Which are harmful and which are not?

the essentials in brief

• as Grubs are the names of the larvae of the various scarab beetle species.
• Most white grubs live in the ground for years, but they can also be found in raised beds, in flower pots or in compost.
• Not all grubs are pests, some - such as the larvae of the rose beetle or the Rhinoceros beetles - are even very useful for humus production and are therefore welcome guests in the Compost heap.
• Harmful grubs can be combated with various non-toxic methods, but they usually only become a problem when they occur in large numbers.

What are grubs?

White grubs are relatively large, mostly light-colored larvae

The larvae of various species of beetle from the scarab beetle family (lat. Scarabaeidae). The name comes from the old or Middle High German and refers to the appearance of the larvae: It means something like "maggot" or "little worm".

Scarab beetles are a very large family, comprising over 27,000 different species worldwide. Only a few of these are found in our gardens, and many are endangered or threatened with extinction. become very rare. This applies to the cockchafer, for example, whose grubs could cause considerable damage and famine in earlier centuries. In the 1950s to 1960s, the animals were fought radically, so that they are hardly to be found today. In some years, however, they occur on a massive scale and can cause major regional damage.

However, not all scarab beetles and the associated grubs can be classified as pests. On the contrary, because the larvae of the rose beetle and the very rare rhinoceros beetle (which is also under nature protection) are considered beneficial insects.

In the garden and on the balcony you will mainly find these species:

The beetles are crepuscular, which is why you will find them either in the evening or early in the morning.

What do grubs eat?

While the adult beetles usually feed on leaves, flowers or sap, theirs live White grubs in the ground and prefer to eat decomposing plant material and living plant roots. The larvae of the May, June and garden tree beetles like to attack plant roots and can thus damage the vegetation in the garden. The grubs of the rose or rhinoceros beetle, on the other hand, mainly eat dead wood and other dead plant material. Therefore, especially rose chafer grubs are often found in the compost. There they help to convert the plant residues into valuable compost.

Harmful grubs or beneficial insects?

There are grubs in every garden. The pest larvae of the cockchafer, for example, usually do little damage, at least if they only occur sporadically. They only become a problem in the event of a massive occurrence. In addition, it makes sense not to kill all the thick, white maggots at once: You should be able to differentiate between the rose beetle and the rhinoceros beetle from the harmful species. They are very useful and should therefore be kept alive. But you can also let the larvae of cockchafer and co. Live around the now rare animals don't bring them back to the brink of extinction - at least if you only have single grubs find.

Identify white grubs: characteristic differences

You can also use this test to differentiate between harmful and useful grubs:

1. Turn the grub on its back.
2. May or June beetle larvae remain lying around
3. or try to wiggle sideways.
4. June beetle larvae usually crawl lying on their stomachs.
5. Rose beetle larvae stretch all pairs of legs into the air on their backs
6. and move with caterpillar-like movements.

The larvae of the rhinoceros beetle, on the other hand, are easy to distinguish from the other grubs by their sheer size.

Recognizing white grubs: lifestyle and damage

But by which characteristics do you recognize that there is a problem with grubs in the garden? We will now investigate this question in this section.

Way of life and image of damage

It is typical for all types of grubs that they can live in the ground for up to five years before they pupate. The larvae of May beetles and curly beetles do not feed exclusively on plant roots - these varieties also eat plant remains and live in them humus. Only after pupation do the adult beetles leave the earth and can mainly be seen at dusk.

While the quite large beetles are noticeable in the garden, an infestation with white grubs is usually late or late. noticed by accident - for example when digging up a bed. Attention is required when plants threaten to perish for no apparent reason - often they can simply be pulled out of the ground due to a lack of roots. If you dig a little in the ground, you'll find thick, white grubs.

Digression

These plants are particularly at risk

Fight grubs

Plants that are already visibly damaged by the grubs' feeding activity can no longer be saved because the Above-ground parts of the plant are no longer adequately supplied with water and nutrients due to the lack of roots can be. They dry up and can be easily pulled out of the earth. To prevent the infestation from spreading to other plants, you should control the grubs as described in this section.

Collecting

In the past, children would collect cockchafer and their larvae in the summer months - in some Years ago there was a regular plague of cockchafer, so that the animals were radically fought became. Even today, collecting is an effective method of control, albeit a laborious one. The best thing to do is to wait after a heavy downpour, because then the animals come to the surface and can be easily collected. Alternatively, you can vigorously water the infested garden areas with the Garden hose and lure the grubs up. Of course, you can also thoroughly dig up the soil and remove excavated larvae. However, this method is only advisable if the bed is free or should be evacuated anyway.

Biological control with nematodes

The use of nematodes is easier to carry out and just as effective. These are roundworms that you can buy from specialist retailers especially against May or June beetles. The tiny animals become in one Clay granules supplied, which they stir into water and then pour into the bed - if possible in the evening, because nematodes die quickly on contact with UV light. The microscopic roundworms only become active in the earth, penetrate the bodies of the grubs and kill them.

With beneficial insects against grubs

Birds like to eat grubs

It is particularly practical to bring animal helpers into the garden when fighting grubs. The thick larvae as well as the beetles are a popular food for hedgehogs, moles, birds, mice and bats and are eagerly eaten. Make it comfortable for these beneficial insects in the garden, then the pest population will remain small from the outset. These measures help:

• Setting up and attaching quarters: For example, piles of brushwood and stones as hiding places, hedgehog and bird houses, bat boxes
• Feeding stations and drinking troughs: for birds and hedgehogs, e.g. hedgehog feeding in autumn and bird feeding in winter (watering in summer)
• Planting protective and fodder plants: for example dense hedges, native fruit trees (rowan berries, Cornelian cherry, Hawthorn etc.)

If you have chickens, you let them run over fallow beds, lawns and meadows in spring or autumn - the animals peck the tasty grubs out of the ground. But be careful: chickens like to scratch and don't stop at delicious vegetables (such as salad), so the cackling flock does not necessarily move in the freshly planted or freshly planted areas. Leave the sown garden.

Does the use of insecticides against grubs make sense?

Some pesticides that are effective against white grubs and approved for home and hobby gardens are available from specialist retailers. Products made from the seeds of the Indian neem tree are very effective. These contain poisonous ingredients that, like other pests, hinder or even kill beetle larvae in their development. But be careful: just because it is a natural remedy, it is still not safe. Neem oil also has serious effects on the garden ecosystem and also damages beneficial insects and other garden dwellers - for example birds or hedgehogs. Therefore, you should only resort to such remedies when all other methods have failed and you have practically no other choice.

Digression

Which home remedies help against grubs?

Horse manure attracts grubs

An old home remedy for grubs is horse manure. Dig horse manure traps in between April and May Garden soil consisting of buckets filled with fresh manure. The bucket opening should be flush with the surface of the earth. The beetle larvae - at least those that have not yet eaten roots - feel attracted by the smell of manure and crawl inside. Now all you have to do is dig up the buckets and bury the manure and grubs somewhere else. If you repeat this procedure every year, you will soon have no more problems with beetle larvae.

What else can help against grubs? Fight in the garden and on the balcony

Now grubs not only frolic in the garden bed, but also on the compost, in the raised bed, in the flower pot or in the balcony box. What helps or helps against the larvae in such cases? You can find out here whether targeted control is necessary or useful.

Fight grubs in the lawn

If larger brown spots suddenly appear in the lawn, which gradually enlarge, then grubs could be behind them. You can further investigate this suspicion by simply digging up a piece of the affected lawn - you will likely find some beetle larvae there. If not, the dried up grass is most likely due to another cause.

The methods and means already described help against an infestation, you can also cover smaller lawns with an insect protection net during the beetles' flight time, which takes about three weeks. Nematodes of the species Heterorhabditis and Steinernema, which you can spread over large areas from temperatures of twelve degrees Celsius, are also practical for use on lawns.

Fertilization with calcium cyanamide

Who not only the grubs, but also weeds, moss and all sorts of others Lawn problems wants to get rid of it, fertilizes its lawn with calcium cyanamide - this is highly toxic for the beetle larvae and therefore kills them. However, this is only advisable if the pH of the soil is below 6.5. Before using it, you should therefore carry out a pH test, which can be carried out with a simple test stick from the hardware store or pharmacy. Then mix a heaped tablespoon of calcium cyanamide per square meter of lawn with a large shovel of compost and distribute both as evenly as possible.

White grubs in the raised bed

The useful rose chafer larvae should be left in the bed

Raised beds with their abundant filling and the humus-rich soil are a popular playground for grubs. Here, too, it is important to do a test before a possible fight - useful Beetle larvae, such as those of the rose beetle, should be left in the bed, as they ultimately contribute Humus formation. May and June beetle larvae, on the other hand, either collect them out or, in the case of a very severe infestation, fight them by simply replacing the potting soil. Of course, this only works if the raised bed has not yet been planted.

If you only discover the white grubs when the raised bed is already fully planted, only these measures will help:

• Collect, if possible after watering or a rain shower
• Use of nematodes
• Horse manure trap (also works with compost)

Be sure to plant garlic in the raised bed - for example in a mixed culture with strawberries - since May and June beetles and their larvae avoid its strong smell. In spring, it also makes sense to preventively cover the raised bed with an insect protection net. This not only helps against grubs, but also against other common pests and hungry birds that are only too happy to peck the freshly sown seeds.

White grubs in the flower pot

If, on the other hand, there are grubs in the flower pot, only consistent potting and complete replacement of the substrate will help. Regular repotting and protective measures such as covering with an insect protection net also help against re-colonization. Incidentally, beetle eggs and larvae are sometimes found in planting or Potting soil, are thus introduced. A previous disinfection of the substrate in the oven or in the microwave can kill the unwanted accessories (as well as any sciarid mosquito eggs or fungi).

The disinfection takes place

• in the oven for half an hour at 200 degrees Celsius
• in the microwave for ten minutes at the highest level (600 or 800 watts)

Moisten the substrate well beforehand and do not forget to open the window. With both methods, an intense, not necessarily pleasant odor develops.

Effectively prevent grubs

Insect protection nets prevent the females from laying eggs

You can prevent an infestation with harmful grubs by making the garden unattractive to the adult beetles, especially during the main flight season. Do not leave any lights on at dusk or at night, not even solar lights along the Main route - these only attract the beetles, so that the females intensify their eggs in illuminated Lay gardens. Other best practices for prevention include:

• Mosquito nets: Place insect protection nets on beds, dung and compost heaps during the main flight time of the beetles. These prevent the female beetles from laying eggs.
• Ground work: Typical gardening work such as hoeing, raking, weeding and digging disturbs and damages the beetle larvae.
• Root protection grid: Such protected root stocks cannot be reached by grubs and therefore cannot be eaten.

You should also make it difficult for the grubs to get to the feast, for example by surrounding garden beds with lawn edging stones that reach deep into the ground. These represent an insurmountable barrier so that the animals cannot migrate from neighboring plants or beds.

Digression

Which plants help against grubs?

frequently asked Questions

When do grubs hatch?

Most scarab beetles mate between April and May, after which the females lay their eggs. In the months of June and July, white grubs finally hatch in the ground. They stay in the ground for between three and five years before they pupate and develop into finished beetles.

How long does it take to develop from a grub to a cockchafer?

Cockchafer and other beetles are grubs for most of their lives

Cockchafer and other scarab beetles spend most of their lives as grubs - their development from the larval stage to the final stage of beetles takes between three and five years. Adult beetles - called imago -, on the other hand, are only granted a short life span: the male dies after their wedding flight, the females after they lay eggs. The adult phase usually lasts around four to seven weeks.

How long do grubs survive in the ground?

White grubs remain in the ground for between three and five years. Their speed development is primarily dependent on the region and the prevailing climate there dependent: In warmer regions the development from larva to beetle proceeds faster than in colder regions Climates. However, by no means all grubs reach the adult stage: A large part is previously eaten by predators and succumbs to infections (e. B. by fungi), is killed by gardeners or simply does not survive the winter.

How deep are grubs in the ground?

May and June beetle larvae are close to the surface, after all they mainly eat roots. You can usually find them at a depth of between five and 25 centimeters. Only when they pupate do the grubs move deeper: the pupae can now be found up to 60 centimeters deep. They stay here for about a year or two.

Can you eat grubs?

In this country - in contrast to other regions of the world - it is not common to eat beetle larvae and most people are likely to develop quite a disgust at this idea. In fact, grubs are edible, even if we do not recommend consuming them. Depending on what such a grub has eaten, it can be highly poisonous and therefore harmful to health. The larvae do not mind the toxins of many plants, but they take them up in their bodies and pass them on to their predators.