Will the newly approvedSDHI Adexar, offer anything new or valuable to the barley fungicide”toolbox”?
AndrewGilchrist, MD of Scottish Agronomy is well placed to offer his view, having usedAdexar in the company’s trials since 2010. This year Adexar will be a keyrecommendation for both winter and spring barley, because earlier this year itreceived approval for brewing and malting, which makes it a realistic optionfor barley growers he suggests.
MrGilchrist sees the role of Adexar as a valuable addition to a market heavilyreliant on just one active ingredient, prothioconazole. “I’m uncomfortablewith one main active ingredient to rely on and until now Siltra has been ourmain option.
Prothioconazolehas been the mainstay of T1 sprays for many years but trials by ScottishAgronomy point to the SDHI chemistry offering from Adexar being a valuableoption if the T2 spray is likely to be delayed. For them, the most effective T2option has been consistently shown to be a triazole/SDHI combination.
“Thereis very little to split Adexar from Siltra, and I see Adexar as an alternativefit early or at T2 at a rate of 0.8-1 litre/ha,” he suggests.
Inone of Scottish Agronomy’s 2013 trials in Fife on the variety Cassia, the threestand-out programmes showed the heavy reliance on prothioconazole and theresponse from Adexar as an alternative:
Themost responsive treatment – a 4-spray programme of Kayak + Corbel at T0,Proline + Kayak + Bravo at T1, Siltra + Bravo at T2 and a further spray ofSiltra at T3
Thesecond most responsive, a 3-spay programme of Kayak + Corbel at T0, Proline +Bravo at T1 followed by Adexar + Bravo at T2
Thethird-ranking programme was 3-sprays of Kayak + Corbel at T0 followed Siltra +Bravo at T1 + T2.
Addingto Mr Gilchrist’s comments, Market Rasen based, independent agronomist RogerCowling says: “From a resistance management perspective, the continuedreliance on one barley fungicide is not a healthy situation and the approval ofAdexar is a chance to mix up the actives used for barley.
Withmore than 80% of the spring barley crops drilled in this area, we are lookingahead to what the season will bring in terms of disease. Crops are emergingwell and signs are that we will be fighting disease based on the current mildand wet conditions, irrespective of the variety.
Basedon this Mr Cowling will be recommending the use of Adexar at T1 at a rate of0.6 litre/ha with the addition of chlorothalonil. At T2 he will stay with theprothioconazole option.
BASFrecommendations for Adexar use in barley are slightly favoured towards higherdose rates of 0.75-1 litre/ha, and also advise that it is a very effectiveoption at T2 at the same dose rates. “We’d also recommend the inclusion ofa strobilurin somewhere within the programme such as Comet 200 to furthersupport resistance management,” says Jonathan Ball of BASF.
Theapproved dose for malting, set by the British Beer and Pub Association, is amaximum of 1 litre/ha Adexar (62.5g of the active ingredient Xemium per crop)at GS45 (just before ear emergence).