June beetle: Recognize, prevent & fight

June beetles are annoying and their larvae can cause massive damage to the roots of plants. We show how to fight the grub.

The June beetle, with which the ribbed curl beetle (Amphimallon solstitiale) is meant, has been occurring more frequently for a number of years. In some areas of Germany the beetle has become a real nuisance. How to recognize the June beetle, how to prevent and control it, you can read in this article.

Recognizing June beetles: appearance of the beetle and its larva

It is precisely the root eaten by the grubs (meaning the larvae) that can cause severe damage to lawns. Due to the damaged roots, the lawn takes care of nests and can later dry out completely. If the dried up turf can be peeled off in the affected areas without any problems, this is another indication of a larval infestation of the June beetle. Now at the latest you should get to the bottom of the matter by looking at the earth under the dead lawn nests. If you find thick, creamy white larvae with the typical crooked posture in the ground, then they may be June beetle grubs. They have six striking pairs of breastbones and a brown head, as can be seen in the picture below. The larvae, which can be up to 3 cm in size, can easily be confused with the blue larvae of the garden beetle and the cockchafer. In principle, however, it is not necessary to differentiate between the larvae, since the larvae of all three scarab beetles are pests and should be controlled if they occur more frequently. The grubs can also damage other plant roots, but the damage is often only visible to lawns.

The brown and airworthy June beetle reaches sizes of 14-18 mm. This makes it much smaller than the cockchafer, which can reach a body length of up to 30 mm. Furthermore, on closer inspection, the June beetle can be recognized by its yellow-brown hair and the three-part antennae on the head. The unpleasant beetles mainly fly to fruit trees and other deciduous trees and cause damage to the leaves there. As a rule, however, the adult beetles are not a problem. Due to their limited lifespan, infected plants can also recover quickly.

Junikäfer: A wanted poster

Only from the summer turn (21. June) the June beetles appear by mid-July at the latest. When dusk sets in, the male beetles fly up and seek out the females that have remained on the ground to mate. The annoying bugs can appear en masse and be really annoying on summer nights. On the other hand, they often don't fly for more than an hour and the ghost is over quickly. The females fertilized after the flight lay their eggs in small groups in the ground. In total, a female lays around 40 eggs in her lifetime. The first grubs hatch from the eggs after three weeks. It takes some time before they become a fully-grown, thick and fleshy larva. The grubs need up to three years to develop. At warmer ground temperatures, as in the south, the grubs only need two years to pupate. In the cooler north, however, larval development takes three years. During this period, the pests feed on plant roots, which we gardeners naturally dislike.

The females prefer sandy and light soils for laying eggs, as the larvae can cope better with dry soil. For this reason, the June beetle tends to avoid damp or even wet locations. Finally, we would like to point out again that the June beetle is in no way dangerous for us humans. They can be really annoying, precisely because they like to use people as landing sites, but they can neither sting nor bite.

Preventing junk bugs

There are good ways to limit the June beetle infestation. Since the beetle itself does not cause long-term problems in most cases, you should focus on the grubs. Because lawns are often used as a breeding ground for the June beetles, they have to be made so unattractive that the female looks for another garden to lay the eggs. In this way, the sensitive lawn roots in particular are protected from the voracious larvae. You can achieve this protection by maintaining your lawn regularly. In plain language this means: regular fertilization and mowing. This creates a dense sward and egg-laying becomes a torture for the June bugs. In addition, the lawn should not be cut too deep, because this also makes it more difficult for the June beetle and other scarab beetles to penetrate the soil and thus to lay eggs.

In particularly badly affected areas (such as Freiburg), the installation of so-called lawn protection fabrics at shallow depths has prevailed. Such a purchase is associated with high costs, but the June beetles can no longer get into the ground to lay eggs. Your lawn remains free of white grubs and molehills are a thing of the past.

Fight June bugs

In addition to the preventive measures, direct control is also possible. However, it doesn't make sense to trap the flying junk bugs. Because this only reduces the number of males and in the end there are still enough males left to mate. Special garden beetle traps are also available in stores. These are expressly unsuitable for catching June bugs. You should therefore focus on the larvae when combating them.

When fighting the white grubs, it should be noted that no pesticides can be used. In general, the use of pesticides in the soil is very problematic, as the microorganisms are very sensitive to even the smallest amounts of pesticides. The use of beneficial insects has therefore proven its worth for combating. In this case, they are predatory nematodes. More precisely, it is bacteria that are secreted by the nematodes and break down the grubs. The grubs, which are pre-digested by the bacteria, then serve as food for the nematodes. The beneficial organism, which is completely harmless to us humans and pets, is called Heterorhabditis bacteriophora or HB nematodes. The beneficial insects are simply used with the irrigation water. For example, if you have our Plantura HB nematodes buy, you will receive the tiny roundworms in powder form and dissolve them in water according to the enclosed instructions. Once the nematode solution has been spread over the area to be treated, the beneficial insects get to work and parasitize the grubs.

Application of HB nematodes as beneficial insects:

• Use against June bugs takes place between July and September
• The floor should be at least 12 ° C warm
• The floor must be kept moist (not wet!) For the duration of the application
• Only apply nematodes in the morning or in the evening, as the beneficial insects are very sensitive to light
• If the infestation is particularly severe, the application may have to be repeated

In our special article you will find everything you need to know and other possible uses for Nematodes as beneficial insects.

Alternatively, the soil can also be processed with a milling machine (processing depth 10 cm). In this way, most of the grubs are rendered harmless and further control of the larvae may no longer be necessary. This control strategy should of course only be used in an absolute emergency. Apart from the destroyed plants on the ground, the soil quality suffers considerably from the milling. The soil structure is destroyed in the long term and only recovers very slowly.

White grubs can wreak havoc on your lawn. It is therefore important to control the larvae early on. In this article you will find our best tips too Control of white grubs in the lawn.