Anyone who complains about dead patches of lawn and finds crooked, whitish larvae in their beds or in flower pots is probably dealing with grubs. Certain types of these beetle larvae are classified as pests and are therefore worth fighting. There are various methods for this.
Digging up the grubs is laborious but effective
Interesting facts about grubs
Larvae of beetles from the superfamily Scarabaeoidea, which has a large number of species and species, are called grubs. However, only a handful are relevant to local garden culture. These include above all:
- cockchafer
- June beetle (ribbed curlew beetle)
- garden beetle
- rose chafer
- rhino beetle
The larvae of these beetle species all have a typical appearance that is usually difficult to distinguish from one another. Characteristic is the C-shaped curved form, the clear segmentation, the light, yellowish to cream-white color and the 3 bent pairs of sternums.
Useful and harmful grubs
Who to welcome
Not all grubs are harmful to garden crops, some are quite beneficial too. In order to avoid unnecessary control and not to spurn free help, it is good to be able to identify the useful species. The following are particularly useful:
- Rose chafer grubs
- Rhinoceros Beetle grubs
They feed exclusively on dead plant material and can therefore produce valuable permanent humus on the compost where they prefer to live.
On the one hand, they can be identified simply by their habitation on the compost. Rhinoceros beetle grubs are also conspicuously large at 7-10 centimetres, and funnily enough, rose chafer grubs move backwards.
who does harm
In particular, the following are harmful:
- Cockchafer grubs and
- June bug grubs.
They feast on the roots of living plants, especially grasses and tender vegetables and berries. The damage is reflected accordingly in dead, easily detachable lawn islands and bedding plants that take care of them. Garden beetle larvae also feed on living roots, but with a length of only about one centimeter they are significantly smaller than the 5-7 cm long cockchafer and June beetle grubs and therefore cause rather negligible damage.
countermeasures
In general, you should use gentle methods when fighting grubs. Because they are best for the biological balance of your garden and the environment. The ecological, near-natural options can be divided into the following categories:
1. Mechanical removal
2. Strategic, targeted combat
3. Deterrent and defensive measures
1.Mechanical removal
Dig up and collect
If you notice lawn and bedding damage that indicates a grub infestation, you can first take the most direct route: dig up the ground on the spot and go hunting for grubs. Depending on the strength of the soil and the spread of the infestation, however, shrinkage is inevitable. Catching all grubs is pretty unlikely.
squirt
In the case of grubs in flower tubs, you can also arm yourself with a garden hose or a low-pressure cleaner and spray out the root ball of individual plants.
2. Strategic combat
Curl upwards through wetness
You can proceed somewhat more indirectly by luring the grubs out with intensive watering. Like earthworms, the beetle larvae are driven to the surface of the earth when it rains. So if you water a bed heavily or put potted plants in a soak, the pests will make their way to the surface where you can collect them.
use nematodes
A fairly reliable method is the use of predatory nematodes. Such parasitic threadworms colonize the grubs and release bacteria into their bloodstream, which kill them. Suitable are predatory nematodes of the predatory genus Heterorhabditis, which can be purchased in garden shops or on the Internet and can be applied via the irrigation water.
grub trap
An effective and gentle, but also patience-requiring method is a grub trap. It is easy to set up and gathers the pests in one place where they can then be removed in one go. Fill a bucket with horse manure to just below the brim and bury it in the infested area in the garden soil. It should remain there for a year, until the grubs have crawled into the tempting dung and can simply be taken out of the ground together with the bucket.
Deadly Plants
Some plants are toxic to grubs - and yet they don't stop at their roots when eating. So they unknowingly kill themselves. These plants include geraniums and delphiniums.
3. Deterrent and defensive measures
Deterrent Plants
Certain plants have a deterrent effect on the adult beetles and prevent them from laying eggs. This includes garlic. If you put garlic plants in beds and balcony tubs, you can prevent grub colonization.
insect protection nets
Putting up insect protection nets while the beetles are in flight makes a lot of sense so that you don't get into trouble with the larvae in the first place. In order to be able to initiate the measure in good time, it is of course necessary to follow the May and June beetle years and to prepare the nets from May onwards in the corresponding years.
insecticides
Insecticides should always be the last resort. After all, they not only kill the unwanted pests in an unsightly way, but also beneficial insects and plants. Products available in specialist shops include products such as the harmful Kwizda Agritox Engerling-Frei, Bayer’s “Against Engerling in Lawns” or calcium cyanamide granules.