- Young winter rapeseed seedlings are exposed to the first pest attacks.
- Warm and sunny weather favors the development of many species.
- It is imperative to start regular inspections of plantations in order to detect threats in time.
Rapeseed sowing began around mid-August and is still ongoing locally (plantations requiring reseeding). The first pests are appearing on plantations that have already been rowed, which is a signal for regular inspections of the plantations.
– Flea beetles have already appeared and the damage they cause is visible (leaves with sieve-like holes). The first aphids are already there – mainly the peach aphid, and the cabbage aphid is less numerous. This carries the risk of the plantation being infected with turnip yellows viruses – says Dr. hab. Przemysła Strażyński from IOR-PIB in Poznań to the farmer.pl portal.
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Flea beetles have been attacking rapeseed since its inception. How to combat them?
Limited label entries
Therefore, plantations should be monitored in order to react in time with a foliar insecticide. As Dr. Strażynski notes, when choosing a preparation, it is worth paying attention to the label information, because they are limited in terms of the range of species controlled.
– According to the guidelines in the labels of insecticides currently registered for the control of aphids in winter rape, they should be used in accordance with the signals when aphids invade the plantation or after the first colonies are detected. However, there is a need to update the labels, because most of them refer to the cabbage aphid – notes the scientist.
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Locally difficult rape emergence. How to break the soil crust?
Catch crops and self-seeds are a source of danger
In the agricultural area, many so-called green bridges for pests are maintained after the harvest, mainly those that create several generations in the season. For rape, the green bridge is created by species such as white mustard or oil radish, i.e. those that often appear in intercrop crops. A source of danger is also rape volunteers and weeds from the cabbage family. Harmful species reproduce on them.
– On self-sown seedlings (unplowed stubble, plants from seeds scattered during transport) we have a whole range of autumn rape pests. In addition to flea beetles and aphids, caterpillars of the diamondback moth, whiteflies and caterpillars of white cabbage moths feed on them en masse. In time, they will move to the plantations – points out Dr. Strażynski.
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High temperatures deepen drought. Rapeseed with difficult emergence
There is already a joke with the second generation
One of the dangerous pests for rapeseed is the cabbage stem moth, which can severely damage rapeseed roots.
As reported by IOR-PIB in Poznań in a phytosanitary report, in the last ten days of August, increased activity of the second-year generation of cabbage rootworm was noted in Skierniewice fields with cabbage.
– The number of caught individuals/1 trap was on average on 20.08. – 27 individuals; 21.08 – 39 individuals, and 22.08 – 20 individuals – informed IOR-PIB.
It is worth mentioning here that the most dangerous for rapeseed is the third generation of the leaf miner, which appears most often at the turn of September and October. During this period, generations II and III often overlap. This poses a threat to young plants, which lasts practically until November.
Monitoring for the occurrence of cabbage root fly is very important, because the treatment of this pest makes the most sense if it is carried out during the numerous fly raids on plantations. The best way to monitor cabbage root fly raids is by putting out yellow dishes.
Note on the phenomenon of resistance and temperature
An important issue regarding the use of chemicals is
possibility of developing pest resistance to insecticides.
Unfortunately, there are only a few active substances registered for the control of autumn pests, which make it difficult to perform proper protection that takes into account rotation. When deciding on a treatment, it is also worth paying attention to temperatures. The current heat (temperatures above 20 degrees Celsius) limit the effect of pyrethroids.
Economic damage thresholds for autumn rapeseed pests
During the inspection, attention should also be paid to the number of pests. Autumn pests appear on the plantation every year with varying intensity and treatment is not always necessary. When deciding on this step, one can use the thresholds of economic damage established for individual species (table).
Table: Economic damage thresholds for autumn pests occurring in rapeseed around emergence
Species Observation date Harm threshold Rapeseed flea beetle
September, October (BBCH 12–19) 3 beetles per 1 m of the Flea order
earth after emergence
(BBCH 10–15) 1 beetle per 1 m of row Agricultural plant emergence
(BBCH 9–16) 6–8 caterpillars per 1 m2 Snails
immediately after sowing and during emergence (BBCH 8–11)
in the 1–4 leaf stage and in later stages (BBCH 11–15)
2–3 snails on average per trap, destroying 5% of plants
4 or more snails on average per trap, 10% of plants destroyed severely or very severely
The Bonebreaker
winter rapeseed rape:
September, October
(BBCH 11–19) 1 caterpillar on 1 plant Dantniś
crusader September – October
(BBCH 12–19) 1 caterpillar on 1 plant Cabbage fly September–November
(BBCH 15–19) 1 yellow bowl of cream in 3 days Chowacz
Galls September – October
(BBCH 12–19) 2–3 beetles in a yellow pot within 3 days Peach aphid September – November (BBCH 11–19) 5–6 aphids on 10 plants