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July 2017

Your canola crop has been planted and has established well. What do you need to focus on in the production season?

The focus should be on post emergence weed management, fertilisers and disease control. When it comes to post emergence weed control, the type of canola will play a critical role in your choice of herbicides, especially in broadleaf weed control.

If you have planted a conventional cultivar you will not be able to apply a broadleaf herbicide because it will kill your crop as well. Clearfield (Cl) and Triazine tolerant (TT) canola has been modified to tolerate specific herbicides when it comes to the control of broadleaf weeds. Cysure (herbicide) can be used in Clearfield cultivars, while atrazine and simazine is compatible with TT cultivars. By using canola in your crop rotation you are able to deal with possible grass weed problems in your fields more effectively. Once the canola crop has grown to a stage where the soil is covered, the crops compete well with any possible weeds.

The next focus point is fertilisers. Depending upon seasonal rainfall, you can decide to apply once-off topdressing, with a possible second one later in the season. It is very important to make sure that the topdressing you apply contains Sulphur (S). Canola has a high S need and it plays an important role in the formation of oil in the seed. The nitrogen (N) amount applied can vary between 30 kg and 40kg of N per ha. The first topdressing can be applied with 4 to 6 weeks after emergence. A second topdressing of 30 kg of N/ha can be applied at stem elongation. It is also very important to apply boron. This element plays an important role in the forming of the flowers and eventually the number of pods, and should be applied no later than 10% flowering.

Disease control is the third aspect to focus on. Although the cultivars we use in South Africa are bred with varying degrees of Blackleg resistance, it is still necessary to apply a fungicide to control this disease. This should be done at the 4 to 6 leaf stage. Specific fungicides are registered for use in canola. The other disease that needs attention is Sclerotinia. This disease also has to be controlled by use of a fungicide, but only needs to be applied when the crop is at 30% flowering. Again, be careful to only use registered products.

The three aspects covered in this article are really important to ensure that you give your canola crop a good opportunity to produce a good yield.

Article submitted by Dr Johann Strauss, Directorate Plant Sciences, Research and Technology Development Services, Western Cape Department of Agriculture. For more information, send an email to johannst@elsenburg.com.

Publication: July 2017

Section: Pula/Imvula