June beetles - detect, prevent and fight

the essentials in brief

• June beetles are best combated with nematodes or fungi - but only in the larval stage
• Infestation in the lawn can be prevented by mowing and scarifying
• June beetle larvae eat plant roots so that they bend and eventually die

Fight June bugs

Fighting adult beetles is often not effective as the grubs develop in the soil. To stop the beetles from spreading, you need to take targeted action against the grubs.

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The larvae need a humidity of 100 percent. They cannot survive on the surface of the soil as they dry up immediately. When you see the first signs of pest infestation, you should loosen and aerate the lawn thoroughly. With a grinder you can completely destroy the larvae population. However, this will destroy the entire soil structure, which is why other control methods are more useful.

Nematodes

An effective remedy are special roundworms that are used against junk beetles. The microscopic creatures are only 0.6 millimeters long and occur naturally in the soil. Of the nematodes, the species Heterorhabditis bacteriophora is one of the natural enemies of the June beetle.

Fighting with nematodes only makes sense in the first larval stage, as the grubs are no longer susceptible to the roundworms after their moult. The roundworms penetrate the living larvae, feed on the cell tissue and multiply in the organism. The grub dies within two days and the nematodes leave the host to infect more larvae. It takes up to six weeks for this control method to achieve maximum success.

Tips

Nematodes should be brought out between August and September. The earlier you start fighting, the better the roundworms can multiply.

application

Specialized powders with live nematodes are available in specialist shops, which are mixed with water and applied to the affected areas. Always mix the entire contents of the bag with water, as the nematodes are not evenly distributed in the powder. Stir the solution thoroughly before filling so that the roundworms do not settle on the bottom.

Pour the required amount into a watering can and pour the solution on the affected areas. If the soil is very dry, it should be watered beforehand. The nematodes require moist conditions and dry out quickly. To prevent organisms from sticking to the blades of grass, you should then water the area.

Good to know:

• Nematodes need a soil temperature of over twelve degrees Celsius
• A drop in temperature during the night does no harm
• great sensitivity to light
• only apply in the morning or in the evening
• Roundworms multiply in two to three weeks
• Keep the soil evenly moist during this time

Parasitic fungi against June beetles

The beetle larvae can be controlled in a biological way with special fungi that live parasitically. Fungi of the genus Metarhizium are used, the species Metarhizium anisopliae being used most frequently as a control agent. When it comes into contact with the grubs, its spores settle on its outer skin. These germinate and pierce the tissue with the hyphae.

The fungus develops inside the larva, so that it dies after a few days. Spring and autumn are given as favorable treatment periods, whereby the temperatures should be warm. Then the grubs are in search of food in the upper soil layers.

Application:

• Mix fungal spores with sterilized barley grains
• Sprinkle the mixture on the ground
• work in well
• Water the lawn generously

Beauveria brongniartii

This parasitic fungus has a way of life similar to Metarhizium anisopliae. Both mushrooms specialize in a few hosts. The use of Beauveria brongniartii remains ineffective against the June beetle. However, this shows an effect in the control of cockchafer.

Pyrethrum

The Caucasian insect flower (Tanacetum coccineum) develops a secondary plant substance that is intended as a defense and has been extracted by humans for many centuries. The active ingredient pyrethrum has a deadly effect on insects, as it spreads in the nervous system and damages the stimulus pathways. The contact poison only works if the beetles are sprayed directly. They stagger, fall from the leaves to the ground and can die. Many manufacturers of insecticides use the substance in their products, which are used to kill pests.

Tips

The spray is no exception to beneficial insects. Pyrethrum is deadly to all insects and should therefore not be used in the garden.

What can be done against June bugs in the apartment?

During their twilight and night flights, June bugs orient themselves to light sources, because these allow the silhouettes of trees and bushes to stand out against the horizon. You can also get lost in apartments if the windows are wide open and light shines inside. Try to catch the animals with a screw top jar and put them outside again. There is no natural means of driving the beetles away.

Build a trap yourself

Scented traps containing a cocktail of pheromones are often used to capture garden leaf beetles. This serves as an attractant and attracts male beetles looking for a partner. The effect of such traps on June beetles is controversial. While some garden owners report successes, attempts to attract other gardens are unsuccessful. If you want to build a trap yourself, you should take advantage of the beetle's way of life. Use artificial light sources as attractants.

How to build a junk bug trap:

• cut a 1.5 liter plastic bottle in half
• Insert the upper part upside down into the lower end
• Hang up vertically at tree or bush height
• place a light source behind it

Tips

You can paint the bottle parts green except for the bottom to simulate foliage. Also enlarge the entrance opening with a cut-off funnel so that the beetles do not fall to the ground so easily.

Prevent June bugs

June beetles feel particularly comfortable in the lawn when it has open spaces and a warm, dry microclimate. To make the areas for oviposition unattractive, you have to worsen the living conditions for the beetle. So that the females do not lay their eggs in the ground, the sward must be as dense as possible. This is possible through regular maintenance. Start mowing for the first time in the spring when the lawn has grown about eight centimeters high.

Lawn care during the year:

• scarify in spring
• then fertilize
• mow weekly
• do not cut too deep

Lay lawn protection

In warm regions, so-called lawn protection fabrics are used so that the uncontrolled spread can be contained. These mats are laid out at a depth of ten centimeters. This is followed by a layer of soil with grass seeds or turf. The material is weatherproof and does not rot. The prices can vary and are around three euros per square meter.

Mode of action

In spring, old larvae cannot reach the plant roots from the deeper soil layers and young larvae cannot retreat to deeper layers of the earth for the winter, so that they freeze to death. The mats also prevent moles from digging up the earth.

Spread out the foil

You can prevent the female beetles from laying their eggs in the meadow. To do this, you must lay foil or garden fleece on the lawn during the flight time so that the June bugs cannot land on the substrate. This measure is only useful in small gardens and must be repeated every evening for several weeks. To avoid damaging the lawn, the film should not be left on the surface all day.

What are June bugs?

Behind the june beetle (English: june beetle or summer chafer) hides the species Amphimallon solstitiale, which is also known as the ribbed curl beetle. It belongs to the scarab beetle family and is closely related to the cockchafer. June beetles reach a size between 14 and 18 millimeters and have yellow-brown to brown-colored wing covers. The vertex and pronotum are darker in color than the rest of the body.

What gave the beetles their official German name is the pattern on the wing covers. There are three raised ribs on each side. Noticeable are the long feelers, whose attached compartments are divided into three sections on closer inspection. The beetles are hairy on the pronotum and under the wings.

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Reproduction and stages of development

The beetles mate in June. The female lays up to 35 eggs in sandy soils in July. They fly back to the places where they hatched to lay their eggs. Shortly afterwards the female dies. The first larval stage hatches between July and August, depending on when the eggs are laid.

As soon as a larva hatches, it crawls into the substrate. To hibernate, the larvae shed their skin so that they survive the winter in the second larval stage. In order to be protected from the frosty temperatures, the grubs retreat below the frost line of the ground.

In June of the second year the grubs shed their skin in order to migrate back to the roots in the third larval stage. At this stage, the larvae survive the coming winter in deeper layers of the earth. In the third year, the grubs transform into a pupa from which the adult beetles hatch in June. In northern regions, full development takes up to four years.

The larval stages are so large:

• first stage : about one centimeter
• second stage : two to three centimeters
• third stage : up to five centimeters

Enemies

Bats are natural enemies of the flying beetles. The insectivorous mammals are active when the June beetles are at their peak. The larvae are eaten by shrews and moles. In near-natural gardens with different habitats, in which many different insect species find an optimal basis for life, the spread of the June beetle is regulated in a natural way.

Enemies living in and on the ground:

• Arthropods like stone creepers
• Parasite fly
• Dagger wasps
• Larvae of various ground beetles

Risk of confusion with other beetles

There are some species of beetle that can easily be confused with the June beetle. Since some other scarab beetles are also known as June beetles, there is often misunderstanding. However, it is important to clearly delimit species, as control measures can also endanger useful beetles.

Cockchafer and June beetle in comparison

The cockchafer most widespread in Central Europe is the field cockchafer (Melolontha melolontha). It also belongs to the scarab beetle family and lives in open landscapes. Its larvae need a well-loose soil with moist conditions. They often find optimal conditions in gardens, parks and meadows.

	Cockchafer	June beetle
size	22 to 32 millimeters	14 to 18 millimeters
Wing coverts	light or dark red-brown	yellow-brown
Hairiness	white, never opaque	brownish, densely bristled
Longitudinal ribs	four per wing cover	three per wing cover

Differentiation of the larvae

The grubs of May and June beetles are creamy white to white-yellow in color and have a brown head capsule. This makes it difficult to distinguish between the species, which makes targeted control more difficult. They have a typical posture that is reminiscent of a “c”. In order to separate the two types, the last abdominal segment must be examined more closely. In the cockchafer, this last link has an annular transverse furrow, so that the segment appears to be divided into two parts.

Another important difference between June beetles and cockchafer beetles is the anus column on the last segment. In the June beetle larvae, this is deeply incised and fanned out upwards with three rays. Cockchafer larvae have a shallow anal crevice.

July beetle

The species Anomala dubia, which is also known as the metallic July beetle, is hidden behind the July bug. The reason for this name is the metallic sheen of the head and pronotum, which shimmer green. Its elytra are colored light brown. This species also belongs to the scarab beetles and is between twelve and 15 millimeters long.

A typical distinguishing feature is the lack of hair, which distinguishes it from other garden leaf beetles. Like the June beetle, this species also lays its eggs in sandy soils. The grubs eat the roots of grass and trees, while the beetles feed on willow and birch leaves.

Activity of the July bugs:

• Flight time between May and August
• sunny days are preferred
• flies in the twilight

Rhizotrogus marginipes

This scarab beetle is sometimes referred to as the June beetle because there is no official German name for it. This species differs from the actual June beetle by the barely visible stripes on the wings. The pronotum is dark in color and roughly to finely dotted. The rest of the body is reddish-yellow to brownish in color. Rhizotrogus marginipes has an adjacent hairiness, while the June beetle is conspicuously hairy and long ciliate on the edges of the wing covers.

When the beetle flies:

• between June and July
• in the evening
• preferably on cool days

What do June bugs eat?

On the menu of the larvae living in the ground, there are fine roots of grass, wild herbs and ornamental plants in the garden. They do not specialize in any plant species and eat away at the roots of cyclamen, wild grape, primroses or azaleas. The roots of woody plants such as roses and rhododendrons or freshly planted deciduous trees and pines are also eaten by the grubs. Adult June beetles eat leaves and flowers from deciduous trees such as fruit trees.

Where do June bugs live?

June beetles live on the edges of forests and on arable land. They prefer semi-open landscapes and can therefore also be found in gardens or parks with stands of trees and in avenues. Southern Norway and central Sweden represent the northern limit of the range of this scarab beetle, because it needs warm temperatures. June beetles occur only locally in the mountains. The females look for sandy and well loosened soils for laying eggs. You avoid damp locations.

When do June bugs appear?

The flight time of the June beetles extends from June to July, which is why the species got its common German name. The beetles are not diurnal and prefer warm temperatures. On mild summer evenings, the beetles go looking for food and partners. In particularly mild winter months, the larvae pupate at the end of winter, so that June beetles can appear in April in a few years. They swarm out in large numbers, which is why they are often associated with a beetle plague. About two-thirds of the flying beetles are male.

Male June bugs swarm around garden furniture, trees and bushes on mild summer evenings around June 21st because they are looking for a partner.

Digression

Flying June beetle

These scarab beetles are considered to be clumsy fliers because it is not uncommon for them to accidentally land on clothing. This is because the animals orientate themselves on the higher silhouettes in front of the open horizon. People can easily be mistaken for a tree. Another reason for the clumsy behavior are the comparatively small wings that have to carry a lot of weight. Maneuverability in flight suffers from this unequal ratio.

Harmful and useful larvae

The adult June beetle does not pose a threat to woody plants, even if they swarm out in large numbers and eat leaves. After a few weeks, the beetles disappear as quickly as they appeared, so that deciduous trees and fruit bushes can recover from the damage caused by eating in a short time.

The larvae can, however, affect lawns or beds. New planting of trees is also threatened. If the grubs eat roots, the affected plants can no longer supply themselves with sufficient nutrients and water. They die over time. Since the grubs of various harmful and beneficial species are very similar, you need to distinguish the species from one another before controlling.

Grub	coloring	food	particularities
Rose chafer	white with a grayish shade	dead plant remains	crawling stretched out on his back
Rhinoceros beetle	whitish with a light brown head	dead plant remains	up to 10 cm long
Garden leaf beetles	whitish with brown head	living parts of plants	crawling stretched out on his stomach

Damage

The greatest danger for the plants comes from the larvae in the third stage, as they eat a lot of food. The first warning signal is stunted growth in grasses that occurs selectively in the lawn. Circular spots with dried up grass are a typical indication of grubs in the ground. The dead areas can be peeled off with the bare hand, which reveals the nests of the larvae.

Consequential damage:

• churned up ground by wild boars
• areas picked by birds
• Molehills

Digression

June bugs and culture

Children are confronted with the June beetle in kindergarten and primary school. It serves as a template for coloring pictures and appears in memos that children can use to discover the months. In order to take away the fear of the animals, trapping campaigns are carried out in many schools. Children can examine the beetles closely and learn how they differentiate them from cockchafer. With the help of cliparts or collages, the children can depict the brown fallow beetles in their natural habitat.

frequently asked Questions

Are June bugs dangerous?

There is no danger from flying June beetles, even if you pick them up. Many people are scared when the beetles fly straight towards them. But the fear of a bite is unfounded. The animals do not sting, are not poisonous and do not suck blood. Even if your pet has eaten a June beetle, you don't have to worry. Cats like to eat junk bugs as a snack when they pursue their natural hunting instinct.

Do junk bugs build nests?

Due to the massive occurrence of the beetles on warm summer evenings, the assumption can be made that June beetles live in nests. But the beetles do not build a shelter. They lay their eggs on the bare ground, provided that it is sandy enough. After the larvae hatch, they retreat into the substrate for further development. The adult beetles eventually crawl out of the ground again.

When do June bugs disappear?

The only reason a beetle can survive is to reproduce, which is why their lifespan is very short. After this is done and the females have laid their eggs, the June beetles die within the same year.

Where does the June beetle come from?

The scarab beetles are warmth-loving and colonize open habitats that are warmed by the sun. They go to gardens more often and do not shy away from built-up areas, as these are more protected and retain heat. In order for the animals to survive, uneven lawns, sandy soils and trees and bushes are important sources of food.

How long do June bugs stay?

June bugs love warmth, which is why they mainly appear in the summer months. If the winter months are particularly mild, the larvae can pupate as early as April. The adult beetles then fly out much earlier to look for food and find a partner. They don't fly in rainy weather. The massive occurrence lasts a few weeks.

What is the lifespan of the June beetle?

The beetles don't get very old. After they hatch, the beetles can expect a lifespan of four to six weeks. This range can vary slightly depending on the weather.

Where do June bugs live during the day?

So that the clumsy fliers are better protected from predators such as birds and mammals, they have moved their activity to dusk. Your flight will last a few hours. Afterwards, June bugs hide in the low vegetation again, where they spend the day.