Varietal mix leads to high mildew risk in cereals

UK - January 31, 2007

Mildew is likely to be a problem this year in cereals due to the current varietal mix in wheat and barley and the increased interest in oats, together with the mild winter, warns Dow AgroSciences.

"All of the high risk factors for powdery mildew have come together this year - early drilling, mild winter and a lot of susceptible varieties being grown.  Three important winter wheat varieties, Solstice, Claire and Brompton have just a four when it comes to mildew susceptibility ratings and the new Group 4 Humber together with Istabraq and Richmond have a 5 rating.  Over half of the other varieties on the HCGA Recommended List 2007/2008 have a 6 rating.  Some wheats have been downgraded in terms of their mildew ratings.  Robigus had a 9 rating when it was launched and now has a 7.  Solstice had a 7 and is now a 6.  In fact eight of the current list of varieties have had their mildew ratings changed.  Breeders have been concentrating more on Septoria resistance and other end market characteristics rather than developing varieties that can withstand high levels of mildew," explains Liz Tomkinson, Fungicide Specialist for Dow AgroSciences.

"In winter barley three varieties have a 4 rating for mildew - Saffron, Cannock and Colussus- whilst Cassata, Camion, Spectrum and Siberia are rated as a 5 for this disease.  The leading winter barley Pearl has been downgraded from a 7 to a 6 and the 6-row Sequel from an 8 to a 6.  Winter oats, which are enjoying a revival as a result of the health kick, include varieties such as SW Dalguise with a 3 rating for mildew, Gerald, Ayr and Grafton with a 4 and Brochan with a 5 rating.  We now have a situation where a significant proportion of crops in the ground are prone to mildew," says Liz.

In addition, early drilling, the exceptionally mild winter with few, if any, frosts, and lush crops has resulted in high levels of mildew inoculum ready and waiting to attack.  Growers are advised to include a specific mildew fungicide such as Fortress (quinoxyfen) in their first fungicide spray in order to protect the crops from early infection.

Liz points out that even moderate levels of mildew left unprotected can cause a 5-10% yield loss and, as Fortress is one of the most cost-effective mildewicides on the market, its inclusion in the T0 spray will pay for itself many times over.  "Trials work shows that it is the early mildew that causes the greatest impact on yield.  A few pounds worth of Fortress is well worth putting in the spray tank with chlorothalonil or a triazole at T0 timing in order to protect the leaves from infection.  Fortress offers high degree of performance and protects the plant for up to eight weeks.  Its early use will also deliver the best margin over input costs."

Fortress contains 500 g/litre quinoxyfen, formulated as a suspension concentrate.  It is a systemic protectant fungicide giving protection against powdery mildew on new plant growth.  It is recommended on all varieties of winter and spring wheat, barley, oats, rye, triticale, durum wheat and sugar beet.  In cereals the dose rate is up to 0.3l/haIn cereals has a dose rate of 0.3l/ha, with a maximum total dose of 0.6 l/ha.  Fortress should be applied in the spring at first signs of disease up until Growth Stage 49.  It is rainfast in one hour and is packed in a 1 litre container.