Talking Agronomy: Chris Martin, Tackling a dynamic disease season

Article taken from the Arable Farming

As we start to think about fungicide programmes in winter cereals, it's vital we get the programme off to a good start in order to stay ahead of the incredibly dynamic disease complex.

The days have gone where we can rescue the situation with reliable eradicant chemistry; so it's vitally important as we start our programmes off; to ensure we remain in protective mode.

Following the unusually mild winter, disease is already at high levels in crops. Septoria tritici can easily be found on the older leaves of pretty much all wheat crops, regardless of variety ratings. Yellow rust can be easily found in variety trial plots, as well as on a field scale on the usual suspect varieties, particularly nearer the east coast of the region.

Whether these diseases will turn into an epidemic, or fail to thrive, will depend on the weather conditions throughout April and May. But obviously we have to decide how to start off our fungicide programmes before we know what the spring weather has to offer.

Hindsight glasses would be the only way of accurately predicting the perfect fungicide strategy, but the evidence from the last couple of seasons would stress the need to front load the programme to ensure you remain in a protective scenario. If we get it wrong early in the programme and allow active disease in the crop prior to the flag leaf timing, because of the evolution of key diseases such as septoria tritici we can no longer consistently eradicate them, and yield will be significantly suppressed.

While looking back in history is always dangerous, particularly now with the mutations, we still can learn some lessons from last year, in particular with regard to timing. Many crops were particularly forward across the region this time last year, as they are this year, with the exception of later-sown crops.


On these forward crops last year, many
appeared to reach GS30 by mid-March, with the ear significantly moving up the stem. This triggered some TO spraying. The weather then cooled down and final leaf 3 did not fully emerge across the region in many varieties until early May. This meant, in many cases, a minimum six-week gap between the supposed TO, which despite appearing to be GS30, was actually only coating final leaf 5  at best. Unless it was used as a specific pre-TO yellow rust 'clean up spray; it was probably not cost-effective. I fit wasn't followed up with a correctly timed TO at  final leaf 4in early to mid-April, it could have seriously compromised  the whole fungicide programme.

Using the acronym 'PALMAT' will give you the best chance of maximising potential from your fungicide programme while also trying to combat fungicide resistance:

 

Prevention: Remaining in a protective mode throughout the season.

Alternation: Using the whole chemistry set still available is vital. SDHI, triazoles, strobilurins, morpho­ lines and multi-sites all have key roles to play.

Limitation: Ensuring no more than two applications of SDHI or strobilurins in order to reduce the risk of selecting for further resistance.

Mixture: Where possible try and use at least three different modes of action.

Application: Optimise application. The higher the disease pressure, the more important this becomes.

Timing: There is no substitute for correct timing. Timing can be as important as or even more important than fungicide choice. It is worth highlighting high risk fields which you may need to prioritise to time correctly. Itis definitely time well spent using a sharp scalpel and dissecting plants to ensure you are coating the target leaf.

Agronomist facts:
Chris Martin is a technical manager for Agrovista, based in the north east of England.  His role is to provide technical advice to growers over an area extending from Lincolnshire to Scotland.  Prior to this, he was an agronomist with the company for 15 years and continues to provide agronomy advice to a number of growers producing combinable crops in the Scotch Corner area.

 

04 April 2017

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