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The colza beetle (Brassicogethes aeneus) belongs to the family of glossy beetles (Nitidulidae). It occurs in Europe, North Africa, North America as well as in Asia. Its oval shaped body is up to 2.5 millimeters long. Particularly striking is his blue-green, shiny metallic back. The eggs of the pest are oblong and milky. Its yellowish-white larvae have a slim, about 4 millimeters long, little bristled body. You can see the juveniles on their black-brown head and the three short black-brown colored pairs of legs. On each section of the body, up to three dark spots are visible.
From a soil temperature of about 10 degrees Celsius leaves the canola beetle his winter quarters. When the daytime temperature rises to over 15 degrees Celsius, the little animals finally fly to the rape fields, where they first populate their edges. With sufficient sun and heat, however, the pest can spread quickly over the entire stock.
For oviposition, the female drills a small hole in the base of the buds of the affected plants. Here the animal then lays one to six eggs on the stamens inside. Only a few days later, the offspring of the rape beetle hatches. The young larvae feed mainly on pollen and nectar. After another three to four weeks, when the larvae have developed sufficiently, the small animals fall to the ground and pupate here in small chambers. At the end of July and June, the beetle generation hatches. The adult rape beetles eat different plants and look for a suitable winter storage again at the end of August - this can be, for example, under the litter of deciduous forests. Every year, one generation of the pest occurs.
In order to reach the popular pollen before the rape blossom, the rapeseed beetle must bite the flower buds. This results in different sized holes: Small buds are completely bitten, larger have visible feed holes. Damaged buds turn yellow, dry up and fall off as a result - only the empty flower and pod stems persist. If the buds do not drop off, the less affected parts of the plant have twists and cripples. With the beginning of the rape blossom usually no appreciable damages arise more.
The extent of rape beetle infestation depends on the weather. In a cold weather and a late rape flower the beetle destroys many buds, in warm summers with an early flowering, however, the risk of damage is rather low, since enough other pollen plant serve the rapeseed beetle as a food source.
Importance as a pest in agriculture
In addition to a variety of different host plants, the canola beetle feeds most - as the name suggests - of oilseed rape (Brassica napus). Often, the summer rape is affected by its later flower development more damage than the winter rape. But also in the seed cultivation of cruciferous vegetables as well as in oil radish (Raphanus sativus var. Oleiformis), turnip (Brassica rapa) and radish (Raphanus sativus var. Sativus) it can come to an infestation with the rape beetle. After blooming of rape fields, the pest may also attack Rosenfelder. There you will find the annoying beetle
Especially yellow and white rose petals are endangered in the garden
But not every plant takes an infestation with the rapeseed beetle so simple: The winter rape, for example, attempts to compensate for the resulting bud loss by reacting with an increased lateral shoot and bud formation on the damage caused by the rapeseed pest.
In order to avoid economic damage in agriculture, the rape beetle should be detected early and, if the harmful wave is exceeded, be combated immediately before the first open flowers appear.
In order to take precautionary measures against the canola beetle, there are various possibilities. First and foremost, create good growth conditions for your plants. Sites with waterlogging or soil compaction should be avoided. Optimal fertilization and soil tillage promote rapid growth with rapid flowering. This will reduce any possible damage caused by the canola beetle.
In agriculture, the addition of manure at the bud stage or on the rape plant scattered rock flour offer as a preventive measure. Since the beetles migrate from the edge into the fields, large, compact plots are recommended. There is less damage here than on a small, narrow area. A strip of planted turnips at the edge of the field also attracts the pest away from the rape culture, so that susceptible plants are protected from infestation for some time.
Rapeseed beetles are regulated by natural enemies both during pupation and in winter quarters. A plow-less tillage spares beneficial insects such as parasitic wasps, ladybug species and larvae of netflies. Encourage the little helpers, because they especially like to eat the larvae of the rapeseed beetle.
Fight colza beetles
In commercial cultivation, highly effective insecticides such as "Avaunt" and "Plenum 50 WG" are used in the bud stage of oilseed rape. Both remedies act as a contact and feeding poison and are only to be used outside the bee's flight. Beetle harvesting machines, reflective materials such as straw or milk of lime, and vegetable oils against the canola beetle are used in organic farming.