Expert advice

How to control rape self-seeders?

The decisive majority of winter rape plantations have already solved the problem of dicots in the autumn using pre-emergence or post-emergence treatments. Most plant protection products, despite the present unfavourable weather conditions, are working satisfactorily, hence, there is no need to perform corrective treatments in the spring.

The field sees individual, rare weeds that do not hinder the growing of rape, and are below the threshold of economic harm. In the autumn as well, the majority of farmers have undertaken attempts at controlling monocots – primarily cereal self-seeders. This applies mainly to plantations, on which the presence of cereal self-seeders was high, and which practically prevented the correct emergence and development of rape following emergence. In case of strong competition from monocots, rape is unable to develop an appropriate leaf system, instead just becoming high. The growth cone is erected and becomes particularly susceptible to freezing in case there is no snow cover. The overly thick and dense field in a tie of warm autumn and winter decidedly worsens the phytosanitary conditions – disease pressure increases.

A second group includes farmers who have not yet performed any dicot control treatments on their fields because their pressure in the autumn was not too strong, and they waited to do this in the spring. In such a case we recommend performing the treatment using Labrador 05 EC at 1.1-1.2 l/ hectare. The dose should be selected following a field inspection, however due to the quite warm autumn and winter, monocots could have entered higher development phases – one must keep that in mind. Herbicidal treatment should be performed immediately following the commencement of growth.

We recommend the treatment even if the presence of self-seeders is low, because in time, they may find their place, grow and thicken. Their presence in the further part of the growing season may cause worse ventilation and slower desiccation of the field, and as a result, fungal diseases may develop more intensely. Cereal self-seeders are the most common monocots present in winter rape plantations. Labrador 05 EC also controls couch grass and the black twitch – we recommend the higher of the recommended doses for the control of these weed types. A treatment using Labrador 05 EC may already be performed if temperatures exceed 5-7 °C, and if they are maintained at this level over most of 24 hours. The product is taken up by leaves of the monocots. It may be estimated that within an hour post treatment, the plant takes up a sufficient amount of the active agent to achieve satisfactory effectiveness, however, it is best if rainfall does not occur three hours after treatment.

The initial weed control effect is visible after ca. ten days, and complete monocot removal occurs after approx. three weeks. High temperatures facilitate the visual effect of weed control and complete death of self-seeders is visible already after two weeks. In order for the winter rape plantation to be managed well – in order for rape to winter well without losses despite lack of snow cover, and in order for the growth cone to be found low – one must perform the fungicidal treatment properly and control the plant form. In the autumn, the pressure of self-seeders was not excessively high, however, a warm autumn and winter had caused the tillering of individual plants and new growths. If the air temperature reaches the necessary minimum levels, perform the treatment using Labrador 05 EC at 1.2l/ hectare.

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