South: Decision time for blackgrass control

All the autumn drilling, except the winter beans, is now complete. For this late drilling time, increase the winter wheat seed rate to no less than 300 seeds/sq m. The early drilled winter wheat is at the tillering stage GS 22 and the mid-October drilled crops are at GS 14. The majority of the winter barley is at the 5-leaf stage GS 15. Winter oats are at the 1-2 leaf stage.


The residual herbicides applied pre-emergent seem to be working well, albeit rather slowly. Volunteer oilseed rape and beans have come through the residuals and will need controlling. Since straight Mecoprop may not be used in the autumn, consider using Pixie (mecoprop + diflufenican). Thor (tribenuron) may also be used to control volunteer rape.


Where it has not been possible to apply a pre-emergence herbicide, or where the blackgrass has come through the first treatment, the only option is to apply Atlantis (iodosulfuron + mesosulfuron) + Biopower (Wetter) before the blackgrass gets to beyond the 3-leaf stage. The conditions at the moment seem to be ideal for application of Atlantis. 

Oilseed rape is at the 4-6 leaf stage. Crops sprayed for phoma around the middle of October with Capitan (flusilazole) or Proline (prothioconazole) are clean of any disease. But further monitoring is required with the wet weather around, and almost certainly a second fungicide spray will be required. Also look out for light leaf spot, which is becoming more problematic in the south west.


Blackgrass and sterile brome in the oilseed rape crop are coming through thick and fast. The soil temperature is too high at present to apply Precis (propyzamide) and needs to be below 7-8C for this chemical to work effectively.


But where the blackgrass is bigger than the 3-leaf stage, then it is appropriate to apply Precis at the full rate now, lest the weather breaks and it is not possible to apply this treatment resulting in the blackgrass getting too deep rooted to achieve an effective control.


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