Have you found grubs in your compost heap? Congratulations! Because the grub species that make themselves comfortable there are of the useful variety. So you don't have to worry, you can count yourself lucky.
Why are grubs useful in compost?
Grubs in compost, such as the larvae of rhinoceros and rose beetles, are useful because they decompose dead plant material and produce valuable permanent humus. They therefore promote long-term, nutrient-rich fertilization for plants.
Differentiating grub species
The relatively similar-looking larvae of scarab beetles, zoologically known as Scarabaeuoidea, are called grubs. The best known or most common representatives of this superfamily in our latitudes are:
- Cockchafer
- June beetle
- rose beetle
- Garden leaf beetle
- Rhino Beetle
Typical of grubs is their thick, fleshy caterpillar appearance with more or less long legs in the head area. Depending on the species, they can grow up to 10 centimeters long. Grubs live for a long time, namely at least 2 years in their larval stage, before they pupate and transform into beetles.
Grubs are sometimes generally classified as pests. Some of them are anything but that: they are actually extremely useful and should therefore be welcomed by every hobby gardener. Being able to distinguish between the species is crucial to whether you can benefit from them.
Useful grubs
The useful species are in particular the grubs of the rhinoceros beetle and the rose beetle. Why? Because they don't feed on the roots of living plants like the other species we have. They conveniently prefer dead plant material, especially wood. That's why you only find them in compost heaps. When digesting eaten, rotting tree and shrub clippings, these grubs produce humic substances, which, as a humus component that only breaks down very slowly, lead to the formation of permanent humus. Such permanent humus is very valuable for gradual, nutrient-rich long-term fertilization of your plants.
How can rhinoceros beetles and rose beetles be identified?
Aside from identifying themselves simply by their presence in the compost, rhinoceros beetle and rose beetle grubs are also immediately recognizable by their appearance.
The rhinoceros beetle larvae, for example, are particularly large: they can reach up to 10 centimeters, which is why they are very easily visible in the compost heap. In contrast to the other grub species, they lack the so-called row of thorns in the silvery-gray area at the back. Rose beetle larvae are significantly smaller, only about 3 centimeters long, but very thick-fleshed. They become a little thinner towards the abdomen and only have very short legs at the front. The way they move around on their backs is also characteristic.
