In their own right, grubs are often a nuisance because they damage garden plants almost invisibly at a subterranean level. An infestation in the raised bed can be particularly annoying because of the targeted crop planting. But the pests can also be dealt with in the raised bed.
In raised beds, grubs are best dug out by hand
Identify grubs in the raised bed
If you discover curved, whitish larvae when preparing your raised bed for planting in spring, you are usually dealing with harmful grubs. The beetle species, whose larvae feed on the roots of living plants, tend to lay their eggs in suitable places. In other words, where grass, herbs and tender vegetables grow. It is very likely that grubs in raised beds come from
- cockchafers
- June bugs or
- garden beetles
The larvae of all these beetle species look very similar, especially those of May and June beetles. However, with a length of only about one centimeter, garden chafer grubs are significantly smaller than the 5-7 cm long cockchafer and June beetle grubs. However, all have the typical C-shaped, thick-fleshed, yellowish-whitish appearance with three bent pairs of breastbones.
Measures against raised bed grubs
Methods before planting
If the raised bed is not yet planted, it is relatively easy to remove the grubs. After all, you don't have to take care of (not yet infested) plants and you have free access to the soil.
Read out by hand
If you discover the annoying larvae before planting, you can still carry out a cleaning operation relatively well by hand. To do this, read the animals out of the earth as completely as possible.
exchange earth
Another measure that offers BEFORE planting is the complete replacement of the soil. Of course, this is a bit time-consuming and requires a lot of new soil. In return, you will get rid of the grubs completely - provided you are not careless.
With existing planting
If you discover a grub infestation in the raised bed during the cultivation phase, for example through sedentary vegetable plants or during deeper earthwork, combating it is more difficult. After all, now the plants are "in the way". Somewhat more sophisticated methods must be used here.
simulate rain
You can also take advantage of the grub's special habit of crawling to the surface when it's wet. Water the raised bed soil to simulate rain. After a while, the grubs will appear on the surface so you can easily collect them.
use nematodes
While collecting is a very direct and easy way, it most likely won't catch all grubs. Instead or in addition, you can use predatory nematodes. The nematode worms of the parasitic genus Heterorhabditis infest the grubs and cause them to die with secreted bacteria.
All methods that are suitable for the cultivation phase can of course also be used before planting.
A little tip: If you identify grubs in your raised bed, also examine the rest of your garden for any infestation. It is unlikely that the adult beetles only laid their eggs in the raised bed.