White grubs in the raised bed: what to do | Where are you from?

Above all, raised beds in the garden should be a visual eye-catcher with many appealing plants, spices or vegetables. But the unpopular larvae of beetles, which mainly feed on the roots, can also quickly nest here. In the worst case, the plants die off. But what helps against an infestation of grubs in the raised bed and where do the larvae actually come from? The following article explains which measures can help.

Appropriate measures

Appropriate measures to successfully drive the grubs and adult beetles out of the garden include combating and prevention. Insects and larvae can be fought in many natural ways, and prevention is also possible without the use of chemicals. These include:

  • be the first to spot bugs
  • collecting the larvae from soil
  • take good care of the garden
  • this includes floor care
  • attract predators
  • Cover raised beds
  • use threadworms

recognize grubs

Engerlings are larvae of various beetles. These all come from the scarab beetle family (Scarabaeoidea). These include the most well-known species here, the rose beetle (Cetoniinae), rhinoceros beetle, May beetle (Melolontha) and June beetle (Amphimallon solstitiale). The grubs can grow up to six centimeters long and are fleshy and thick. They have a powerful mouthpart on their distinctive head. Some species live up to four years in the ground before they develop into beetles. Furthermore, the fat larvae have the following characteristics:

  • six legs in front of the body
  • help dig
  • abdomen is thickened
  • some species white
  • others brown to orange
  • feed on plant material
  • prefer to eat the roots
  • very dangerous for the plants
Note: Only the larvae of the garden beetle (Phyllopertha horticola) and the May and June beetle are considered pests for the plants. The other beetle larvae tend to feed on dead plant material, prefer to live in compost and are therefore also good for the garden.

detect infestation

An infestation with grubs in raised beds is usually not recognized by hobby gardeners until late. Because the grubs stay mainly underground and do not come to the surface. Only by regularly checking the soil can an infestation be detected at such an early stage. Otherwise, possible larvae in the raised bed can be recognized as follows:

  • adult beetles on the plants
  • mostly late evening or early morning
  • they lay their eggs in the ground
  • Beetles in May and June indicate more larvae
  • then there could be more larvae in the ground
  • or plants suddenly wither
  • Roots were eaten
Tip: So that the plants are not damaged in the first place, you should regularly dig up and water the raised beds and garden beds, then the thick larvae will quickly come to the surface. Since the larvae live in the ground for up to four years, you should carry out this measure regularly throughout the year.

causes of infestation

Specific causes for an infestation cannot be named. As a rule, there are different types of grubs in the ground in every garden, including in raised beds or in compost. These are hardly noticed, since there are usually only a few specimens, which do not massively damage the plants. One of the main causes of an infestation is a poorly maintained garden, because the grubs feel very comfortable in crumbly, hard and dry soil. A well-kept garden is not usually plagued by a large infestation of grubs, since the larvae are constantly disturbed by gardening. Nevertheless, there are always years in which the May and June beetles fly in heaps and then lay more eggs in the raised bed. There are the following reasons for this:

  • Neighboring garden relatively neglected
  • there are many grubs in the ground here
  • become beetles after three to four years
  • these then fly more frequently in spring
  • swarm out into the surrounding area

Fight

If the larvae were found in the ground, then they are easy to fight. First of all, they can simply be removed from the ground with gloves on and then disposed of in a bag in the residual waste, well sealed. The earth can be dug up for this. If this is not possible due to plants standing close together, the soil can also be well watered, then the larvae will come up on their own. Another way to combat it is to use nematodes. The way to do this is as follows:

  • use immediately if an infestation is suspected
  • are commercially sold as a powder
  • mix with the irrigation water according to the manufacturer’s instructions
  • Nematodes are roundworms
  • penetrate the larvae
  • fight them like this
  • Nematodes are harmless to roots and plants
Note: As soon as all beetle larvae have been successfully attacked by the nematodes, the nematodes also die off quickly. Therefore, if there is a new infestation next year, you must also put new nematodes into the soil.

Prevent

Against grubs in the raised bed can be well prevented. The beetles are lured into the garden by light in the dark and then lay their eggs here. Raised beds are also often illuminated in different colors. This should be avoided in May and June, when the beetles are in their active phase. There are also other preventive measures that can protect against egg laying in raised beds:

  • cover with a close-meshed net in May and June
  • remove weeds
  • Maintain soil well and always loosen it
  • also always water well
  • Larvae prefer darkness
  • as well as dry, compacted soil
Idea: It can also be helpful if you pour the soil used through a sieve before creating a new raised bed. Especially if you can mix garden soil with compost, a few beetle larvae will always get into the bed. Only the soil falls through the sieve and the thick larvae remain and can be disposed of immediately.

Create a natural garden

Not only the raised bed, but also the lawn or other vegetable and flower beds can be protected from grubs if a natural garden is created from the start. If natural predators of the grubs and the adult beetles are attracted and they are offered an attractive living environment, there will be less infestation, not only by the voracious larvae but also by other pests. Natural enemies of grubs include native birds, hedgehogs and shrews, as well as moles. For the latter, however, raised beds are not so interesting. A near-natural garden can be created as follows:

  • offer many shelters
  • layered pile of branches in a corner
  • or around the raised beds
  • natural stone walls with many cracks
  • Wall the raised bed with stones
  • Distribute bird nest boxes
  • also long, dense hedge serves as a nesting place

unpopular plants

There are plants that grubs like to plant in the garden, but which grubs generally avoid. Therefore, these can find their way into the beds between herbs and lettuce plants and thus naturally prevent infestation. These plants include the following:

Particularly endangered plants

Engraved grubs do not feed on all plants. However, some are a favorite food of the harmful beetle larvae. Anyone who has planted the following plants in the garden or in the raised bed should pay particular attention to the soil all around in order to quickly identify any infestation:

  • strawberries
  • Salat
  • potatoes
  • beets
  • and all young plants

Kira Bellingham

I'm a homes writer and editor with more than 20 years' experience in publishing. I have worked across many titles, including Ideal Home and, of course, Homes & Gardens. My day job is as Chief Group Sub Editor across the homes and interiors titles in the group. This has given me broad experience in interiors advice on just about every subject. I'm obsessed with interiors and delighted to be part of the Homes & Gardens team.

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