The pollen beetle does not have a good reputation. He can turn beautiful summer months into a torment. If you cycle past rapeseed fields, hundreds of insects are often attracted to them. To fight the beetle in your own garden, simple home remedies are usually sufficient.

Pollen beetles have specialized in pollen from rape and other yellow flowers

Table of Contents

Show all
  1. the essentials in brief
  2. Pollen beetle - control
  3. Fight with home remedies
  4. Damage caused by pollen beetle
  5. Are pollen beetles dangerous?
  6. Identify pollen beetles
  7. habitat and way of life
  8. frequently asked Questions

    9. the essentials in brief

    • In agriculture, pollen beetles are usually controlled with pyrethroids. The sprays are now proving to be ineffective.
    • Before chemical agents are used, the benefits should be weighed. Home remedies or beneficial insects are gentler and more effective.
    • Pollen pollen beetles leave typical feeding damage on oilseed rape. The damage threshold is an orientation value from which control measures should be initiated.
    • The insects can be clearly identified by their activity in typical habitats. Although they are increasingly spreading, they are harmless to humans.

    How can I combat pollen beetle?

    The example of the pollen beetle has shown that chemical agents do not solve the problem of pest infestation, but are ineffective in the worst case. Therefore, follow important instructions before you reach for sprays from the garden center.

    spray

    Pyrethroids also kill all other insects

    In the last 20 years, the pollen beetle has been controlled almost exclusively with pyrethroids. As the insects move through a sprayed crop they come into direct contact with the insecticide. After a short time, the beetles show disoriented behavior. Their movements are no longer rhythmic, which is comparable to staggering. They eventually fall to the ground and die.

    Problems when using pyrethroids:

    • Washing out by rain possible
    • Active ingredient degrades in strong sunlight
    • work less well at temperatures below five and above 15 degrees
    • Insecticide does not act selectively, but kills all insects

    digression:
    In the past ten years, a declining effectiveness of pyrethroids has been observed across Europe. The pollen beetle is increasingly unimpressed by the use of the spray. Laboratory tests found that the beetles have developed an enzyme to break down the toxin.

    The main reason for this development is the fact that in the past only pyrethroids were used. If the mechanism of action is always the same, the beetles that are less susceptible survive. The proportion of insensitive insects increases, so that the agent becomes less and less effective.

    Tips for handling chemical agents

    The chemical club should only be used in extreme emergencies, because the toxic substances cause further problems. Not only do they have a negative impact on the environment, but they can also affect health. Your own garden should be a space for relaxation and provide safe food. Therefore, consider these tips before any countermeasures:

    • sit out: a bad weather period after a high automatically displaces the beetles
    • control: count beetles per plant every morning to determine control effectiveness
    • Questioning: each use of insecticides should be checked for necessity

    Pollen beetle - home remedies that help

    In agriculture, further methods of control are being discussed, which have so far only been used to a limited extent in practice. Alternative means are the use of parasitic fungi, beneficial insects or catch plants. In ecological cultivation and in private gardens, the beetle can be fought with gentle household remedies. Reflective materials such as milk of lime or straw are intended to drive the pollen beetle away. They are applied to field edges in northern Germany, so that the immigration of the beetles is delayed.

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    collect

    Beetle harvesters are common on farms that control pests biologically. In the home garden, collecting by hand has the same effect. With this measure, the infestation pressure can be reduced by about 30 percent, so that there is no further need for action for ornamental and crop plants.

    rock flour

    Dusting substances are spread on the oilseed rape plants before bud development begins. For the greatest possible success, you should use the remedy for the first time when the temperature threshold of ten degrees Celsius is exceeded. Another application occurs after the appearance of the first flower buds. Rock flour (€14.13) prevents the beetle from eating through the plant tissue. Timely application can reduce infestation by a third. You can either sprinkle the flour by hand or mix and sprinkle with water.

    vegetable oils

    In order to reduce the immigration of beetles from the edge of the field, the edge areas are sprayed with rapeseed or sunflower oil. The solubility of unformulated vegetable oils is increased by adding a neutral soap. In English laboratory tests it was found that the female pollen beetle reacts sensitively to lavender oil. It has a strong repellent effect on insects.

    parasitic wasps

    Ichneumon wasps (€22.99) are very helpful in the fight against pollen beetles

    The insects prove to be useful pest controllers, which can reduce the larvae population of the pollen beetle by more than 50 percent. In order to promote parasitic wasps in your own garden, natural structures are essential. In general, these ensure greater biodiversity and ensure optimal living conditions for the natural enemies of oilseed rape pests.

    Habitat for parasitic wasps:

    • flowering hedges
    • rotten tree trunks with retreat niches
    • species-rich walls in a sunny location
    • Stripes of wildflowers in the meadow

    What damage do pollen beetles leave behind?

    In the spring, pollen beetles go in search of food. They feed on pollen, which is inside the rapeseed buds. The harmful insect causes visible feeding marks, which extend over the entire plant population in the case of a heavy infestation. Small buds are completely eaten away, while larger buds show the typical pitting. Badly damaged buds will show yellowing and will slowly dry up until they fall off the stem. If feeding damage is minor, stunted flowers and misshapen or twisted pods will develop.

    damage threshold

    The control threshold is a value for orientation as to when control makes sense. This value changes over the course of the vegetation period, since the plants are better able to cope with feeding damage as they get older. Therefore, the damage threshold at the beginning of bud development is lower than just before the flower opens. Count the beetles on each plant to help decide on possible control. The infestation is determined between March and April.

    harmless population combat useful
    Buds are very small one or two insects three to four beetles
    14 days before flowering three to four insects seven to eight beetles
    Bud is about to open five to six insects more than eight bugs

    Are pollen beetles dangerous?

    Pollen pollen beetles only bite flowers, not human skin

    The crop pests are widespread in the summer months. They settle on light-colored clothing and bath towels and become a nuisance when cycling. The insects bite - but humans do not have to fear a sting or bite from the pollen beetle. They only eat their way through plant tissue to get the coveted pollen.

    If you are cycling when the weather is nice and do not want to attract bugs, you should make sure that you wear dark clothing. Light-colored shirts and pants are attractive to the insects. They mistake yellow clothing for a bright flower.

    Although pollen beetles can become a nuisance in summer, they do not pose a threat to humans.

    spread in recent years

    In recent years, the weather has favored the spread of the small black insects. The pollen beetle found optimal living conditions in 2022, as temperatures rose to the optimal range early in the year. In windless conditions and sunny conditions, a particularly large number of insects can hatch at the same time, which can quickly lead to a plague.

    The pollen beetle was a much-discussed insect in 2022. New insecticide strategies have been developed as a result of the numerous reports of increasing resistance to pyrethroids. They should mitigate the build-up of resistance. New agents for controlling the pollen beetle have been approved since spring 2022.

    Identify pollen beetles

    The little beetles look very cute

    The insect has the scientific name Brassicogethes aeneus. Its English name, common pollen beetle, suggests its preferred food. Rape pollen beetles belong to the pollen beetle family, of which 140 to 150 species are known in Central Europe.

    Look

    The beetles reach a size between 1.5 and 2.5 millimeters. They have a shell made of chitin, which is usually black in color and has a metallic sheen. Occasionally, specimens with blue, green, or violet base tones can be observed. Legs and antennae stand out in color from the oval-shaped body. They appear in dark brown tones. The short antennae resemble a club due to their thickened shape. On closer inspection, small hairs can be seen on the elytra.

    lifespan

    After the beetles hatch in the year they lay their eggs, they spend the rest of the year searching for food. From the end of August, the insects fly near the edges of forests to look for suitable winter quarters there. They overwinter in the loose layer of humus in forests or hedges. When the sun warms the ground next spring, the insects will leave their hiding place. They will be around 14 months old.

    tips

    Adverse weather conditions can increase the mortality rate. Wait for rainfall and low pressure areas. Wind also drives away the pests.

    habitat and way of life

    Pollen beetles like yellow

    Pollen pollen beetles have specialized in the color yellow. In years with favorable weather conditions, they can spread en masse despite their natural enemies. Birds find a protein-rich treat in the little black beetles. The main enemies of beetles are parasites.

    activity

    Pollen beetles fly at temperatures between 10 and 15 degrees Celsius. They prefer sunny conditions and windless conditions. Mild weather can encourage the beetles to spread particularly early. The insects are diurnal and prefer to fly to rapeseed fields.

    Since they do not feed exclusively on oilseed rape, pollen beetle also occur on other plants with yellow petals. They feed on pollen and can also destroy the pistils and ovary of the flowers. If the flowers are not yet open, the beetles eat their way through the bud leaves to the inside. Their larvae feed exclusively on pollen and do not destroy any flower organs.

    Happen

    Pollen pollen beetles are found not only in Europe but also in North Africa, Asia and North America. They find optimal living conditions in open and bushy landscapes. Since the beetles prefer to fly to yellow flowering plants, they can also be observed in the garden or on the balcony. They perch on flowers and buds of oilseed rape plants and fly towards yellow-flowering cruciferous plants or plants from other families such as nasturtium. If the bugs appear in the apartment or house, there is no need to worry. You got lost through open windows and doors.

    tips

    Pollen beetles don't seem to like the smell of lemongrass. Fresh lemongrass stalks are ideal for scaring away.

    frequently asked Questions

    How can I prevent the pollen beetle from spreading?

    Create optimal growth conditions for your plants and prevent waterlogging or soil compaction. Coordinated fertilization and gentle tillage promote rapid flowering. The beetles migrate into the fields from the edge. Create large and compact beds instead of small narrow strips to keep feeding damage to a minimum.

    Manure application can also reduce feeding damage if applied in dry weather. Avoid growing summer oilseed rape and instead choose early-flowering oilseed rape varieties. Due to their faster flower development, these varieties are less damaged.

    How do rape pollen beetles develop?

    The females bore a hole in vigorously developed buds from below to lay their eggs near the stamens. A few days later, the larvae hatch and find good feeding conditions. They feed on pollen and do not harm the plant.

    The larvae molt several times and drop to the ground in the last larval instar. They live in the substrate for the next three to four weeks to pupate. When the rape blossoms, the new generation of beetles hatch. The air temperature can drop to nine degrees Celsius.

    How do rape pollen beetles overwinter?

    From the end of August, when temperatures gradually drop and the food supply dwindles, this year's generation of beetles swarm out. They fly to sheltered hedgerows and forest edges in search of suitable winter quarters. You will find this in a loosened soil with coarse material. They leave their hiding place next spring when the air temperature rises above ten degrees Celsius.

    Are there effective attractants that attract pollen beetles?

    Since rape pollen beetles do not only fly on rape but generally on yellow-flowering cruciferous plants, other cultivated plants can serve as lures. The diurnal beetles colonize a rapeseed field by penetrating over the edges inwards. A six to forty meter wide border strip of turnips or early flowering cruciferous vegetables running around the entire field distracts the beetles from the main crop.

    In this way, the rapeseed is protected during the critical development phase. Because of the way the beetles live, oilseed rape should be grown in large and compact plots. This reduces the damage caused by feeding.

Category:

Animals in the garden