As of: March 27, 2024, 12:24 p.m
By: Ines Alms
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Root-eating grubs can cause major problems in raised beds.
But not all of them are harmful.
How to distinguish the larvae and remove them correctly.
Before planting the raised bed, you should inspect it for beetle larvae.
Sometimes you notice the animals when you gently turn the earth: the slightly curved, plump white grubs of May or June beetles are up to seven centimeters long.
The larvae of the garden chafer beetle are only about one centimeter in size, but they are still easy to detect and no less harmful.
If you let the grubs in the bed, the pests eat organic material such as roots of herbs, vegetable plants and flowers.
But before you jump into the fight, it is important to distinguish between beneficial and harmful grubs.
Distinguish between harmful and beneficial grubs
You should remove grubs in raised beds.
But you can't just kill them because some are protected.
© CHROMORANGE/Imago
The larvae from the superfamily of scarab beetles are called grubs.
When working on the raised bed in spring, the animals can usually be discovered while digging and can easily be picked up.
If you want to be on the safe side, replace the soil completely.
If you suspect that the animals are feasting on the plants in summer, you can lure them out with a trick: water the bed vigorously and wait.
After a while, with a bit of luck, the animals crawl out into the daylight.
Once discovered, not all grubs should be treated the same.
The rose beetle larvae are protected by the Federal Species Protection Ordinance and may not be killed.
The approximately three centimeter large rose beetle larvae can be recognized by the fact that they move on their backs - with their legs in the air.
Since the beneficial insects provide valuable services in the compost and decompose woody components, they should be relocated there.
If you don't have compost, you can release the grubs on the ground outside the garden in a park or forest.
The huge, eight to ten centimeter large larvae of the rhinoceros beetle also do no harm.
The grubs, which are also protected, are very rarely found in raised beds or elsewhere and are a stroke of luck - because this indicates a well-maintained, natural garden.
They are more likely to show up in the compost and become
treated in the same way as the rose beetle larvae.
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Collecting is the most effective measure against grubs
However, if it is the larvae of May, June or garden beetles, you can either collect them or, depending on the type and size, fight them naturally with nematodes.
This has proven particularly useful for garden leaf beetles.
These nematodes are available online or in garden stores.
They are distributed over the bed with the irrigation water and then fight the grubs.
You can avoid killing the animals by releasing them elsewhere.
Chemical control of beetle larvae is usually unsuccessful.
Prevent grub infestation: The beetles don't like garlic
Natural enemies such as martens or hedgehogs are rare in raised beds - only birds eat the grubs.
One more reason to take preventive measures.
The above-mentioned beetles lay eggs in May and June.
In order to prevent or disturb the animals, you should regularly loosen the soil in the bed at this time and remove weeds.
Plants such as delphiniums, geraniums and garlic also act as a deterrent to beetles in raised beds.
Anyone who adds compost to the raised bed should check it carefully for grubs in advance.