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New fungicides and better varieties to help in the fight against septoria

22 August 2019

The wet end to the 2019 wheat season has helped to drive septoria levels in wheat crops and it is already evident that there has been further slippage in the efficacy of existing chemistry.

Untreated plots of Viscount at the SRUC trial site in East Lothian – septoria

SRUC trial results for this season show the promise of new chemistry and the issues with the old.  The new azole fungicide Revysol and the novel active Inatreq will be with us soon and, despite the many challenges of bringing new products to market, there are also a couple of other fungicides in the pipeline further back which show promise. This is all very positive news for growers but the fall-off in performance this year in our existing chemistry is both a current and future concern. Without support, it is depressingly likely that new chemistry will rapidly fall to fungicide resistance too and we need the existing products to remain working to help support the new.  These concerns are made worse by the imminent removal of the multisite chlorothalonil at the end of May 2020.

With so much risk attached to septoria and so much pressure on fungicides, the use of varietal resistance to help to reduce the risk of septoria has really come to the front and centre of growers minds.  The average septoria rating of wheat varieties being used on-farm has increased, coming on the back of these issues in managing the disease with a heavy reliance on fungicides.  There are many varieties to choose from but market demand will always be key. Winter wheat varieties with soft endosperm remain the most important choices for Scottish growers in meeting the needs of the grain distilling sector.

This summer’s list of soft Group 4 varieties for distilling and feed use includes the well-established Viscount, Leeds, Revelation, LG Motown and LG Sundance along with the more recently introduced KWS Jackal and Elation, and new varieties LG Skyscraper and LG Spotlight.  The disease ratings for these differ widely – so some older ones like Leeds is now weak on many fronts including mildew.  Of the newer ones, LG Sundance

Plots of Viscount at the SRUC trial site in East Lothian treated SDHI and azoles chemistry showing worryingly high levels of disease

has a septoria rating of 7.9, which is one of the best on the list for disease resistance.

LG Mowtown is intermediate at 5.9.  Some Group 3 biscuit making varieties such as Zulu and Elicit also suit distilling.  For hard feed wheat, newer varieties Gleam and RGT Gravity are the top choices, and a new hard milling variety KWS Extase has outstanding untreated yield and scores 8.1 for septoria which is right at the top end.  Gleam is intermediate and RGT Gravity weaker for septoria.  When making variety choices check for the best balance of disease resistance, maturity, straw stiffness and grain quality.

Check the disease ratings of varieties of interest and pick the best septoria rating you can for the market sector you are aiming at.  Yellow rust is another important one to check and can mean savings in terms of T0 chemistry but trial data from this season suggests please there may be new races about which might change the varietal ratings.  In trials in south-east Scotland and north of England, many varieties seem to have succumbed to yellow rust, even when rated with a good resistance score of 8 or 9.  The UK Cereal Pathogen Virulence Survey will report what new races have been detected this summer but the UKCPVS reports don’t usually come out until early the following year.   That doesn’t help variety choices just now so it makes sense to still pick the high rated ones now and then modify spray plans in March if there are significant risks to varieties now rated as good for yellow rust resistance but where later data shows they have shifted.

Fiona Burnett, SRUC, for the Farm Advisory Service

Plots of Viscount at the SRUC trial site in East Lothian treated with novel actives that will come to the market soon – septoria

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