The main species and their methods of control

Zoological determination of leaf beetles.

With a total of around 50,000 species described so far, the leaf beetles, zoologically Chrysomelidae, form one of the largest families of beetles in the world. They are common in all zoolographic areas of the world with the exception of the arctic zones. In Germany there are around 520 species of the 50,000.

Look

Although the different species may seem quite diverse at first glance, they have some similarities at the meta-level in terms of physique and coloration.

The adults are generally of medium size in relation to the beetle world and have an egg-shaped, sometimes more elongated, sometimes more rounded, arched shape. Their length is between one and 18 millimeters. In relation to the torso, your head is rather small, rounded and mostly flush with the torso via a curved pronotum, so that it typically appears squat.

Many leaf beetle species are characterized by a conspicuous, sometimes artfully patterned and often metallic sheen color. The magnificent leaf beetle is a prime example in this respect: with its greenish-yellowish, blue to copper-colored changing, metallic shimmering color, which completely covers his body up to the legs and the antennae, he almost looks like one Jewel. Others, for example the golden earth flea, appear like a precious coin with their copper-golden, strongly shiny color. The Colorado beetle, on the other hand, impresses with its distinctive yellow-black stripe pattern.

way of life

The adults usually mate several times with different sexual partners and produce several generations of larvae per year. The females lay their eggs individually or in groups or rows on the forage plants, depending on the species, often protected in shallow, gnawed hollows or covered under a layer of feces. Some leaf beetle species also prefer to feed on aquatic plants. Some of their brood can therefore also be found underwater in gelatinous shells.

The larvae usually hatch after a few days and pupate into adult beetles within a few days.

The forage plants - and thus also the plants susceptible to infestation - differ depending on the leaf beetle species. Some are oliophagous, so they prefer only one or a few specific plants. This plant-relatedness is often also reflected in the species name. In the case of some species, if they occur more frequently, it can cause immense damage. Colorado beetles can devour entire fields

Relevant leaf beetle species for gardeners and farmers.

Given the enormous biodiversity of leaf beetles in Germany alone, we cannot describe all of them here. We therefore want to concentrate on a few species that are of increased relevance for hobby gardeners and farmers. The following leaf beetles are common in our country and play a bigger role as pests:

• Poplar leaf beetle
• Lily Chicken
• Colorado potato beetle
• Red-necked corn beetle
• Lily pad beetle

Here is an overview of their respective appearance so that you can determine the pests, differentiate them from one another and initiate suitable control measures:

Fight leaf beetles.

The best way to protect your plants from leaf beetles depends on the type of leaf beetle and the extent of the infestation.

Poplar leaf beetle

Poplar leaf beetles can be a problem, especially in monocultures and in warm, dry years. Poplars on avenues are then sometimes downright eaten bare and massive tree losses can occur. Aspens in particular are preferred by poplar leaf beetles, but willows can also be attacked by them.

Because the poplar leaf beetles cannot fly well, the best preventive measure against their infestation is to create mixed cultures instead of monocultures. The beetles stay on a tree as long as there are leaves and move around as little as necessary. Only when the tree is bare do they look for another one. However, if a suitable predator cannot be found soon, the beetles will starve to death while searching.

If an infestation is already present, the best way to contain it is to disturb the beetles that hibernate in the ground under the tree by raking up the soil and, if necessary, killing them.

For the control with insecticides only 6 agents based on pyrethrins, acetamiprid or thiachloprid are currently approved.

Lily Chicken

The actually very pretty, seal-lacquer red beetles with the equally pretty name are the most common lily pests in Europe and Eurasia. They prefer to attack beautiful and giant lilies, but also checkerboard flowers and chives. As with most pests, the larvae cause the greatest damage because of their enormous feeding activity.

The females lay their orange-red eggs in groups on the underside of the leaves, where the larvae begin to eat after hatching. The infestation can be recognized by feeding traces, but also by the striking red adults and the larvae covered with black droppings. They cover themselves with their droppings to protect themselves from predators.

The most direct method of controlling lily chickens is to collect the adults, preferably in the morning when they are still stiff and stiff sluggish are. Because they let themselves fall in danger and with the harder-to-see, dark belly side up land, it is also advisable to spread a net under the lily and target the beetles to shake off. The larvae can be sprayed off the plant with a sharp jet of water.

If the infestation is severe, insecticides can also help against biting and sucking pests.

Colorado potato beetle

The Colorado potato beetle originally comes from central Mexico and later spread to the USA as a result of the large-scale potato cultivation by white settlers. The pests were discovered via seed potatoes as early as the mid-19th century. Century to Europe, first to England and the Netherlands. Soon afterwards, in 1877, the first specimens were also seen in Germany.

Digression

The Colorado beetle invasion

In the course of the 20th In the early 1900s, Colorado beetles quickly became a real nuisance. In 1935, the so-called KAD, the Colorado beetle defense service, was founded in the German Reich because of its invasive spread. He needed a Colorado potato beetle primer and mobilized schoolchildren and the unemployed to fight against it with the appeal:

Be a fighter, don't be a sleeper, watch out for the Colorado beetle!

Today the Colorado potato beetle is widespread all over the world and can sometimes quickly devour entire fields. His preferred forage plants are of course the potatoes, on which he attacks different parts of the plant. But other vegetables and crops belonging to the nightshade family, such as aubergines, tomatoes, peppers and tobacco, can also be affected.

Numerous methods can be used to control the Colorado potato beetle. A combination of preventive and acute treatment measures is particularly helpful.

Preventive measures

First of all, you should encourage natural predators of the Colorado potato beetle, which are now quite common in this country: these include toads and ground beetles in particular. In the sowing and after germination, you should then cover your crops with crop protection nets. In principle, it also makes sense to strengthen the plants with a nettle manure spray treatment.

After one year of infestation, you should dig up the earth well as a preventive measure for the next year, as the beetles hibernate in it. In this sense, it is also helpful to keep potatoes in year after year Crop rotation to cultivate. This is also recommended for a balanced land use anyway.

Acute measures

If the fat beetles are already running around in abundance on the potato or pepper plants, it is best to collect them first. For larger acreages, you can also walk through the rows armed with a stick and knock down the pests. Like many leaf beetle species, they like to let themselves fall in danger and can then be collected in a net spread out on the ground beforehand. Mint broth or coffee grounds are supposed to drive the beetles away.

The use of the bacterial preparation Bacilllus thuringiensis, which is toxic to beetles, but not to humans and plants, can be quite effective. The neem oil, which is widely used in organic horticulture, is also effective against the Colorado potato beetle.

Red-necked corn beetle

Because, according to its name, it prefers to eat cereals such as wheat, barley or oats, the red-necked beetle is a problem especially for farmers. They also attack fodder grasses, and occasionally maize. The larvae eat elongated holes in the leaves of the grass and can cause significant harvest losses.

Red-necked cereal leafet beetles can be contained relatively well with natural predators. Ladybugs, ground beetles, Lacewing larvae, Predatory bugs and parasitic wasps. For certain anti-skinning insecticides, a certain damage threshold, which is defined for each country, must be reached.

Lily pad beetle

Water lily leaf beetles belong to the leaf beetle species with an affinity for water plants. They are therefore particularly problematic for ornamental gardeners who maintain a pond with aquatic plants. Water lily leaf beetles not only infest the white water lily, but also other aquatic plants such as the yellow pond rose, the water knotweed, the swamp blood-eye or the common Arrowhead. But strawberries are also part of their forage plants, which is why they are also called strawberry beetles.

The adults and larvae of the water lily beetles live on the tops of the leaves of their host plants and live quite dangerously there. Because they cannot swim or breathe underwater. Therefore, if you discover an infestation, the safest method of control is to submerge the leaves. The larvae and possibly also the adult animals drown in the process.

frequently asked Questions

Which leaf beetle species are there?

In total, the leaf beetle family comprises around 50,000 species. In Germany, however, there are only about 520 species. The most common of these are the magnificent leaf beetle, the Colorado potato beetle, the plantain leaf beetle, the Poplar leaf beetles, the lily chickens, the common asparagus chickens, the shield and willow leaf beetles or the Hawthorn leaf beetle.

How do I identify leaf beetle species?

Some of the native leaf beetle species are easy, some more difficult to identify. The Colorado potato beetle or the magnificent leaf beetle are striped with their pale yellow-black or bluish-greenish to copper-colored and shimmering violet color very easily recognize. The lily chicken is also very noticeable with its sealing lacquer red back, but it is of the similar looking one Lily of the valley chicken to distinguish, the underside of which is not black, but also red. The flat, round, light green tortoise beetles, which are very similar to one another, are more difficult to identify.

Are leaf beetles pests?

The most relevant pests in this country are the Colorado potato beetle, the poplar leaf beetle, the red-necked corn beetle, the common asparagus or the lily chicken. They sometimes cause great damage in vegetable growing and ornamental gardens.

Which measures are suitable for controlling leaf beetles?

The different species of leaf beetles are fought in different ways. In the case of the most common species such as the Colorado beetle or the lily chicken, a common method is to collect or shake off and catch the adults in nets. Larvae can be effectively sprayed from the plants with a sharp jet of water. Infestation populations can also be contained by natural predators such as parasitic wasps, ground beetles, lacewings or ladybugs. In severe cases, certain bacterial preparations, neem oil or pesticides can be used as biological or chemical insecticides.

How do I recognize leaf beetle eggs and larvae?

The eggs of the most common leaf beetle species are usually found in groups on the underside of the leaves of their host plants. Depending on the type of beetle, they have different colors. The larvae also have their own appearance depending on the species. Those of the Colorado potato beetle, for example, have a stocky, isle-like ribbed body and a light red color with dotted sides. The larvae of the lily chickens are noticeable because they are wrapped in their own dark droppings, which they use to protect themselves against predators. They look like little piles of tar on the leaves. The larvae of lily pad beetles stand out from the green leaf tops of the infested aquatic plants because of their black color.