If a container plant takes care, this can be an indication of a grub infestation. White grubs eat the roots of living plants and not only in the open air. If you discover an infestation, the following control measures are advisable:
- Manual collection
- Wash out
- Float up through the wet
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The most obvious and direct method is manual collection. To do this, loosen the root ball from the bucket, carefully shake off the soil and read the larvae as thoroughly as possible. Because of their yellowish-cream-white color and their size of about 5-7 centimeters, they can also be easily recognized in the dark earth.
The problem with the method is that it is a bit tedious. On the other hand, you will hardly discover all the grubs. In addition, it is no good for plants with dense roots that cannot be penetrated by the fingers.
In the case of plants with dense roots, you can try to flush out the pests with a strong jet of water. Of course, the roots have to be robust enough not to be damaged. But even with this method, some grubs can go through the net or get out of sight with the water flow, so that they are up to mischief a few meters again.
Float up through the wet
Like earthworms, grubs are driven to the surface of the earth when it rains. You can take advantage of this habit. Put the root ball of your container plant in an immersion bath and wait for the animals to show up on the surface. You can then collect them there. But even this method does not claim to be completely removed.
A fairly effective and biological variant is control by predatory nematodes. Certain roundworms of the predatory genus Heterorhabditis use larvae of pests such as May, June and garden leaf beetles as well as black weevils as hosts and kill them in the process. You can purchase suitable nematodes in garden shops or on the Internet. The animals enclosed in clay granulate can simply be brought out with the irrigation water.
Grubs like solid ground. This is why it is important to keep the soil loose and weed-free, as in the open garden soil, with potted plants. Never leave plants in the pot so long that the root ball is completely firm and compacted. That's not good for the plant anyway.
Insect net when flying beetles
To keep May, June and garden tree beetles from laying their eggs in your flower pots, it is advisable to put insect nets over the tubs during their respective flight times. This is not particularly time-consuming and only necessary when the adult beetles are flying - and this only happens every few years, especially with May and June beetles, and only lasts for a few weeks in May and June.