In the rapeseed field, tiny glossy beetles cause serious crop failures. Indoors, rape beetles target flowering houseplants. Read here how you can recognize the pests by their appearance. Tried-and-tested tips and tricks reveal how you can get rid of rapeseed beetles in your home. This is how poison-free control in the garden works.
How can you fight rape beetles in your home and garden?
Rape beetles (Brassicogethes aeneus) are small, shiny metallic pests that can cause crop failures in rapeseed fields and attack houseplants. Lemon scent and a yellow water trap are suitable for combating in the apartment; in the garden, collecting, rock dust and natural predators such as parasitic wasps and ladybirds can help.
- Rape beetles are oval, 2 mm small, have a blue, green, black or purple, shiny metallic shell.
- Home remedies for rape beetles in the apartment are lemon scent and a yellow trap with water and detergent.
- Biological control agents in the garden are rock dust, collecting, shaking off and yellow peel as well as the predators parasitic wasps and ladybirds.
What do rape beetles look like?
Rape beetles (Brassicogethes aeneus) belong to the shiner beetle family and are usually called rapeseed beetles. The beetles can be recognized by their oval body, 1.5 to 2.5 millimeters long. What is striking is a shiny metallic chitin shell that shimmers blue, black, green or violet. The legs and club-shaped antennae are brown.
Yellowish-white larvae are slender, 4 millimeters long and sport short bristles. Three short, black-brown legs on each side of the body and a brown head characterize its appearance. Rapeseed beetle larvae hatch from milky-white, tiny eggs and shed their skin several times.
Why are rapeseed beetles harmful?
Rape beetles are accused of two habits. Menus and family planning nip any sympathy in the bud among farmers, hobbyists and indoor gardeners. A look at their lifestyle makes it clear why the shiny mini beetles are classified as pests:
Disastrous reproduction strategy
Rape beetles lay their eggs in buds
When the soil temperature reaches 10° Celsius, rape beetles become active and leave their winter quarters under a layer of leaves or turf. Starved, the glossy beetles fly to young plants for an extensive supply of leaves, flowers, pollen and nectar. On warm spring days with 18° Celsius and more, mass flights with a plague character are not uncommon. Immediately afterwards, rapeseed beetles devote themselves to their fatal reproduction strategy in these steps:
- Mated females bite a hole in buds
- 1 to 6 eggs per bud are laid on stamens and pistils
- The larvae hatch within 4 to 7 days
- The larvae eat nectar and pollen for 27 to 30 days
- Damage: eaten, dried, empty buds, premature flower fall, stunted, puny pods
Adult larvae drop to the ground, burrow two to three centimeters deep and pupate. After about two weeks, the young rape beetles emerge from their pupal cradle. This process takes place in June, just before or during the rapeseed harvest. The young beetles maturate on various wild and cultivated plants before heading to their winter quarters in August.
Numerous food and host plants
Roses are also attacked by rape beetles
Rapeseed is the preferred, but not the only, plant that rape beetles cast a covetous eye on. Cruciferous vegetables with yellow or white flowers are primarily affected. The following table lists typical crops and ornamental plants that suffer from a plague:
| Useful plants | Botanical name | Ornamental plants | Botanical name | Wild herbs | Botanical name |
|---|---|---|---|---|---|
| Raps | Brassica napus | Roses | Pink | Goose cress | Arabis |
| Rübsen | Brassica rapa | Gold lacquer | Erysimum suffruticosum | White Mustard | Sinapis alba |
| Radish | Raphanus raphanistrum | Scented Stones | Lobularia maritima | Barbara herb | Barbarea vulgaris |
| Radish | Raphanus sativus | Ribbon Flowers | Iberis | Shepherd's Purse | Capsella |
| Vegetable cabbage | Brassica oleracea | Night violets | Hesperis | Schöterich | Erysimum |
The real damage is caused by adult rape beetles when they eat the buds in spring or bite holes in the bottom of the buds. Larvae feed exclusively on pollen and nectar, which does not seriously damage the affected plants.
Tip
Yellow plates are useless for determining infestations and combating rapeseed beetles. The beetles are attracted by the bright yellow color. In contrast to cherry fruit flies and other pests, rape beetles do not stick to the special glue with their chitin shell. For this purpose there are special yellow trays with a close-meshed grid as a cover so that bees and other insects do not fall into them.
What to do against rape beetles in the house?
Rape beetles are stubborn fellows that don't like to be driven away. The beetles often find their way into the house, well hidden in the bouquet of wildflowers you have picked yourself. If you have discovered rapeseed beetles in your home, you do not have to tolerate the uninvited guests. The following two home remedies have proven to be effective for fighting without poison. How to get rid of rape beetles indoors:
Lemon scent
It is thanks to the persistent research of experienced entomologists (insectologists) that the lemon scent can drive away rape beetles. The following home remedies will drive away the pests forever:
- Lemongrass
- Lemon slices
- Shells filled with lemon juice
- Citronella products, such as soap, candles (€11.00 on Amazon), fragrance oil
Positive side effect: other nuisances and pests in the house, such as ants, spiders or mosquitoes, flee from the smell of lemon.
The following video impressively demonstrates why the scent of lemon has a deterrent effect on rape beetles:
Make your own rapeseed beetle trap
Your preference for the color yellow becomes a disaster for rape beetles when a self-made trap is used. The trap is copied from the yellow peel that farmers use to detect infestation in rapeseed fields. Take a yellow bowl, either made of plastic or glass. Fill the bowl halfway with water and add a drop of detergent to break the surface tension. If you place the trap near infested plants, the beetles will not be able to resist the attraction for long, will fall into the water and drown.
What helps against rape beetles in the garden?
Removing rape beetles manually is tedious but effective
Rape beetles don't mind if rapeseed doesn't grow in the garden. If the favorite plant is not available, the beetles quickly set their sights on useful plants and flower beauties. Primarily cruciferous vegetables, especially types of vegetable cabbage, are very popular with pests as a food source and nursery. Rapeseed beetles ruthlessly eat rose petals in the flower bed. Insecticides are not approved for home gardens and do not achieve any significant results anyway. The following overview sums up what really helps against rape beetles in the garden:
- Collecting: collect the cold-resistant rape beetles with two fingers early in the morning
- Shake it off: Spread out the foil and shake off any crawling bugs
- Rock dust: dust affected plants thinly with rock dust
- Engage predators: Birds, parasitic wasps, ladybirds
A mulch made of straw reflects the sun's rays and irritates rapeseed beetles when they approach. The effectiveness of vegetable oil solutions as a natural control agent is controversially discussed in private allotments. Buds sprayed with oil and water stick together, making it difficult for them to open. The milk of lime, which is promoted as a control agent in some instructions, is tricky to use because it is lime dissolved in water, which is primarily used as a wall coating and actually has no place in a natural garden.
Excursus
Attract parasitic wasps – end the rape beetle plague
Parasitic wasps are a miracle weapon in the fight against rape beetles
Parasitic wasps are the secret heroes in the fight against a plague of rape beetles. The delicate insects parasitize the larvae and reduce the infestation pressure in the field and bed by up to 50 percent. So far, nine parasitic wasp species are known in Europe and are helpful to farmers and hobby gardeners in combating rapeseed beetles. To ensure that beneficial insects find their way into your garden, it is important to consistently avoid all types of pesticides. Umbelliferous plants invite parasitic wasps to linger, such as parsley, fennel, carrots or hogweed. The delicate natural beauties cannot resist a self-made insect hotel.
Frequently asked questions
How to get rid of rape beetles in the apartment?
To drive rape beetles out of your home, lemony scents have proven to be effective. If you lay out lemon slices, add lemon juice to the mopping water or place lemongrass in the house, rape beetles will run away. A tried and tested home remedy against rape beetles in the home is yellow bowls that you fill with water and a drop of dishwashing liquid.
How long do rape beetles live?
As a rule, rape beetles live about 14 months. Rapeseed beetles overwinter once in their life in leaf litter and loose soil layers. In early spring, the beetles leave their winter quarters and first dedicate themselves to feeding on ripening rapeseed and spring flowers. Mated females soon lay their eggs in buds and flowers. Once a female beetle has laid her 250 to 400 eggs, her life is coming to an end.
Can rape beetles bite?
Rape beetles have powerful mouthparts for feeding and laying eggs in buds. Considering a body size of 2 millimeters, the teeth are tiny. The teeth are at least enough to bite into delicate flowers and young leaves. The attempt to bite into human skin is, of course, doomed to failure for rape beetles.
What helps against a rape beetle plague in the rose garden?
If droves of rape beetles infest the rose garden, we recommend an XXL version of the yellow trap, which works well in the apartment. Purchase one yellow bucket for every 10 to 20 square feet of infested area. Fill this bucket two-thirds full with water and one to two tablespoons of dish soap. Cover each bucket with a close-mesh screen (8mm x 8mm) to prevent bees from falling into it. Rapeseed beetles are attracted to the yellow color and sink into the water because the detergent breaks the surface tension. Replace contaminated water.
Can rape beetles fly?
Yes, rape beetles have a well-developed flight system. The shiny metallic chitin shell protects transparent wings that carry a rapeseed beetle through the air for up to 3 kilometers. This is a major reason why home gardens near rapeseed fields often have to contend with a plague of beetles in vegetables and rose beds.
Tip
Seven-spot ladybirds (Coccinella septempunctata) like to eat rape beetle larvae. Have there been too few of the red lucky beetles with their distinctive spots in your garden? Then you can increase the population of beneficial insects and breed ladybugs yourself. Breeding farms and specialist retailers offer complete breeding sets with eggs or ladybird larvae.
