June bugs: detection, treatment & prevention

June bugs: detection, treatment & prevention

June bugs are annoying and their larvae can cause massive damage to the roots of plants. Find out how to treat these pests effectively here.

The June beetle, also referred to as the summer chafer (Amphimallon solstitiale), is closely related to the cockchafer (or May beetle). June beetles have been increasing in their numbers in the recent years. In some areas of Europe, the larvae of this beetle cause immense damage to the lawn each summer. In the following, you can learn how to recognise, prevent and treat June beetles and their grubs.

What does the June beetle and its larvae look like?

The grubs (the larvae of the beetle) feed on the roots of grasses which can wreak havoc on lawns. Due to the damaged roots, the lawn can dry out completely. To find evidence of the grubs’ presence, the dried turf can be removed in the affected areas. If the lawn removes easy, it further hints at grub infestation. In order to find direct proof, though, look through the soil directly underneath the damaged area. If you find thick white larvae in the soil with the typical curved body, they are likely the young grubs of June beetles. They have six striking sternum pairs and a brown head as shown in the picture below. The up to 3 cm large larvae can be easily confused with the grubs of the garden chafer and the cockchafer. In principle, however, this is not a problem since the larvae of all three chafer beetles are pests and should be controlled if their population increases. What is more, the grubs can also damage roots of other plants, but the most striking damage usually happens to lawns.

The brown June beetle reaches the size of 14 – 18 mm. This makes it considerably smaller than the cockchafer, which can reach a length of up to 30 mm. In addition, the June beetle can be recognised by its yellow-brown hair and the tripartite antennae on the head. The beetles fly mainly close to fruit and other deciduous trees and cause damage to the leaves. As a rule, however, adult beetles are not a problem. Due to their limited lifespan, infested plants can also recover quickly.

June beetles: a profile

June beetles can usually be found from late June to mid-July.. When dusk falls, male beetles fly up and look for the females remaining on the ground to mate. The annoying beetles can occur in large numbers which can be really irritating during summer nights. However, this does not last long because they usually fly intensively for only around an hour or so. The fertilised females lay their eggs in small groups in the ground. In total, female beetles lay about 40 eggs in the course of their lives. The first grubs hatch from the eggs after three weeks. But, it takes some time until they develop into the full-grown, thick and white larvae. In fact, grubs can take up to three years to grow fully. If the temperatures are warmer, grubs need only two years to pupate. In the cooler northern climates, on the other hand, larva development takes three years. During this period, these pests feed on plant roots and can cause the plant life to die, which makes garden owners crazy.

Female June beetles usually lay their eggs in light and sandy soils, because the larvae prefer these drier types of soils. Therefore, humid and wet locations are avoided by the June beetle.

Before we delve into the prevention and treatment of June beetle grubs, we would like to point out that these beetles are in no way dangerous for humans. They can be really annoying, especially because they like to use people as landing places, but they can neither sting nor bite. So unless your lawn or other plants have been severely damaged, there is really no need to get rid of June beetles.

Preventing June beetles

There are several ways to prevent a June beetle infestation. The adult beetles do not cause any long-term harm in the gardens, so the prevention should focus on the grubs of the beetles. The young beetles breed on lawns, therefore, if the right measures are taken, it is possible to make the lawn undesirable as a breeding ground for the beetles. By making your lawn unappealing to the beetles, the females will not lay their eggs on your property, and the lawn roots will remain protected from the voracious larvae. How is this achieved? The answer is simple: maintain your lawn. Mow and fertilise your lawn regularly. By doing this, the lawn will grow densely, which hinders the female beetles from depositing eggs. In addition, the lawn should be kept longer. Shorter lawns make it easier for the beetles to reach the ground, penetrate the soil and lay their eggs.

In particularly severely affected areas, gardeners started installing the lawn protection fabrics in the soil. Although this is of course costly, it completely prevents the June beetles from getting into the soil. In this way, lawns remain grub-free and, additionally, molehills become a thing of the past.

Getting rid of June beetles

In addition to preventive measures, direct control is also possible. However, it makes no sense to use traps in a case of grub infestation. This only reduces the number of male beetles and there will still be enough males left for mating. There are also special garden chafer beetle traps available in stores and you might be tempted to try those out. Yet these are also not recommended and are, as a matter of fact, not suitable for catching June beetles whatsoever. To treat an infestation effectively, it is vital to focus on the control of the larvae.

beetle larvae
The larvae of June beetle (and other similar species of beetles) are usually harmless; treatment is only necessary in extreme cases [Shutterstock.com/ Dirk Wegman]

We urge you to not use any pesticides when treating grubs. Generally speaking, the use of pesticides in the soil is very problematic, as the microorganisms react very sensitively to even the smallest amounts of harsh chemicals contained in pesticides. An effective yet nature-friendly method of control is the use of beneficial organisms. To get rid of June beetle grubs, predatory nematodes have helped thousands of desperate gardeners before. What makes this method work are the bacteria, that are secreted by the nematodes, which parasitize on the grubs and kill them. This way, the grubs are pre-digested by the bacteria so that the nematodes can feed on them. The beneficial organism is called Heterorhabditis bacteriophora (HM nematodes) and is completely harmless to humans and pets. It is very important that exactly this species is used for control, as it also combats the cockchafer and garden chafer grubs.

Using nematodes to treat June beetle grubs:

  • The soil must be at least 12 °C warm
  • Keep the ground moist (not wet!) for the duration of use
  • Only apply nematodes in the morning or evening, as they are very sensitive to light
  • If the larvae of the June beetle are already very well developed, the treatment with the nematodes must be repeated several times

Alternatively, the soil can be milled (working depth 10 cm) with a milling machine. This eliminates the grubs and further control of the larvae may not be necessary. This control strategy should of course only be used in an absolute emergency. Apart from the destroyed plants on the soil, the soil quality suffers considerably because of the milling. The soil structure is damaged in the long term and recovers very slowly.

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