Engerlings are the larvae of certain beetle species. These include cockchafers and June beetles, which are among the best-known scarab beetles. In the larval stage they reach a length of up to six centimeters and are very thick. Their bodies are light, greyish, brownish or yellowish. The head and legs are darker. These can be brown, orange, or even black in color.
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Where can the pests be found?
Engraved grubs live in the ground. Here they dig tunnels and initially feed on rich humus. The older and thus bigger they get, the more their livelihood shifts. So they first eat tender roots of grasses and herbs. Shortly before the transformation into an adult beetle, tree roots are almost exclusively on the menu.
How can the larvae be recognized?
Because grubs live in the soil as larvae for up to four years and can still be found in the substrate for a few months after pupating into beetles, they can cause considerable damage to small and large plants. However, this is usually only noticed when the plants die and can no longer be saved due to the missing roots.
Accidental discovery of the grubs is only possible when digging up. The adult beetles, on the other hand, are more noticeable in the garden.
Prevent the beetles and larvae
The best and most effective protection against grubs is to prevent an infestation.
Two measures are available for this. Firstly, turning off the lights at night. Because the beetles in question are attracted to the light sources in the dark and stimulated to lay eggs in their environment.
If the lighting cannot be prevented, for example because the lanterns are public or the garden is near the city and is therefore never completely dark, there is a second possibility.
This is the laying out of insect protection nets. Spread over beds, these should primarily cover bare soil and protect the compost heap. Because this is where the beetles will primarily come to lay their eggs.
This is not necessary all year round. Only when the beetles fly from May to June. And only if there are numerous specimens in the area.
alternative prevention
If you don’t want to do without the evening lighting or want to wrap beds in nets, you have other natural protection options. This includes:
- Deep lawn curbs
- root protection mesh
- Close-meshed wire inserts
- The regular scarifying of the lawn
- Thorough garden maintenance
Deeply dug lawn edging stones, close-meshed root protection grids and wire inserts represent boundaries that grubs cannot penetrate. Although this does not completely prevent an infestation, it at least limits it.
In large gardens in particular, the introduction of such obstacles represents a great deal of effort. However, this should be invested in at least for larger trees.
Scarifying the lawn regularly loosens the soil, making it less attractive to beetle larvae. The same applies to thorough and basic garden maintenance. To do this, weeds should be pulled out and all dead plant parts should be destroyed. Raking leaves and manually loosening the soil also help.
Remove the pests
Once the grubs have spread, they should be removed. For this it is necessary to dig up as much of the garden as possible and to collect the larvae. At the same time, the substrate is loosened and the amount of roots is reduced. Both ensure that the beetles and grubs do not find a suitable basis and avoid the garden.
For these reasons, it is advisable to frequently subject the floor to such treatment. Where this is not possible, the scarifier will help.
Welcome beneficials
For birds, hedgehogs, moles, martens and mice, grubs are a juicy delicacy. And for these, it is well worth digging in the ground. Especially after heavy rains, when the ground is soft, the grubs dig up and are then easy to find. The beneficial insects mentioned indicate this by numerous holes in lawns and beds.
Instead of simply plugging the holes and scaring away hedgehogs and the like, they should be given free rein. Even if that means having to put up with uneven surfaces first. Because in the long term, pecking birds and digging martens save you having to dig up and replace expensive, large plants.
On the other hand, if you keep the useful animals away with repellent sounds and the like, you only increase the maintenance effort in the garden.
Nesting sites and wild hedges attract birds and hedgehogs. As well as accessible drinking troughs and natural corners in the garden where the animals can stay undisturbed.
The most environmentally and animal friendly measure
May beetles and June beetles – and therefore also their larvae – are found more frequently in the vicinity of parks and forests. An infestation can therefore hardly be completely avoided, but it can be controlled. And with very little effort.
For this purpose, a small area in the garden must simply be allowed to overgrow. Ideally, this is right next to or around the compost. To ensure that this corner continues to be particularly attractive to the beetles, it can be equipped with a light. A solar-powered, ground-level lantern is optimal. The rest of the garden, on the other hand, should remain as dark as possible.
Metal sheets stuck deep into the ground, lawn edges or buried, close-meshed gratings safely limit the area reserved for grubs. This keeps the larvae in “their” corner and away from the rest of the garden.
Targeted use of nematodes
Threadworms, also called nematodes, are underestimated helpers in the fight against grubs. They are inexpensive, natural and unbeatably easy to use.
They only have to be supplied with water, usually with clay granules, and then applied to the desired area. From that point on, they do the work completely independently. The nematodes infest the grubs and silently kill them below the surface. In addition, they do no harm and are completely harmless to other animals and humans.
defensive plant species
Plants can also be used if the beneficial animals simply don’t want to appear. Larkspur and geranium have proven to be particularly useful. Because these are not scorned by the grubs, but have a poisonous effect on them.
Therefore, it is favorable to place them in large numbers in the garden.
Garlic is not toxic but has a deterrent effect and is therefore preventative. This benefits from the fact that it is inconspicuous before and after flowering. As a result, it can be generously distributed in the garden without any problems and without being visually out of the ordinary and, when cut short, hardly stands out even on the lawn.
Safe and natural traps for grubs
Anyone who notices an infestation with grubs or fears a large number of beetles can use traps. These are easy to make yourself and require very little effort. But they are very effective.
- Ordinary buckets of water or large planters are required for the grub traps.
- These should be filled with compost or horse manure. There should be a small distance between the content and the upper edge. About a hand’s breadth is enough.
- The buckets filled in this way must be buried at a depth of about 40 to 60 cm. This is initially associated with quite a lot of work – especially if there are several traps – but becomes easier after the initial lifting.
- After insertion, earth is heaped up. The locations should be marked so that the traps can be easily found again later. Stone circles that follow the outline of the bucket are ideal.
- Spring, between April and May, is the ideal time to deploy the traps. The following year, you should also remove the buckets again in the spring, empty them and fill them fresh. In mild years, emptying in the fall is a better choice.
The purpose of these grub traps is to attract the beetle larvae with the nutrient-rich content. During the first year, the larvae cannot feed on roots, so they remain in the bucket in large numbers. In this way, they can easily be excavated. Annual digging can thus be avoided.
Natural and chemical agents
If the measures mentioned so far are of little or no help, for example in the case of a massive infestation, insecticides can be used.
In any case, preference should be given to natural, organic means. These do not damage the soil or plants and do not pose a health threat.
Chemical products should really only be used when all other means and measures have failed and there is a severe infestation of several hundred grubs.
kill grubs?
A severe infestation with grubs that requires action is rare and is usually limited to short phases every three to four years.
Only then and only if there are hundreds of larvae in a small area should they be destroyed. On the other hand, if only a few grubs are found, it is better to move them. For example in the forest, in a tightly closed composter or in a wild meadow. Because no matter how annoying the beetles and larvae may be in your own garden, they definitely serve a purpose in nature. And they are rarely found.
Beetle larvae as known harriers
The usefulness of grubs, even if it is not obvious at first glance, should not be underestimated.
The larvae ensure that the compost decomposes more quickly and becomes usable soil. The grubs of the rose beetle and rhinoceros beetle in particular feed exclusively on dead organic material and are therefore important cleaners and recyclers in the environment. And in the garden.
Because of their fondness for dandelion and other herbaceous plants, they can also fight weeds from the roots. Even when they pounce on grass and tree roots, they provide loosening and aerating passages along the way.
For these reasons, it is not necessary or sensible to remove every grub from the garden. Appropriate countermeasures are only necessary when the number gets out of hand.
Conclusion
Engraved grubs have a bad reputation, which is not justified in every case. In fact, they can be useful. They spread rapidly in the garden, but appropriate means and measures must be used. And with these you can do without aggressive chemical products in almost all cases.
