Leaf beetles are one of the largest beetle families in the world's fauna. The numerous different species have an astonishingly beautiful appearance. As herbivorous animals, many of them also have pest status for gardeners and farmers. We introduce you to the most important species.
How do I recognize and control leaf beetles?
Leaf beetles are a widespread family of beetles numbering around 50.000 species that mostly feed on plants. Well-known pests include the Colorado potato beetle, poplar leaf beetle, red-breasted grain hen and the lily hen. Collection, natural predators or, in severe cases, insecticides are suitable for combating.
Zoological identification of leaf beetles
With a total of around 50,000 species described so far, the leaf beetles, zoologically known as Chrysomelidae, are one of the largest beetle families in the world. They are distributed in all zoolographic areas of the world with the exception of the Arctic zones. Of the 50,000, around 520 species occur in Germany.
Appearance
Although the different species may seem quite diverse at first glance, they do share some similarities at the meta level in terms of body structure and coloration.
The adults are generally, in relation to the beetle world in general, of medium size and have an egg-shaped, sometimes more elongated, sometimes more rounded, curved shape. Their length is between one and 18 millimeters. Their head is rather small in relation to the torso, rounded and usually set off flush from the torso via a curved pronotum, which typically results in a stocky appearance.
Many leaf beetle species are characterized by a striking, sometimes artistically patterned and often shiny metallic color. The magnificent leaf beetle is a prime example in this regard: with its greenish-yellowish, blue to copper-colored, metallic shimmering coloration, which covers its body completely down to the legs and antennae, it almost looks like a jewel. Others, for example the golden flea beetle, appear like a valuable coin with their copper-gold, very shiny coloring. The Colorado potato beetle, on the other hand, impresses with its distinctive yellow-black striped pattern.
Lifestyle
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, often protected in shallow, gnawed hollows or covered under a layer of feces, depending on the species. Some leaf beetle species also prefer to feed on aquatic plants. Their brood can therefore sometimes be found underwater in gelatinous shells.
The larvae usually hatch after a few days and mature into adult beetles within a few days in pupation.
The forage plants - and therefore also the plants susceptible to infestation - vary depending on the leaf beetle species. Some are oliophagous, meaning they prefer only one or a few specific plants. This plant-relatedness is often reflected in the species name. For some species, it can cause immense damage if it occurs frequently. Colorado potato beetles can eat entire fields bare
Relevant leaf beetle species for gardeners and farmers
With the enormous diversity of leaf beetles in Germany alone, we cannot describe them all here. We therefore want to focus on a few species that are of increased relevance for hobby gardeners and farmers. The following leaf beetles are common here and play a larger role as pests:
- Poplar leaf beetle
- Lily Chicken
- Potato beetle
- Red-necked grain chicken
- Water lily leaf beetle
Here is an overview of their appearance so that you can identify the pests, distinguish them from each other and initiate suitable control measures:
| Poplar leaf beetle | Lily Chicken | Potato beetle | Red-necked grain chicken | Water lily leaf beetle | |
|---|---|---|---|---|---|
| Shape | ovoid to roundish, stocky | elongated, narrow pronotum, even narrower head | rounded, slightly narrower, downwardly curved pronotum and head | Elongated-narrow, pronotum of equal width, small head | elongated-narrow, pronotum of the same width, small head |
| Coloring | Wings brick red, head blackish to greenish, wings and legs black | Wings and pronotum sealing wax red and matt shiny, belly side, legs and antennae black | Longitudinal wings in light saffron yellow and black, neck plate dotted in the same colors, legs amber brown, feet black | Wings shiny black with dotted embossing, pronotum and legs maple syrup red, head and antennae black | Wings dull light brown, rather wrinkled surface, pronotum and legs pale amber, blackish spotted, head blackish |
| Size | 10-12 mm long | 6-8 mm long | 7-15 mm long | 4-4, 5 mm long | 6-7 mm long |
| Forage plants | Poplars (aspens), willows | Lilies, checkerboard flowers, chives | Potatoes, tomatoes, eggplant, tobacco, peppers | Wheat, barley, oats | Water lilies, yellow pond lilies, knotweed, strawberries |
| Combat | Caterpillar flies, parasitic wasps, raking up soil under poplar trees in winter | Collect, hose off larvae | Toads, ground beetles, culture protection nets, bacterial preparation, neem oil | Lady beetles, ground beetles, lacewings, parasitic wasps, predatory bugs | Submerge the leaves of the host aquatic plant for a longer period of time |
Blattkäfer im Garten
Fighting 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 prefer to attack poplar trees
Poplar leaf beetles can be a problem, especially in monocultures and in warm, dry years. Poplars on avenues are sometimes literally 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 poplar leaf beetles cannot fly well, the best preventive measure against their infestation is to create mixed rather than monocultures. The beetles stay on a tree as long as there are leaves and move as little as necessary. Only when the tree has been eaten bare do they look for another one. However, if a suitable victim cannot be found soon, the beetles starve while searching.
If an infestation is already present, the best way to contain it is to disturb and, if necessary, kill the beetles that overwinter in the ground under the tree by raking up the soil.
Only 6 products based on pyrethrins, acetamiprid or thiacloprid are currently approved for control with insecticides.
Lily Chicken
The lily chicken is very striking due to its strong color
The actually very pretty, sealing wax red beetles with the equally pretty name are the most widespread lily pests in Europe and Eurasia. They prefer to attack magnificent and giant lilies, but also checkerboard flowers and chives. As with most pests, the larvae cause the most damage because of their enormous feeding activity.
The females lay their orange-red eggs in groups on the undersides of the leaves, where the larvae begin to eat after hatching. The infestation can be recognized by traces of feeding, but also by the strikingly red adults and the larvae covered in black feces. They cover themselves with their droppings to protect themselves from predators.
The most direct method for combating lily chicks is to collect the adults, preferably in the morning when they are still stiff and lethargic. Because they drop when in danger and land with the dark side of their belly upwards, which is harder to see, it is also recommended to spread a net under the lily and shake the beetles off. The larvae can be sprayed off the plant with a sharp jet of water.
If the infestation is severe, insecticides also help against biting and sucking pests.
Potato beetle
The Colorado potato beetle is a serious danger
The Colorado potato beetle originally comes from central Mexico and later spread to the USA through large-scale potato cultivation by white settlers. The pests were introduced to Europe via seed potatoes in the mid-19th century, initially to England and the Netherlands. Soon afterwards, in 1877, the first specimens were spotted in Germany.
Excursus
The Invasion of the Colorado Beetle
In the course of the 20th century, Colorado potato beetles quickly became a real pest. In 1935, the so-called KAD, the Colorado potato beetle defense service, was founded in the German Reich because of its invasive spread. He needed a Colorado potato beetle primer and mobilized school children and the unemployed to fight it with the call:
Be a fighter, don't be a sleeper, watch out for the Colorado potato beetle!
Today the Colorado potato beetle is widespread all over the world and can sometimes devour entire fields in a short period of time. Its preferred food plants are of course potatoes, on which it attacks various parts of the plant. But other vegetables and crops belonging to the nightshade family, such as eggplants, tomatoes, peppers and tobacco, can also be affected.
Numerous methods can be used to combat the Colorado potato beetle. A combination of preventative and acute treatment measures is particularly helpful.
Preventive measures
First of all, you should encourage natural predators of the Colorado potato beetle, which now exist in this country: these primarily include toads and ground beetles. When sowing and after germination, you should cover your crops with cultural protection nets. In principle, it also makes sense to strengthen the plants with a nettle spray treatment.
After a year of infestation, you should dig up the soil well for the next year as a preventive measure, as the beetles overwinter in it. In this sense, it is also helpful to cultivate potatoes in crop rotation year after year. This is also recommended for balanced land use anyway.
Acute measures
If there are already lots of big beetles running around on the potato or pepper plants, it's best to collect them first. For larger cultivation areas, you can also walk through the rows armed with a stick and knock down the pests. Like many species of leaf beetles, they like to drop when threatened and can then be collected in a net spread out on the ground. Mint broth or coffee grounds should drive away the beetles.
The use of the bacterial preparation Bacilllus thuringiensis, which is toxic to the beetles but not to humans and plants, can be quite effective. Neem oil, which is often used in organic gardening, also works against Colorado potato beetles.
Red-necked grain chicken
The red-necked grain chicken loves wheat, barley and co.
Because, according to its name, it prefers to eat grains such as wheat, barley or oats, the red-necked grain chicken is particularly a problem for farmers. They also attack forage grasses, and occasionally also corn. The larvae eat elongated holes in the leaves of the grass and can cause significant crop losses.
With natural predators, red-necked grain chickens can be contained relatively well. Ladybugs, ground beetles, lacewing larvae, predatory bugs and parasitic wasps are particularly hungry for them. For certain anti-molting insecticides, a certain damage threshold must be reached, which is defined for each country.
Water lily leaf beetle
The lily leaf beetle loves aquatic plants
Water lily leaf beetles are among the leaf beetle species that have an affinity for aquatic plants. They are therefore particularly problematic for ornamental gardeners who maintain a pond with aquatic plants. Water lily leaf beetles not only attack the white water lily, but also other aquatic plants such as the yellow pond lily, the water knotweed, the marsh bloodeye or the common arrowhead. But strawberries are also one of their food 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 there quite dangerously. Because they cannot swim or breathe underwater. If you notice an infestation, the safest control method is to submerge the leaves. The larvae and possibly also the adults drown.
Tip
A longer diving phase is safest. To do this, you can weigh down the leaves with a structural steel mat.
Frequently asked questions
What species of leaf beetles are there?
In total, the leaf beetle family includes around 50,000 species. In Germany, however, there are only around 520 species. The most common of these are the magnificent leaf beetle, the Colorado potato beetle, the plantain leaf beetle, the poplar leaf beetle, the lily leaf beetle, the common asparagus leaf beetle, 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 to identify, some are more difficult. The Colorado potato beetle or the magnificent leaf beetle are very easy to recognize with their pale yellow-black striped or bluish-greenish to coppery and purple shimmering coloring. The lily chicken is also very striking with its sealing wax red back, but can be distinguished from the similar looking lily of the valley chicken, whose underside is not black, but also red. The flat, round, light green shield beetle variants, which are very similar to one another, are particularly 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 grain chicken, the common asparagus chicken and the lily chicken. They sometimes cause great damage to vegetable production and ornamental gardens.
Which measures are suitable for leaf beetle control?
The different species of leaf beetles are combated in different ways. For the most common species, such as the Colorado potato beetle or the lily beetle, collecting or shaking off the adults and collecting them in nets is a common method. Larvae can be effectively sprayed from plants with a sharp jet of water. Infestation populations can also be easily contained by natural predators such as parasitic wasps, ground beetles, lacewings or ladybirds. 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 leaf beetle species most common in our country usually sit in groups on the undersides 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 squat, isopod-like ribbed body and a light red color with dots on the sides. The larvae of the lily chickens are noticeable because they are covered in their own dark feces, which they use to protect themselves against predators. On the leaves they look like little piles of tar. The larvae of water lily leaf beetles stand out conspicuously from the green tops of the leaves of the infected aquatic plants due to their black color.
