too closely or prick out generously.
• Plant lettuce as an attractant. After wilting, dig up and destroy immediately with the surrounding soil.
• Place the beds specifically under water. The worms come to the surface and can be collected.

Tip – never mulch the beds. Only use ferns when there is a need to mulch.

Pesticides
At the moment there are no suitable preparations for the home garden. However, since the lists often change with the approved means, it makes perfect sense to inquire about them.

Fight with natural means

The metarhicon fungus kills wireworms. There are several of these mushrooms. At the moment they are still being researched, including their applicability against other pests such as ticks and black weevils. Mushrooms may serve well in the future when it comes to getting rid of pests.

Metarhizit anisopliae is a fungus that is harmless to humans and that occurs naturally and uses insects as host bodies and kills them. It works on around 200 different insects. An aggressive strain that was bred for this very reason is already being used in agriculture after many years of research. It should be much more environmentally friendly than chemical products. However, like all other products, this product will eventually show side effects. One can only hope that they are not serious.

In any case, when the mitospores come into contact with the insect’s body, they germinate and invade it. The fungus develops inside the pest and kills it within a few days. If the humidity is high enough, a white coating develops on the carcass, which turns green as soon as spores are produced.

The difficulty is to find a remedy with the active ingredient. The mushroom was approved in Germany under the product name “BIO 1020”, but was then not marketed. It is marketed in Switzerland. There are, for example, grains of barley that have been infected with the fungus. These have to be planted and the spores will do their job.

Anyone interested in the environment should ask why the active ingredient was not approved in Germany after all. Since there are many remedies that do some work, but are quite helpful, you should try them first, before you enter the cycle of nature in a changing way.

Control through crop rotation

The click beetle population can be influenced by the structure of the crop rotation. But this topic would have to be dealt with separately. Various butterflies such as field beans, French beans and grain peas are well suited as preliminary crops. Some cruciferous vegetables such as cabbage, oil radish, and various types of mustard are also known for their negative effects on wireworms. In addition, however, the soil should always be worked.
The cultivation of various catch crops and undersown crops, on the other hand, does not affect wireworms. See also http://www.oekolandbau.nrw.de/pdf/ Pflanzenbau/Broschuere_Drahtwurm2010.pdf

Frequently asked questions

Are there any other fungi that can be used to control but are easier to obtain?
The use of the mushroom Beauveria bassiana and products based on it have also proven to be effective. But I have found more indications that this fungus is used against the palm weevil in the Mediterranean region. Since Metarhikum anisopliae also helps against the black weevil, this fungus can of course also be useful against wireworms. It is primarily bred in the Soviet Union and China, and it is unlikely to be that easy to obtain either. The product Naturalis L is permissible in commercial cultivation (also for organic cultivation), mainly when used against the fruit fly, which infects cherries, raspberries and now also grapes in large numbers and causes great damage. However, no funds are available for the home garden. But that can change at any time,

How can you detect wireworms on larger areas and, above all, find out how many are there?
Anyone who owns a large piece of land as a private person and wants to grow vegetables, preferably potatoes, has to set up traps. The best time for this is spring, as soon as temperatures rise above 15 ° C for several days for the first time. A paper plate with swollen grains is laid out per hectare at around 20 different places at a depth of 10 to 20 cm. These stay there for 7 days. Then it can be examined in how many traps there are wireworms and how many there are exactly. If you find dozens of worms in each trap, you should refrain from growing sensitive crops.