The pollen beetle can not only damage the rapeseed harvest. It can also cause considerable damage to various useful and ornamental plants in the home garden
Have you ever driven past a rapeseed field and been bothered by a swarm of small black beetles? It was almost certainly the pollen beetle. This can cause considerable damage to the rapeseed plants and does not stop at vegetable plants, ornamental shrubs and roses. So it is not unusual if you discover the small beetles in your own garden. We'll show you some ways to get rid of the pests.
Recognize pollen beetle
Rapeseed beetles belong to the 140 to 150 species of pollen beetles. They reach a size of 1.5 to 2.5 millimeters. The elongated-oval body is protected by a shiny chitin armor that can shimmer black, blue, green or violet. Both the legs and the club-shaped antennae are colored brown.
Larvae hatch from elongated, milky white eggs, which can reach a length of up to four millimeters. The yellowish to white larvae have three short, dark-colored pairs of legs and a black-brown head. In addition, several small dark spots can be seen on the body.
Danger of the pollen beetle
Rape pollen beetles overwinter in the layer of leaves or the turf at a depth of about two to five centimetres. As soon as the ground temperatures reach over 10 degrees, they leave their winter quarters. From an air temperature of 15 degrees, the beetles go in search of food and mainly colonize rapeseed fields. Here they are after the pollen that is inside the flower buds. In order to get to the desired pollen, the pollen beetle has to bite through the flower buds that are still closed. In doing so, they often also injure the ovary and thus destroy the entire bud. They then dry up and fall off. Only the empty flower stalks remain.
Tip: As soon as the rapeseed is in bloom, there is no longer any significant damage from the beetles.
Rape pollen beetles attack other cruciferous plants and roses in addition to rape. And also do in front of ornamental shrubsDon't stop. You can do a lot of damage, especially in the vegetable patch.
Fighting the pollen beetle
The common method of controlling the pollen beetle is the use of chemical insecticides. These bring not only one disadvantage. On the one hand, the beetles develop resistance to the agents used, making them completely useless. On the other hand, the insecticides are not specifically effective against the pollen beetle, but against all insects.
If you want to fight the beetle in your own garden, you should use more environmentally friendly methods.
Collect pollen beetle
A first effective measure in the fight against the voracious beetles can be to collect them from your plants in early spring. You will only catch a fraction of the bugs. But you can reduce the infestation to such an extent that the beetles can no longer cause much damage.
Vegetable oil soap solution keeps bugs away
Make a solution of vegetable oil, a neutral soap and water. If you spray the edges of beds with it, you can reduce the number of immigrating pests. Make sure, however, that you use pure curd or soft soap.
Rock flour stops feeding
Many hobby gardeners are familiar with rock dust as a natural fertilizer. In addition, they are used in pest control - including the pollen beetle. The rock flour has an immediate effect and inhibits the feeding of beetles and larvae.
You should first apply the rock flour when the buds begin to form and then again just before flowering. This can be done either dry with a powder syringe or dissolved in water with a spray bottle.
Tip: Depending on the weather, further treatments may be necessary. Because both rain and strong wind impair the effect of the rock flour.
Parasitic wasps as natural predators
Pest control with parasitic wasps is really recommended. They are natural predators of the pollen beetle, which can reduce the larvae population by more than 50 percent. They lay their eggs in the larvae of the beetles. Later, a new generation of parasitic wasps hatch from the larvae.
You can get parasitic wasps commercially, but these are not suitable for use in the garden. However, you can lure the beneficial insects into the garden by creating suitable retreats:
- Walls planted with species in a sunny location
- rotten and hollow tree trunks
- Wildflower strips on the meadow
- flowering hedges
Neem as a natural crop protection
You can find various neem-containing products on the market that you can use against sucking and biting pests such as the pollen beetle:
Prevent damage from the pollen beetle
You have a number of options to prevent as far as possible an infestation by the pollen beetle. The most important measure is to create optimal growth conditions for your plants. Avoid compacted soils or locations that tend to waterlogging. In addition, you can stimulate the growth of the plants with good fertilization and thus promote rapid flowering. If an infestation does occur, the damage will not be as great.
As a second measure, you can apply rock flour or unpolluted liquid manure to the plants in early spring. In this way, you not only give your plants very good fertilization. At the same time you drive away approaching pollen beetles.
You should also make sure that you do not plant your crops in small, narrow beds. Because, as already mentioned, the voracious beetles work their way in from the edge. Therefore, plant the largest possible beds with a larger number of plants. In this way, the damage caused by an infestation can be limited.
You should also be careful when working the soil. Because not only the pollen beetle overwinters in the soil, but also a variety of useful insects - including ladybirds and parasitic wasps, which eat the larvae of the pollen beetle. It is therefore better to work the soil by hand or at least with a small tool.