If you discover feeding holes in the leaves of plants, the tortoiseshell beetle could be the culprit. You can find out how to recognize and combat this here.
The leaf beetles come in Central Europe in about 30 subspecies. These are very similar and are difficult for the layperson to tell apart. Optically, the shield beetles are therefore often mistaken for bugs. However, the shield beetle has some special features that make it unique.
For example, the beetle has some strange peculiarities that make it easy to recognize. For example, the females lay their eggs on the underside of the leaves. These are covered with a secretion. The larvae have a habit of covering themselves with their own feces for camouflage. For the hobby gardener, this can be recognized by a dark heap.
How to recognize the tortoiseshell beetle?
The tortoiseshell beetle belongs to the leaf beetles and is part of the Cassidinae subfamily. In our latitudes, the beetles reach a length of between half a centimeter and one centimeter. The body is strongly flattened and has a slightly oval shape. The head is covered by a broad pronotum. In addition, tortoiseshell beetles are green or brownish in color and are therefore very well adapted to their environment.
The larvae of the tortoiseshell beetle, on the other hand, can be recognized by their light green color and the small spines sticking out at the sides.
What kind of damage does the shield beetle leave behind?
Mature shield beetles leave conspicuous feeding holes on the leaves of infested plants. If nibbled leaf edges become visible, these do not come from the beetle itself, but from the larvae. Often, however, the larvae only gnaw off a few layers of the leaves, not making complete holes. The sheet then only appears thinner in its structure. This is referred to as the so-called window eating.
What types of tortoise beetles are there?
In Central Europe alone there are three genera with around 30 species. Some common tortoise beetle species are presented in the following overview:
| Tortoiseshell beetle | Size and Occurrence | Special Features |
|---|---|---|
| Rusty Shield Beetle | • 5.5 to 7mm • Scandinavia to Mediterranean • Turkey, China, Japan | • reddish brown colouring • pronotum golden green colouring • light colored legs |
| Red-edged Flat Beetle | • 7 to 10 mm • Altitudes up to 2,500 meters • on trunks of conifers • Bavaria, Brandenburg, Saxony | • flat physique • dark brown color • considered a jungle relic • insensitive to cold |
| Gold-Striped Shield Beetle | • 4 to 4.5 mm • Mediterranean to Arctic Circle • Japan | • Elytra shiny longitudinally striped • Elytra and pronotum form bell-like body cover |
| Toddler Beetle | • 6 to 7 mm • Europe • North America | • yellow-brown colouring • elytra black patterned • underside of body black |
Which plants are usually affected?
From the end of April, hobby gardeners should keep an eye out for the pests. Then the tortoise beetles wake up from their hibernation and leave the ground. The damage is limited to the leaves, but can lead to a permanent weakening of the plants, even to death. The following plant species are particularly endangered:
- Sunflowers
- Daisies
- Lavender
- Mint
- sage
- Stinging Nettles
- thistles
- Hollow Tooth
- Ziest
- Leet
- Thyme
- Savory
Asteraceae and lamiaceae are particularly endangered.
What can you do to prevent a tortoise beetle infestation?
If the tortoiseshell beetle is up to mischief in the herb and vegetable patch, chemical pesticides are out of the question. An alternative is offered by natural means that can be used quite effectively to combat an infestation with tortoiseshell beetles. For example, you can try the following remedies.
❍ Use nettle manure against shield beetles:
Stinging nettle manure is a reliable tonic and plant protection agent. The nettle manure is made in a few simple steps:
- Collect fresh nettles (about a kilogram).
- Chop nettles into small pieces.
- Pour about ten liters of water over the nettle sections.
- Stir vigorously.
- Cover the jar.
- Leave the nettle manure to soak for about two weeks.
- Stir daily.
Tip:
An unpleasant odor develops during fermentation. This can be minimized by adding rock flour, loam or compost.
Before use, the nettle liquid manure is sieved. Then dilute the finished nettle manure with water in a ratio of 1:10. You can then water the affected plants with it. If the plants are not to be eaten, spraying is also possible.
❍ Use neem oil against shield beetles:
Many home gardeners have discovered neem oil as a miracle weapon against pests and to strengthen garden plants. This is a purely natural product, obtained from the seeds of the neem tree native to India. This neem oil works reliably against:
- Beetle
- caterpillars
- Snails
- spider mites
- Lice
- Mushrooms
To prevent tortoiseshell infestation, the diluted neem oil is sprayed directly onto the leaves. As an additive in the irrigation water, neem oil serves to strengthen the plant. By the way, the best time for treatment with neem oil is early in the morning.
Once you have sprayed the affected plant all over, you will need a little patience. The pests stop feeding on the leaves, but it can take a few days for the tortoiseshell beetles to disappear completely.
Important:
Treatment with neem oil should not be carried out in the rain or in strong sunlight. When it rains, the active ingredient is washed off, when the sun shines, the leaves threaten to burn.
❍ Use natural predators:
Even the well camouflaged shield beetles have enemies. The caterpillar fly, for example, devours the larvae of the tortoiseshell beetle. Even if the parasitic flies are common in Europe, you have to intervene and buy the beneficial insects in the garden store and apply them specifically to the infested plants.
How to prevent an infestation
➜ digging up ground:
Before spring sowing, it is helpful to dig up the soil and look for hibernating tortoiseshell beetles. Then remove these until you order the floor.
➜ Collect shield bugs:
Regular control of the beds is generally useful. In this way, traces of feeding can be recognized early and beetles and larvae can be collected. Collecting and shaking off works best early in the morning. Because when the temperatures are low in the morning, the warmth-loving tortoiseshell beetles are still clammy and quite immobile.
➜ Observe crop rotation:
To ensure the rapid spread of the infestationavoid, it is advisable not to cultivate lamiaceae in the immediate vicinity of composite plants. You can also prevent an infestation by following crop rotation.