Tackling fungal diseases

Taken from The Northern Farmer, March 2017, written by Wendy Short

 

Cereal crops have come through the winter well in the North, but growers must keep on top of fungal diseases in order to maximise yield potential this season.


Winter cereal crops in the north-west have fared well over the winter, following favourable conditions at sowing time, with many having already achieved some considerable growth, according to Simon Nelson of Agrovista, who covers Cumbria and Dumfriesshire.


"We had a mild autumn and reasonably good conditions for drilling,” he said. “This got the majority of cereal crops off to a good start and they are now well advanced. Winter barley has made the most progress, as in this region it is generally sown before winter wheat, which tends to follow grass.


"Some crops have performed so well that I have been asked whether they should be grazed by sheep, to curtail their growth, but this is not something I would recommend, as it would cause a serious setback. The next job will be to apply nitrogen, ideally in early March, unless the weather turns very cold and wet."


The most troublesome yield robber in the west of the England is septoria, which thrives in the damp climate, said Mr Nelson. "Losses due to septoria can be severe, because it strips the green area of the plant. It is so prevalent that it is rare to walk through a field and find no evidence of the disease."

 

Mr Nelson strongly advised the use of SDHI chemistry, to control fungal diseases, and timing is critical, he stressed.


"SDID fungicides must be included in disease treatment programmes. At least one application is required and ideally, crops should receive two. The most robust regime is to use an SDHI product at growth stage 32 and again at the flag leaf stage.


"SDHI chemistry is significantly more expensive, compared with the triazoles. However, I feel they are well worth the additional expense, particularly as a number of triazoles are becoming less effective at septoria at lower rates. There is also a risk that we may lose access to some of the products in the future," said Mr Nelson.

 

NIABTAG's Patrick Stephenson paints a similar picture of over-wintered cereals in the North-East, but believes that cheaper triazole chemistry still has its place in some farm spray programmes. While septoria is a concern, yellow rust could also threaten crop performance, he predicted.


"Most growers had the opportunity to drill at the optimum time, although sowing was slightly later on farms south of the Humber, due to efforts to control blackgrass," said Mr Stephenson. "Crops are generally looking very healthy and have tillered well.


"Breeders have made great strides in plant breeding and there are a number of varieties with good resistance to fungal disease; KWS Siskin and Syngenta's Graham would be two examples in the wheat sector.


"This trait gives us another weapon to use in disease control and careful varietial choice can permit a lower-cost spray programme, which could include the triazoles.

 

Septoria is a recurrent issue, but was more yellow rust about last season than I have seen in a while.  I believe this was caused by a combination of the weather, which created favourable conditions for the disease to take hold, and a prevalence of varieties which were susceptible to infection. The problem was compounded, because varietal disease resistance ratings can vary from year to year."


SDHIs can also be used at varying strengths for controlling rust and they have a mode of action, compared with the triazoles, which offers a possible benefit, he added.


"SDHIs have a role to play, but at 70 per cent of field rate usage, they are still more ex­ pensive than tiazole chemistry.


"Decisions will come down to individual growers and their situations, but it is worth considering cheaper combinations and alternatives and reduced rates of application. I would also add that I feel there is no need to rush on to fields to apply nitrogen this spring," said Mr Stephenson.

 

17 March 2017

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