- From what BBCH phase should rapeseed regulation begin?
- Adjustment in one or two treatments?
Early adjustment gives the best effect
The time at which we perform the first regulatory treatment is very important. It determines how the development of rapeseed will shape itself in the rest of the autumn. Too early application, as well as too late, have their impact on the course of vegetation.
And so, in principle, we start regulation at the earliest when rape has 4 true leaves (BBCH 14). These are relatively early stages, and the question is often asked: what about those plants that are still small because they started germination late? Well, the plantation condition, i.e. the development phase, can be different at one site. Nevertheless, if the majority of plants, about 70%, already have 4 leaves, then the treatment can be performed. Especially in the two-treatment technology, which is gaining importance during a long autumn. Then the application in the BBCH 14 phase is the first treatment, while in the BBCH 16-18 phase we start the second application. In such a system, we are talking about split-dose technology. It does not necessarily have to involve higher costs. This is because we can approach this issue in such a way that we divide the entire autumn dose into two treatments. However, in the case of a high probability of dynamic plant development, we can also apply, for example, 70% of the regulator dose (or fungicide with a regulatory function) in the first application, and similarly in the second. In this arrangement, the outlay on protection is slightly higher, although the savings on regulation are illusory, and last year was a perfect example of this.
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When to apply boron in rapeseed?
In split doses, regulation first, then fungicide?
In the two-treatment technology, in the first application we focus primarily on stronger regulation. Since there is currently no high disease pressure on rapeseed plantations, stronger regulation at the expense of slightly weaker fungicide protection may prove to be a good solution, but only in the first application. In the second treatment, the regulation may be slightly less aggressive, but we will have to focus more on fungicide protection. We went through such a scenario a year ago. Strong disease pressure was associated with the period from about mid-October. At that time, those plantations that were protected sequentially, i.e. in the second treatment in October or at the end of September, coped better. Treatments performed in mid-September no longer extended the protective umbrella when higher pathogen pressure appeared (first of all, the risk of infection with blackleg must be taken into account here).
So, in the first application, you can apply mepiqual chloride, which is a strong regulator. A combination with calcium prohexadione is also worth considering. However, these substances do not provide fungicide protection, so it is worth applying one of the triazoles (e.g. tebuconazole or metconazole – the latter of the triazoles has the strongest regulatory properties). In the regulatory treatment, difenoconazole and paclobutrazol also perform their tasks very well, although they are not very strong regulators, but they provide very good fungicide protection. In some proposals, we will also find recommendations for the use of strobilurins (e.g. pyraclostrobin). These do not act as retardants, but they spread a fairly long protective umbrella from the fungicide side.
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What about rapeseed flooded during the flood?
With one treatment you can wait, but not too long
If we plan to perform one regulatory treatment, we can wait until BBCH 15-16. Then the plants that started late will probably already have 3-4 leaves. But there is a certain risk associated with this. Namely, the larger the plants, the later the treatment with the implementation of retardants, the worse the regulatory effect. Therefore, it is best to plan this regulation already at the stage of 4-5 rape leaves, even if it is supposed to be the only autumn application. In good positions, in intensive technologies, a second treatment must be taken into account, which will often be a supplementary treatment. The second application will be conditioned by the weather and phytosanitary situation, and it will depend on these two factors whether it is necessary to regulate even more or focus more on fungicide protection. Nevertheless, remember that too late a regulatory treatment brings worse effects.
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