With their fleshy, light-colored, caterpillar-like appearance, grubs do not look particularly appetizing and, above all, do not look like beneficial insects. In fact, the beetle larvae in the garden can be quite harmful. However, some types are also very useful!
Cockchafer larvae eat the roots of our vegetables
Good and bad grubs
You can't see it quite as black and white as in the fairy tale, but from a gardener's point of view, grubs can be divided into harmful and useful species. Because they feed either only on living or only on dead plant material.
The larvae, which attack living plant parts, more precisely roots, can of course cause corresponding damage. Grasses, young tuberous vegetables, strawberries or lettuce are particularly affected. Withering leaves and fruit and dying patches of grass are the result of the subterranean feeding activity of such grubs. The beetle species whose larvae deprive your garden plants of their livelihood in this way include:
- cockchafer
- June beetle (ribbed tawny beetle)
- garden beetle
Depending on the culinary preferences of their larvae, these beetle species lay their eggs in open garden soil, in flower beds or in flower pots. When the larvae hatch, they go through a long development period of 2 to 4 years. They stay in the ground for that long and eat humus at first, then the tender roots of smaller plants and finally tree roots before they pupate.
Get rid of harmful grubs or don't allow them in the first place
In most cases, however, the damage is relatively limited, since the populations of the beetle species mentioned are no longer as invasive as they were about 70 years ago. To counteract an acute infestation, the grubs should still be dug up and collected or decimated with the help of predatory nematodes. In May and June beetle years it is also advisable to provide beds, flower pots and possibly also lawns with insect protection nets during their flight times to prevent egg laying.
There are also useful grubs
If you spot typically C-shaped, creamy-white grubs on the compost heap, you don't need to do anything. Rather, you should welcome these fellows. Because it is very certain that they are useful grubs of rose or rhinoceros beetles that only feed on dead plant material and produce valuable permanent humus. So let them live in the compost and enjoy their free recycling work.