Tillage Update on Oilseed Rape Desiccation and Potato Blight

Shay Phelan, Teagasc Crops and Potato specialist provides this week's tillage update. He has advice on how to decide if an Oilseed rape crop is ready for desiccation and the steps to take. He also discusses potato blight, Met Eireann's blight warning system and various fungicides which can be used

Main photo above: Oilseed rape pod ready for desiccation

Oilseed Rape Desiccation

Most crops will be ready for desiccation with glyphosate in the coming week or so, this will ensure an even ripening of the crop and control of any remaining weeds. When looking at the crop to try to decide if the crop is ready for desiccation or not, just follow these steps;  

• Sample the crop across the field and select the most representative areas. Select pods in the middle of the main raceme or on side branches, whichever is most representative. Pick 20 pods at random.
• If seed colour change from green to brown is seen in at least two thirds* of the seeds per pod in at least 15 of the pods picked, this is earliest correct stage for desiccation.
• Repeat the procedure in other areas of the crop to check that the assessment is applicable to the entire field. Spray within 4 days, unless the weather is very cool, then the window can be extended to 7 days.
• Use a high rate of Glyphosate when burning off OSR (e.g. Round-up Flex 3.0L/ha) and especially when targeting perennial weeds.
• Use 200-250 L/ha of water per hectare to get good coverage of the crop.
• A pod sealant (applied with the glyphosate) may be useful especially if harvest is delayed.
• An interval of 14-21 days is necessary before combine harvesting.
• If approximately half of the seeds are turning brown, the crop should be ready to spray in 3 days, but repeat the procedure to check that the correct stage has been reached. N.B. Spraying too early will lead to poor desiccation. 

Potato Blight

The recent rainfall should give some relief for those who are irrigating crops, however with the rain comes an increased risk of blight attack on crops so growers both commercial and part time should be on alert and walking crops regularly. There have already been reports of some crops in the south of the country being affected.

Met Eireann have a new blight warning system which is accessible to everyone and provides a more localised warning on a county by county basis similar to wind, rain, frost warnings that we are all familiar with.

This warning can be accessed on the following link: Blight forecast

Pictured below; Blight warning map from Met Eireann

All growers should apply a suitable fungicide on a weekly basis unless you are using either of the Zorvec products which have a 10 day interval. Most crops are coming towards the end of the rapid canopy phase so continue to use systemic products such as Infinito or Zorvec before switching on to Revus, Ranman Top, etc. in another week or so. If blight is seen in a crop include Cymoxanil, (Option, Cymbal etc. ) at full rates for some knockdown effect. Intervals may have to be tighter i.e. 3-4 days in some cases to get on top of the problem.

The Tillage Edge Podcast

On this week's Tillage Edge podcast, Mark Plunkett and Dermot Forristal from Teagasc, discuss the value of straw and how best to incorporate straw this year.  Listen below.

For more episodes and information from the Tillage Edge podcast go to: www.teagasc.ie/thetillageedge

Find out more information and advice from the Teagasc Crops team here.   The Teagasc Crops Specialists issue an article on a topic of interest to tillage farmers every Thursday on Teagasc Daily.  Find your local Teagasc office here